Product Guides
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Rivet guns decoded: hand, lever, pneumatic, cordless and rivnut tools, mandrel-jam fixes, rivnut spin-failure recovery and brand selection for AU industry.
Read moreGrease Nipple & Zerk Fitting Guide: Sizes, Types & Threads
Need the right spanner for that bolt? Our Spanner Size Chart lists every common metric and imperial size. For tap selection by hole type and material, see our Tap Types Explained guide. For matching ratchet and socket kits, see our ratchets and sockets range. Looking for grease couplers? Our grease couplers range covers the common sizes and brands. For grease nipples, see our grease nipples range stocked across Australia.Grease nipples are usually a tapered thread into the housing, and a thread sealant on installation prevents grease weeping back out around the fitting under pump pressure. See our Loctite Thread Sealant Guide for grade selection. Grease nipples look simple — they're not. Four global thread standards in use, four body geometries, three materials, and a national split where the rest of the English-speaking world uses one system and Australia uses another. Get the thread wrong and you cross-thread the host casting permanently. Get the body geometry wrong and you can't fit a grease gun onto it. Get the material wrong and you snap the body installing it. This guide covers every thread standard, every body type, every blockage symptom, and the broken-nipple recovery workflow that gets you back to greasing instead of swearing. Common mistakes — failure modes table — Quick Reference Quick reference for grease nipple & zerk fitting guide, drawn from the detailed section below. Mistake What goes wrong Fix Cross-threading 1/8" BSP into 1/8" NPT host (or vice versa) Host casting thread stripped — host casting often unsalvageable without thread repair Always confirm thread before installing. Hand-thread 3 turns minimum without resistance. Over-torquing brass body nipple Body snaps at thread root, stub stuck in host Brass = 8-10 Nm max. Hand-spanner pull only, not a wrench. Forgetting thread sealant on parallel BSP threads Grease leaks past thread under pressure, fitting walks out under vibration PTFE tape or Loctite 577 on all parallel threads. NPT tapered doesn't need sealant. Installing wrong angle (straight where 90° needed) Grease gun coupler won't fit due to access constraints — wasted fitting Check the access angle before ordering. Angled fittings are inexpensive — order a variety pack. Hammering on a blocked nipple to clear it Internal spring damaged, ball valve deformed, body cracked Penetrating oil + tap/vibrate gently. Use Grease Buster tool for stubborn blockages. Specifying mild steel for marine/coastal use Nipple corrodes within 6-12 months, grease passages contaminate Stainless 316/A4 for any marine, food-grade, or coastal application. Modest premium. No grease nipple cap in dusty environment Dust pushed into bearing on first grease stroke after dust exposure Add caps to all exposed nipples on mining/agricultural/outdoor plant. Reusing a damaged nipple after extraction Ball valve compromised, leaks or fails to seal — bearing greasing unreliable Replace any nipple removed for any reason. They're $2-$3 each. Don't reinstall used. What is a grease nipple — and is it the same as a zerk fitting? A grease nipple is a small one-way valve threaded into a bearing housing, pivot pin, joint or moving part. When you attach a grease gun coupler to the nipple and pump the handle, fresh grease enters through the nipple and pushes old, contaminated grease out the other side of the bearing. A spring-loaded check ball seals the nipple between uses so dirt can't enter and grease can't escape. Is a zerk fitting the same thing? Yes. "Zerk" is the US name (after Oscar Zerk, who patented the pin-style fitting in 1929). "Grease nipple" is the Australian, British, European, South African and New Zealand name. Both terms refer to the same product class. AU industrial buyers call them grease nipples; American mechanics, agricultural and 4WD enthusiasts call them zerks. The ball end where the grease gun connects is universally the same dimension across all brands and thread types — only the threaded shank that screws into the host part varies. This guide uses "grease nipple" as the Australian standard term and flags "zerk" where US sources or AU 4WD/agricultural workshops use the import terminology. Both terms are correct. The four thread standards every AU workshop must know Grease nipple confusion is almost always thread confusion. There are four primary global thread standards in active use, and an AU workshop will encounter all four depending on what equipment comes through the door: Standard Where it dominates Common AU applications Identification 1/8" BSP / 1/4" BSP (British Standard Pipe, parallel) UK, AU, NZ, Europe Australian-made plant, agricultural machinery, garden tools, trailers, Australian-spec heavy equipment Parallel thread (no taper); 28 TPI on 1/8", 19 TPI on 1/4". Hex flats often 10mm or 14mm. 1/4"-28 UNF (Unified Fine, parallel) USA, Canada, US-imported automotive and heavy plant worldwide US-spec vehicles, US-built construction equipment, Holden/Ford old-spec, US heavy plant Parallel thread; 28 TPI; hex flats typically 11/32" (8.7mm). 1/8" NPT / 1/4" NPT (National Pipe Tapered) US plumbing-derived applications, US hydraulics US hydraulic cylinders, some US pumps, older US plumbing-grade pivots Tapered thread (visibly cone-shaped shank); 27 TPI on 1/8". Often confused with 1/8" BSP (28 TPI — 1 thread per inch difference). M6×1 / M8×1 / M10×1 / M10×1.25 / M10×1.5 (Metric) European OEMs (Mercedes, MAN, Volvo, Scania, BMW heavy plant) European trucks, European-spec construction equipment, modern European-engineered agricultural plant Parallel thread; metric pitch. Hex flats vary 8mm–13mm depending on size. The AU reality across most workshops: 1/8" BSP is the default for Australian-manufactured equipment, garden machinery, trailers, and most Australian-spec plant. 1/4"-28 UNF appears on automotive (especially older Holden/Ford), US-imported 4WD parts, and US-built heavy plant. M-thread metric shows up wherever European equipment is in service — increasingly common as European trucks and construction plant expand into the AU market. 1/8" NPT is least common but still seen on US hydraulic and pneumatic equipment. Workshop assortment kits like the Champion CA2415 Metric & Imperial Master Kit ($265.12), the Champion CA109 Metric Assortment Kit (105 pieces) ($88.35), the Champion CA108 Imperial Assortment Kit (113 pieces) ($105.66), and the GJ Works GKA144 144-piece Kit ($54.11) include sizes across all four standards specifically because no AU workshop avoids encountering all of them. BSP vs NPT — the apprentice trap that destroys host castings ⚠️ DO NOT CROSS-FIT 1/8" BSP AND 1/8" NPT 1/8" BSP is 28 TPI parallel. 1/8" NPT is 27 TPI tapered. They look almost identical to the eye. A 1/8" NPT nipple will thread two or three turns into a 1/8" BSP hole before galling, locking, and stripping the host thread permanently. Once damaged, the host casting often requires drilling out, tapping oversize, and fitting a Helicoil thread insert to recover. The forum-validated rule (Practical Machinist threads 145629, 245989, and 368040 plus AU industrial supplier consensus): if it doesn't spin in freely by hand for at least three full turns, stop. Wrong thread. The two thread families also seal differently: 1/8" NPT is tapered — the thread wedges itself into the host casting and seals on the thread interface itself as it tightens. No gasket required. 1/8" BSP is parallel (BSPP — British Standard Pipe Parallel) — the thread provides mechanical grip only. Sealing requires either a copper or fibre washer under the head, a small dab of thread sealant on the thread, or a tapered seat in the host casting (BSPT variant, less common in grease nipples). Cross-threading damage is the single most common host-casting failure in AU workshops. The fix is expensive — drill the hole oversize, tap M8 or M10, and fit an oversize Helicoil-style insert (see the Stripped Thread Repair Guide). Prevention is to identify the thread correctly before reaching for a wrench. Body geometry — straight, 45°, 67°, 90° The thread is one half of the selection decision. The body geometry — the angle at which the ball-end sits relative to the thread — is the other half, and it's driven entirely by access. Where there's room to swing a grease gun straight onto the nipple, a straight-body nipple works fine. Where there's no room — and on most modern equipment there isn't — you need an angled body to redirect the grease gun coupler to a usable angle. Geometry Body description Use when AIMS examples Straight (0°) Ball end pointing directly out from the thread axis Open access — pivot pins on swing arms, exposed bearings, workshop fittings. The default. Champion CN161 Straight M6×1 25/Pack, Champion CN3 1/4" UNF Straight 25/Pack, Lubemate Metric Straight Tapered, Champion CGN28 1/8" NPT 100/Pack ($62.50), Champion CGN29 BSP Straight ($58.88), Lubemate UNF Straight 45° Ball end angled 45° from thread axis Mid-restricted access — when straight access exists but at an awkward shoulder angle. Common on chain conveyors, mid-equipment pivots. Alemlube UNF 45° Grease Nipple ($2.55), Champion Grease Nipple Metric Refill 45° ($9.35), Champion 45° refill packs (metric + imperial) 67° Ball end angled 67.5° from thread axis Less common — used where 45° doesn't quite reach and 90° crowds another component. Specified by OEMs for specific applications. Champion Imperial Refill 67° ($7.41) 90° Ball end pointing perpendicular to thread axis Tight access — when the grease gun can only approach from a sideways angle. Common on modern excavator pins, articulated joints, undercarriage points. Alemlube UNF 90° Grease Nipple ($2.55), Champion C1808-13 M6×1 90° Stainless 10pk ($37.25), Champion 90° Metric ($25.81), Champion Grease Nipple Metric Refill 90° ($9.35), Champion Grease Nipple Imperial Refill 90° ($7.93) Practical workshop rule: stock straight, 45°, and 90° in each thread size you encounter regularly. The 67° fittings are usually OEM-spec — order on demand rather than stocking. The Champion refill packs ($6.76–$12.13 each) and the multi-angle assortment kits cover the everyday workshop spectrum. How to identify an unknown grease nipple An unmarked nipple from an unknown source — pulled out of a customer's vehicle, found in a parts bin, or stripped off a serviced asset — needs identifying before you order a replacement. The systematic approach: Look at the thread profile. If the threaded shank is visibly conical (wider at the head, narrower at the tip), it's NPT (tapered). If parallel, it's one of BSP, UNF, or metric. Measure the thread diameter with calipers — the major diameter at the head end. Common diameters: 1/8" BSP: 9.7mm major diameter 1/4" BSP: 13.2mm major diameter 1/4"-28 UNF: 6.35mm major diameter 1/8" NPT: 10.2mm major diameter at the head, tapering down M6×1: 6.0mm major diameter M8×1: 8.0mm major diameter M10×1: 10.0mm major diameter Count the threads per inch (TPI) or measure the pitch. A thread gauge is the fastest tool. 28 TPI on a 9.7mm parallel thread = 1/8" BSP. 27 TPI tapered = 1/8" NPT. 1.0mm pitch on an 8mm parallel thread = M8×1. The Metric vs Imperial Fasteners Guide covers thread identification in more detail. Check the hex flats. 1/8" BSP commonly has 10mm or 14mm hex flats. 1/4"-28 UNF has 11/32" (8.7mm). Metric M6/M8/M10 typically has 8mm, 10mm, or 12mm. This is a confirming check, not a primary identifier. Test-fit a known nipple from the assortment kit as a final confirmation before installing the replacement. The Workshop Buddy Metric Grab Kit (M6×1 to M10×1.5) ($33.33) and Imperial Grab Kit (1/8"-27 to 1/4"-28) ($33.33) are designed specifically for this — both kits include a test-fit selection across the common AU sizes for ~$67 total. Materials — mild steel, stainless steel, brass Grease nipple body material drives corrosion resistance, strength, and price: Material Installation torque Corrosion resistance Best for AIMS supply examples Mild steel zinc-plated 20–30 Nm Limited — surface protection only. Will rust in marine, salt-spray, or constant-wet environments after the zinc coating wears. Indoor workshop assets, dry environments, general industrial maintenance Champion CGN15 Straight ($64.54), Champion CGN29 BSP Straight ($58.88), most Alemlube / Lubemate standard products. Default supply. Stainless steel 316/A4 20–30 Nm Excellent — marine grade. Withstands salt spray, food-grade washdown, chemical exposure Marine, food processing, pharmaceutical, outdoor heavy plant, coastal applications Champion SSCN29 1/8" BSP Stainless 316/A4 25/Pack ($76.44), Champion SSCN Straight Stainless Steel ($35.95), Champion C1808-13 M6×1 90° Stainless 10pk ($37.25) Brass 8–10 Nm only (snaps above this) Moderate — won't rust but tarnishes. Not suitable for high-vibration applications. Low-pressure brass plumbing applications, decorative or non-load-bearing fittings Specialty — source on request The most common installation mistake is over-torquing a brass-body nipple. Brass bodies have roughly one-third the yield strength of steel and snap at the thread root when over-tightened. Practical Machinist forum consensus: torque brass to 8 Nm max (feel: a snug hand-spanner pull, not a wrench pull). Steel and stainless tolerate 20-30 Nm comfortably. For coastal Australia, marine industry, and food-grade processing, stainless 316/A4 is the only sensible specification. The premium over mild steel is modest (Champion SSCN29 stainless 25-pack at $76.44 vs CN29 mild steel equivalents at ~$58.88) and corrosion-driven failure costs vastly more than the upfront fitting cost. Button head fittings — high-pressure / hard-to-reach The standard grease nipple has a small ball-end designed for a standard push-on grease gun coupler. Button head fittings are an alternative geometry with a larger, flatter head designed for a dedicated button-head coupler. Two scenarios drive button-head selection: Hard-to-reach applications — the larger flat head accepts a coupler at a wider range of angles without slipping off. Excavator stick pins, articulated dump truck joints, and large agricultural equipment commonly use button heads on points where the operator can only approach the fitting from off-axis. High-pressure greasing — button heads handle higher line pressures (10,000+ psi capable) without coupler blow-off, making them the standard on assets serviced with high-pressure grease guns. See the just-published Grease Gun Guide for the high-pressure gun selection and the 10,000 psi vs 5,000 psi vs hand-pump rating breakdown. Button head fittings require a matching button-head coupler — a standard grease gun coupler won't grip a button-head fitting. Workshops that service mining or large construction plant typically keep both styles of gun ready, or use a Macnaught Lock-N-Lube-style universal coupler that accommodates both. AIMS stocks button head fittings in standard thread sizes — search /collections/grease-nipples for button head variants. Compatible button-head couplers and high-pressure grease guns are available in /collections/grease-guns alongside the Macnaught universal Lock-N-Lube range. For lubrication oil dispensing (engine oil, gear oil, hydraulic oil) rather than grease, see the Oil Pump & Drum Pump Guide covering Macnaught BOP battery, OILMASTER and R-SERIES air-operated drum pumps. Specialty heavy-mining button heads sourced on request through our supplier network. Contact us for OEM-spec mining/excavator button head fittings. Header blocks and central greasing Central greasing systems consolidate multiple grease points into a single accessible location via a header block — a manifold with one input port and multiple output ports that route grease to individual bearings through small-bore tubing. The Alemlube Header Block 5 Outlet Fittings and Grease Nipples 6135 ($103.28) is a complete 5-point central greasing manifold. Mount the block in an accessible workshop location, run small-bore copper or nylon line from each outlet to the target bearing, and you can service five hard-to-reach points from one easy-access nipple instead of climbing onto equipment to reach each one individually. The use cases: Heavy plant with multiple buried bearings — agricultural machinery, conveyors, large fans Confined-space machinery where bearings sit behind guards, panels, or in unsafe-access positions Production-line equipment requiring scheduled multi-point greasing on shutdown — central greasing reduces the per-cycle labour from 30 minutes (climbing, removing guards, accessing each point) to 5 minutes (one technician at the manifold) For workshops servicing assets with more than 5–6 grease points, full automatic central greasing systems (electric pumps + distribution manifolds + timer controllers) become viable. Header blocks are the manual-pump entry tier. How to install a new grease nipple correctly Whether replacing a broken nipple or fitting a new one to a custom assembly, the workflow: Confirm the existing thread (if replacing). Wrong thread = host casting damage. See the identification section above. If drilling and tapping a new hole: drill to the tap drill size for your chosen thread. Common drill/tap pairs: 1/8" BSP = 8.8mm drill / R 1/8" tap. 1/4"-28 UNF = 5.5mm drill (#3 letter drill) / 1/4"-28 UNF tap. M6×1 = 5.0mm drill / M6×1 tap. M8×1 = 7.0mm drill / M8×1 tap. The Tap & Die Guide covers tapping technique. Tap straight — perpendicular to the surface. An off-axis tap creates an off-axis fitting that the grease gun coupler won't engage cleanly. Clean the new thread with compressed air or a thread-clearing pick to remove swarf. Swarf inside the thread will gall the nipple as you fit it. Apply thread sealant or PTFE tape on parallel threads (BSP, UNF, metric). NPT tapered threads typically don't need sealant. See the Thread Locking & Sealing Guide for sealant selection — Loctite 577 or 567 for high-pressure applications, PTFE tape for general workshop work. Hand-thread the nipple in for at least 3 full turns. If you feel resistance in the first 2 turns, stop — wrong thread or cross-threading. Back out, check, re-confirm. Wrench-tighten to 20-30 Nm for steel/stainless, 8-10 Nm for brass. A small open-ended spanner is the right tool — not a socket wrench, which over-torques easily. Test with the grease gun — attach the coupler, pump 2-3 strokes. Grease should enter without back-pressure. Disconnect cleanly. Wipe excess grease off the fitting and surrounding surface. For high-vibration applications (excavator pins, agricultural drawbar pivots, rotary equipment) add a small dab of Loctite 243 medium-strength threadlocker on the thread before installation. This prevents the nipple from backing out under vibration without preventing future removal. Why won't my grease nipple take grease? — 6 diagnostic steps A grease nipple that won't accept grease is the #1 maintenance frustration. The systematic diagnostic: Confirm the grease gun itself is working. Disconnect the coupler from the nipple and pump the handle — grease should emerge from the coupler. If not, the gun is the problem (empty cartridge, blocked feed, air-locked priming — see the Grease Gun Guide diagnostic). Confirm the coupler is fully engaged. A loose coupler engagement vents grease around the connection rather than into the nipple. Push the coupler firmly onto the nipple ball — you should hear or feel a slight click. If the ball end is dirty, contaminated grease prevents seal. Wipe clean and re-try. Test the nipple ball valve with a small nail. A 16-gauge nail or pick depressed against the ball should move freely. If the ball is stuck, the internal mechanism is fouled — see the unblocking section below. Check for back-pressure. If the grease gun handle gets harder and harder to pump but no grease moves into the nipple, the back-pressure is downstream — the bearing cavity itself may be full of contaminated grease that won't compress further, or the bearing's relief path is blocked. Solution: continue moderate pressure, allow time for the bearing to relieve, or in extreme cases dismantle and clean. Verify the bearing has a grease path. Some sealed bearings appear to have a grease nipple but the bearing internal cavity is fully sealed — the nipple is decorative or non-functional. Common on small budget machinery imported from low-cost markets. Check the equipment service manual. Check for contaminated grease in the nipple. If old hardened grease has solidified inside the nipple body itself (not the bearing cavity), grease physically can't move through. See the unblocking section. Clearing a blocked grease nipple If diagnosis points to a blocked nipple (gun works, bearing cavity has grease path, but the nipple itself won't accept grease), four field techniques in order of escalation: The rag trick (Dorman Shop Press technique). Fold a thin rag (old t-shirt cotton) over the nipple. Press the grease gun coupler firmly onto the nipple through the rag. The rag creates a better seal and applies even pressure to the ball valve. Pump 3-4 strokes. Often releases mild contamination on the ball. The 16d nail trick (universal forum consensus). A 16-gauge nail or pick tip depressed firmly against the centre ball of the nipple, used to physically dislodge contamination. Forum threads from Snowblower Forum, MyTractorForum, and Practical Machinist consistently report this resolves "about 90% of stuck-ball" cases. Wipe excess clean before retrying with the grease gun. Penetrating oil + back-and-forth pin rotation. If the ball valve mechanism itself is seized (not just dirty), apply penetrating oil to the ball end, work the ball back and forth with a pin or nail tip until it moves freely. Wait 15-20 minutes for the penetrant to wick into the spring mechanism. Re-try the grease gun. Heat application + immediate grease. Warm the nipple body briefly with a propane torch (5–10 seconds, not red-hot). The heat thins the hardened grease inside the nipple. Immediately attach the grease gun and pump while the body is still warm. The thinned grease pushes out, fresh grease pushes in. Use sparingly — repeated heat-cycling can degrade the nipple's spring temper. If all four techniques fail, the nipple is mechanically failed (broken spring, deformed body) and needs replacement. The Grease Buster-style dedicated tool (penetrating oil reservoir + impact piston) handles severe cases without damaging the nipple body — useful where the nipple is in a position you can't easily replace. How to remove a broken grease nipple A snapped grease nipple — head broken off flush with the host surface, or partial thread shear leaving a stub in the casting — requires extraction. The good news: grease nipple bodies are mild steel (or stainless), much softer than hardened bolts. Extraction is usually straightforward. Apply penetrating oil to the broken stub. Allow 20 minutes minimum for the oil to wick into the thread. If a stub protrudes: grip with locking pliers (Vise-Grip style) and rotate counterclockwise. Many broken nipples back out at this stage without any extractor needed. If flush with surface or below: centre punch the broken nipple. Drill a small pilot hole (2.5mm-3mm) into the centre. Use a screw extractor (Easy-Out) at #1 or #2 size — see the just-published Bolt Extractor Guide for the combined left-hand drill + extractor workflow. For really stubborn nipples: drill the entire body out to the tap drill size for the thread, then re-tap the original thread to clean it up. The Bordo or Sutton M603S20L combined left-hand drill + extractor sets handle this in 5 minutes. If the thread is damaged during extraction: follow the Stripped Thread Repair Guide — drill oversize, tap M-larger, and fit a Helicoil thread insert. Avoid hammering or applying side-load to the broken stub. Grease nipple bodies are softer than the host casting but the host thread is the part you're trying to preserve — damaging the host thread is far more expensive than the $2 nipple. Grease nipple caps — when dust protection matters A grease nipple cap is a small dust cover that snaps over the ball end of the fitting. The Champion CGNC10 Grease Nipple Cap ($13.93) is the AIMS workshop default. Caps protect the ball end between greasing intervals — without one, the nipple ball is exposed to dust, water, and chemical contamination. Buy in bulk packs from /collections/grease-nipples. Caps matter most in three scenarios: Dusty environments — mining, quarrying, agriculture, construction sites. Dust accumulates on the ball end between greasing intervals, and the first grease gun stroke pushes contamination directly into the bearing. The cap blocks contamination at the source. High-pressure water washdown — food processing, marine, dairy. Water under pressure forces past the ball valve into the bearing cavity, displacing grease and accelerating corrosion. Caps with O-ring seals are mandatory for these applications. Long service intervals — equipment greased monthly or quarterly. The longer the gap between greasing, the more dust accumulates, and the higher the contamination risk per service. For most general workshop environments — indoor maintenance, dry industrial — caps are optional. For mining, marine, food processing, agricultural and outdoor heavy plant they should be standard fitment. Selection guide — workshop kit vs OEM-spec replacement Two distinct purchase scenarios drive different product selection: Scenario 1: Workshop assortment for general maintenance. You service a mix of equipment — agricultural, automotive, plant — and need ready access to common sizes. Buy assortment kits: Light workshop: Workshop Buddy Metric Grab Kit M6-M10 ($33.33) + Workshop Buddy Imperial Grab Kit 1/8-1/4 ($33.33). $67 covers most common AU sizes. Mid workshop: GJ Works GKA144 144-piece Kit ($54.11) — broader range, single case. Production / fleet workshop: Champion CA2415 Metric & Imperial Master Kit ($265.12) — comprehensive, includes premium stainless, fits the daily-use serviceable workshop. Scenario 2: OEM-spec replacement. You've identified an exact fitting type, size, and geometry, and need replacement-spec only: Bulk replacement (10-25 of one type): Champion CN-series 25/packs ($11.82–$76.44), perfect for fleet servicing where you replace nipples on a schedule. Single replacement: Alemlube individual refills ($2.55–$3.50) — buy one of the exact spec. Refill packs for trade box: Champion Refill packs ($6.76–$12.13) — 10-piece packs in straight, 45°, 67°, 90° for replenishing your trade box. Marine / food-grade replacement: Champion SSCN-series stainless 316/A4 ($35.95–$76.44 per pack) — non-negotiable for these environments. AIMS supply — Champion, Alemlube, Lubemate, Workshop Buddy, GJ Works AIMS stocks 160+ unique grease nipple SKUs across five vendors in /collections/grease-nipples — the deepest grease nipple supply position in AU industrial distribution outside the specialty lubrication trade. Vendor profile: Vendor Range depth Strengths Best for Champion 68 SKUs Comprehensive — refill packs, bulk packs (25/100 packs), assortment kits, stainless steel, all thread types, all geometries, grease nipple caps Trade workshop, fleet maintenance, multi-thread assortment Alemlube 60 SKUs Individual fittings priced for low-quantity replacement ($2.55+), header blocks, central greasing components, BSP focus Single-fitting replacement, central greasing system builds Lubemate 29 SKUs Mid-tier between Alemlube and Champion. Tapered metric thread specialty. Workshop trade box, mid-volume use Workshop Buddy 2 grab kits Compact 110-piece grab kits covering metric and imperial sizes ($33.33 each) Mobile mechanic, service ute, on-site repair GJ Works 1 master kit GKA144 144-piece kit ($54.11) — broad single-case assortment Trade workshop entry-level master kit Browse the complete range at /collections/grease-nipples. For grease guns, couplers and high-pressure equipment to use with these fittings see /collections/grease-guns and the Grease Gun Guide. For lubricants and grease selection see /collections/greases and the Grease Types & Selection Guide. Honest scope: AIMS doesn't stock Tecalemit (UK premium specialty), Lincoln Industrial (US specialty branded), or Stauff (German central greasing). These specialty brands are available through our supplier network on request — contact us if you need a specific brand-spec replacement for European or US heavy plant. Common mistakes — failure modes table Mistake What goes wrong Fix Cross-threading 1/8" BSP into 1/8" NPT host (or vice versa) Host casting thread stripped — host casting often unsalvageable without thread repair Always confirm thread before installing. Hand-thread 3 turns minimum without resistance. Over-torquing brass body nipple Body snaps at thread root, stub stuck in host Brass = 8-10 Nm max. Hand-spanner pull only, not a wrench. Forgetting thread sealant on parallel BSP threads Grease leaks past thread under pressure, fitting walks out under vibration PTFE tape or Loctite 577 on all parallel threads. NPT tapered doesn't need sealant. Installing wrong angle (straight where 90° needed) Grease gun coupler won't fit due to access constraints — wasted fitting Check the access angle before ordering. Angled fittings are inexpensive — order a variety pack. Hammering on a blocked nipple to clear it Internal spring damaged, ball valve deformed, body cracked Penetrating oil + tap/vibrate gently. Use Grease Buster tool for stubborn blockages. Specifying mild steel for marine/coastal use Nipple corrodes within 6-12 months, grease passages contaminate Stainless 316/A4 for any marine, food-grade, or coastal application. Modest premium. No grease nipple cap in dusty environment Dust pushed into bearing on first grease stroke after dust exposure Add caps to all exposed nipples on mining/agricultural/outdoor plant. Reusing a damaged nipple after extraction Ball valve compromised, leaks or fails to seal — bearing greasing unreliable Replace any nipple removed for any reason. They're $2-$3 each. Don't reinstall used. Frequently Asked Questions What is a grease nipple and what does it do? A grease nipple is a small one-way valve threaded into a bearing housing, pivot pin, or moving part. When a grease gun coupler attaches and pumps grease through, the nipple's internal spring-loaded ball valve opens to admit fresh grease and closes between strokes to prevent grease escape and dirt ingress. The nipple allows scheduled relubrication without dismantling the bearing. Is a zerk fitting the same as a grease nipple? Yes — same product, different name. "Zerk" is the US term (after Oscar Zerk, who patented the design in 1929); "grease nipple" is the Australian, British, European and New Zealand term. Both refer to the same one-way valve fitting. AU industrial buyers use "grease nipple"; 4WD and agricultural buyers from US-influenced supply chains sometimes use "zerk." The product is identical. What thread size is a standard grease nipple in Australia? 1/8" BSP is the dominant standard on Australian-manufactured equipment, garden machinery, trailers, and AU-spec plant. 1/4"-28 UNF is common on automotive (especially older Holden/Ford) and US-imported 4WD. M-thread metric (M6×1, M8×1, M10×1) appears on European-built equipment. 1/8" NPT shows up on US hydraulic equipment. AU workshops typically stock all four standards because all four appear regularly. How do I tell BSP from NPT grease nipples? 1/8" BSP has 28 threads per inch with a parallel shank (cylindrical, same diameter top to bottom). 1/8" NPT has 27 threads per inch with a tapered shank (visibly cone-shaped, wider at the head than the tip). A thread gauge confirms TPI in seconds. They look almost identical — 1/8" BSP at 28 TPI vs 1/8" NPT at 27 TPI — and cross-threading damages the host casting. Hand-thread the nipple three turns minimum; if you feel resistance, stop and re-verify. What's the difference between metric and imperial grease nipples? Imperial (1/8" BSP, 1/4"-28 UNF, 1/8" NPT) measures in inches and TPI. Metric (M6×1, M8×1, M10×1) measures in millimetres and pitch in millimetres. The two systems are not cross-compatible — an M6×1 nipple won't fit a 1/4"-28 UNF hole even though they're similar sizes. Always match metric-to-metric and imperial-to-imperial. Champion CA2415 master kit and similar assortment kits include both systems for AU workshops servicing mixed equipment. Are all grease nipple ball ends the same size? Yes. The ball end where the grease gun coupler attaches is universally the same dimension across all standard grease nipples regardless of thread type or angle. A standard grease gun coupler fits a 1/8" BSP nipple, a 1/4"-28 UNF nipple, a M6×1 nipple, and a 1/8" NPT nipple identically. The thread is purely how the nipple fits into the host casting; the coupler end is global standard. Button head fittings are the exception — they have a larger flat head and require a dedicated button-head coupler. Why won't my grease nipple take grease? Six possible causes: (1) grease gun itself is empty or air-locked, (2) coupler not fully engaged on the ball, (3) ball valve in nipple is stuck with contamination, (4) bearing cavity is full and back-pressure prevents further grease entry, (5) bearing is internally sealed and the nipple is decorative/non-functional, or (6) hardened grease has solidified inside the nipple body itself. Diagnose in that order — gun → coupler → ball → cavity → bearing path → nipple body. How do I unblock a grease nipple? Four techniques in escalating order: (1) the "rag trick" — fold a thin rag over the nipple and press the coupler through it for better seal; (2) the "16d nail" trick — depress the ball valve with a nail or pick tip to dislodge contamination (works 90% of stuck-ball cases per forum consensus); (3) penetrating oil plus gentle back-and-forth ball-pin rotation; (4) heat the nipple body briefly with a propane torch then immediately attach the grease gun. If all four fail, replace the nipple. Can I remove a broken grease nipple without damaging the casting? Yes, usually. Grease nipple bodies are mild steel — much softer than hardened bolts. Apply penetrating oil, wait 20 minutes. If a stub protrudes, grip with locking pliers and turn counterclockwise — many back out at this stage. If flush or below: centre punch, drill a 2.5-3mm pilot hole, use a #1 or #2 screw extractor (Bordo or Sutton Easy-Out). See the Bolt Extractor Guide for the full extraction workflow. Replace any nipple after removal — don't reinstall used. What's a button head grease nipple and when do I use one? A button head fitting has a larger, flatter head designed for a dedicated button-head coupler. Used in two scenarios: hard-to-reach applications where the coupler needs to engage from off-axis (excavator pins, articulated joints, large agricultural equipment), and high-pressure greasing applications (10,000+ psi capable) where standard couplers can blow off under pressure. Button heads require a matching coupler — a standard grease gun coupler won't work. Common on heavy plant and mining equipment. Should I use stainless or brass grease nipples outdoors? Stainless 316/A4 — every time. Stainless handles marine salt-spray, food-grade washdown, chemical exposure, and outdoor weather. Brass tarnishes and has low torque tolerance (snaps at 8-10 Nm). Mild steel zinc-plated works for dry indoor workshops but rusts in marine, coastal, or wet environments within 6-12 months. The Champion SSCN-series stainless 316/A4 range costs modestly more than mild steel — a few extra dollars per pack — and prevents corrosion-driven failure that costs orders of magnitude more. What torque should I use to install a grease nipple? Steel and stainless steel: 20-30 Nm — a firm hand-spanner pull with a 10mm or 14mm open-ended spanner. Brass: 8-10 Nm only — a snug spanner pull, not a wrench pull. Brass snaps at the thread root if over-torqued. Always use an open-ended spanner, not a socket wrench, which over-torques easily. Hand-thread three turns minimum first — if resistance during initial threading, you have the wrong thread and need to stop. Why does my grease gun coupler keep popping off? Three common causes: (1) coupler not fully engaged on the ball — push firmly until you feel a slight click; (2) ball end of the nipple is contaminated or damaged — wipe clean or replace the nipple; (3) line pressure is too high for a standard coupler (over 5,000 psi) — switch to a button head fitting + button-head coupler, or use a Lock-N-Lube-style locking coupler that mechanically grips the ball rather than relying on spring tension. See the Grease Gun Guide for coupler selection. Do I need a thread sealant on a grease nipple? Parallel threads (1/8" BSP, 1/4"-28 UNF, M6×1, M8×1, M10×1) need either PTFE tape, a copper/fibre washer, or anaerobic thread sealant (Loctite 577 or 567) to seal — the parallel thread itself doesn't seal against grease pressure. Tapered threads (1/8" NPT) seal on the thread interface itself and don't strictly need sealant, though many workshops apply PTFE tape as a precaution. Always seal parallel threads; tapered threads are optional. What's the difference between 45° and 90° grease nipples — does it matter which I use? Yes — angle determines access. A 45° fitting redirects the ball end 45° from the thread axis; a 90° fitting redirects it 90° (perpendicular). On a tight bearing where the grease gun can only approach from a specific angle, the wrong fitting geometry means the coupler can't engage. Workshop assortment kits include straight, 45°, and 90° in each thread size precisely because access varies. Check the access angle before ordering, or stock all three angles to handle any situation.
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Bolt Extractor Guide: Easy-Outs, Spiral Flute & Sockets
Bolt extractors: spiral fluted, square, multi-spline and bolt extractor sockets compared. Left-hand drills, hardened-bolt failure mode and weld-a-nut technique.
Read moreShoulder Bolt Guide: Sizes, Specifications and Applications
Shoulder bolts: ISO 7379 sizing, Grade 12.9 alloy steel, H7/h6 shoulder fit, pivot vs spacer applications, and metric vs imperial selection guide.
Read moreRoll Pin Guide: Types, Sizes, Installation & Removal
What Is a Roll Pin?A roll pin is a hollow, cylindrical fastener with a single longitudinal slot running the full length of its body. It is made from spring steel — formed into a cylinder that is slightly larger in diameter than the hole it is designed to fit. When you drive the pin into the hole, the slot closes under compression and the outer surface of the pin bears against the hole wall, creating an interference fit that holds the pin firmly in place without any threads, adhesive, or additional retention hardware.The working principle is straightforward: the pin is oversized, the hole is at nominal diameter, and the spring force of the compressed steel keeps the pin retained. It cannot vibrate out, it will not back off under load, and it requires no precision tolerancing in the hole — a standard jobber-drilled hole at nominal diameter is all that is needed.Roll pins are used wherever you need to lock a component to a shaft, create a pivot point, or retain a part in a fixed axial position. The most common application is securing gears, pulleys, sprockets, and levers to shafts — the pin passes through aligned holes in both the shaft and the component, locking them so they rotate or move together. They appear in agricultural machinery, industrial gearboxes, automotive linkages, conveying equipment, and general maintenance workshops across Australia.For a general overview of pin fastener types — including split pins, cotter pins, and clevis pins — see the Split Pin and Cotter Pin Guide and the Clevis Pin Guide.One Pin, Five NamesIf you have worked in the Australian trade for any length of time, you have heard roll pins called several different things. They are all the same product. Understanding the names matters: when you are at a fastener counter, all five of these terms might be used interchangeably by the person serving you, or printed on the packaging.Roll PinThe most widely used term in Australia and internationally. It describes how the pin is made: a flat sheet of spring steel, rolled into a cylindrical shape with the two edges forming the characteristic longitudinal slot. This is the term you will find in most supplier catalogues and engineering standards documentation.Spring PinThe technically correct generic term. A spring pin is any pin that uses spring force to retain itself in a hole — this covers both slotted and coiled designs. In practice, "spring pin" and "roll pin" are used interchangeably for the slotted type. The DIN and ISO standards use "spring pin" as the governing term. If a drawing specifies "spring pin" without further qualification, confirm whether slotted or coiled is intended before ordering.Sellock Pin / Selock Pin / Sel-LokA widely used Australian and UK trade name. "Sellock" — also spelled "selock," "sel-lok," or "sellok" — originated as a brand name and became genericised in the Australian hardware and fastener trade, in the same way "Biro" became the common word for a ballpoint pen. If a boilermaker, fitter, or maintenance tradie asks for a sellock pin in an Australian workshop, they want a standard metric roll pin. The Blackwoods catalogue lists them as "Pin Roll Spring Sel-Lok ZP." United Fasteners calls them "Sellock Spring Pins." Cost Less Bolts lists them as "Sel-Lock Spring Pin Metric." Different labels — exactly the same product.The term "sellock" carries particularly strong commercial intent in online searches — search data shows it attracting click costs of over $110 per click on paid search, reflecting the high purchase intent of people who use that specific trade vocabulary.Tension PinAnother name for the slotted spring pin, particularly common in North American industrial literature. The name refers to the working principle: the compressed pin creates radial tension against the hole wall. You will encounter this term in ASME B18.8.2 (the US imperial standard) and in some Australian engineering drawings that follow US conventions.Slotted Spring PinThe fully descriptive technical name: a spring pin, of the slotted (single-slot) variety. This distinguishes it explicitly from the coiled spring pin (covered in the next section). When a specification reads "slotted spring pin," it means this product — not a coiled type. The two are not interchangeable in all applications, and their dimensional and performance characteristics differ.Slotted vs Coiled Spring Pins: What is the Difference?There are two distinct types of spring pin on the market. They look superficially similar and serve the same fundamental purpose, but they have meaningfully different performance characteristics. Getting this right matters in applications that see sustained vibration, shock loading, or repeated assembly and disassembly cycles.Slotted Spring Pin (Roll Pin) — DIN 1481 / ISO 8752A single flat sheet of spring steel, rolled into a near-complete cylinder with one longitudinal slot. The cross-section is an open circle — a C-shape — with the two sheet edges forming the slot gap. When compressed into a hole, the slot closes partially and the outer cylindrical surface bears against the hole wall with high contact stress along the full length of the pin. This creates the interference fit that retains the component.Slotted spring pins are the economical standard for the majority of applications: single-direction or moderate loading, low-to-moderate vibration, and assemblies that are installed once and rarely disassembled. They are slightly stiffer than coiled pins and develop a higher initial radial force, which gives them excellent retention in standard drilled holes. They are the default choice in most Australian maintenance workshops.Limitations: In high-fatigue applications — repeated shock loading, sustained vibration, or cyclic stress — the single-wall cross-section can initiate a fatigue crack at the slot corners over time. These corners are the highest stress-concentration points in the pin geometry. Slot orientation also materially affects service life: installing a slotted pin in the wrong rotational orientation can reduce its useful life by up to 50%. For applications where these limitations matter, coiled pins are the upgrade path.Coiled Spring Pin (Spiral Pin) — DIN 1482 / ISO 8750A coiled spring pin is made from a strip of spring steel coiled approximately 2.25 turns around its axis. The result is a multi-layer cylinder: the cross-section shows two or more overlapping walls rather than a single wall. This fundamentally changes the performance profile.Because the coils can flex independently of each other, a coiled pin distributes load and radial force across multiple contact points simultaneously. Shock and vibration are absorbed far more effectively than with a slotted pin. There is no single stress-concentration point analogous to the slot corners on a slotted pin — fatigue resistance is substantially higher as a result.Key advantages of coiled pins: No slot orientation requirement: Because load is distributed symmetrically around the multi-coil cross-section, a coiled pin performs identically regardless of its rotational orientation during installation. A significant practical advantage in rapid-assembly production environments. Reusable in the same hole: Coiled pins can be removed and reinstalled in the same hole because the coil spring-back is consistent and the pin does not flare or deform during removal the way a slotted pin sometimes can. Better vibration and shock resistance: The multi-coil geometry damps micro-movement under vibration more effectively than the single-wall slotted design. When to choose coiled over slotted: high-vibration environments (agricultural machinery, mining equipment, drivetrains); applications with repeated assembly and disassembly; shock-load situations; and wherever pin fatigue life is a design concern. Coiled pins cost more than slotted pins — for most standard maintenance applications, slotted pins are sufficient.Interchangeability note: Slotted and coiled pins to the same nominal diameter and length have the same external dimensions and fit the same hole. They are dimensionally interchangeable for a direct replacement. However, their spring rates and radial forces differ — for a critical application, check the original specification before substituting one type for the other.Roll Pin MaterialsMost roll pins are carbon spring steel. For most applications that is all you need — but there are situations where material choice matters significantly. Getting it wrong causes corrosion, contamination, premature failure, or regulatory non-compliance in food and pharmaceutical applications.Carbon Spring Steel (Standard) — Zinc-PlatedTypically 1070 or equivalent high-carbon spring steel. Strong, elastic, good fatigue resistance, and the default choice for the vast majority of industrial, agricultural, and mechanical applications. Carbon steel roll pins are standardly supplied zinc-plated — bright zinc or yellow-chromate passivated — which provides a base level of corrosion protection for indoor and dry conditions. The zinc plating is not a heavy corrosion barrier: it is not suitable for outdoor long-term exposure, marine environments, or wet-process industrial plant without a material upgrade. Stainless Steel — Grade 420 (Most Common) or Grade 304Used where corrosion resistance is required: food processing equipment, marine hardware, outdoor and agricultural machinery exposed to weather, pumps handling corrosive media, and any application where the pin is in regular contact with moisture, cleaning chemicals, or salt. Grade 420 (martensitic stainless) provides better spring properties than austenitic grades and is the standard stainless choice for spring pins. Grade 304 is available for more aggressive environments. Stainless spring pins carry a significant cost premium over carbon steel and are less universally stocked; for critical applications, allow extra sourcing lead time. Alloy Steel (Hardened and Tempered)Used in very high shear and shock-load applications where standard carbon spring steel performance is insufficient. Less common in everyday maintenance work, but specified in heavy drivetrain applications, mining equipment, and high-cycle machinery where pin failure would cause significant consequential damage. Not a standard stock item — typically sourced to order.DIN 1481 / ISO 8752: Understanding the StandardMetric roll pins in Australia are manufactured and specified to DIN 1481 (the German industrial standard) or its direct equivalent ISO 8752. In practice these two standards describe the same product to the same dimensions, and the terms appear interchangeably on supplier datasheets and engineering drawings. ASME B18.8.2 is the equivalent US imperial standard, relevant when working on American-designed machinery.How to Read the DesignationA full DIN 1481 designation reads: Spring Pin DIN 1481 – 5 × 30. Breaking that down: DIN 1481 is the governing standard; 5 is the nominal pin diameter in millimetres; 30 is the pin length in millimetres. A 5 × 30 pin is 5 mm nominal diameter and 30 mm long. The actual manufactured diameter will be slightly larger than 5 mm — the standard specifies an oversized range so the pin compresses on insertion. For coiled pins, the governing standard is DIN 1482 / ISO 8750, with the same designation format.Hole ToleranceDIN 1481 specifies a hole tolerance of H13 or H14 at the nominal diameter. This corresponds to a relatively wide tolerance — the kind produced by a standard jobber drill bit drilling into steel without reaming. This is by design: roll pins work in standard drilled holes. This is the critical differentiator from dowel pins, which require a precision H7 reamed hole. If you are replacing a dowel pin with a roll pin, the existing hole is acceptable as-drilled. If you are replacing a roll pin with a dowel pin, the hole will need to be reamed to H7 tolerance.Chamfered EndsAll DIN 1481 spring pins have chamfers at both ends. The chamfer guides the pin into the hole mouth without the edge catching. Either end can go in first — there is no designated entry end on a standard roll pin.Roll Pin Sizes: Diameter, Length and Drill Size ChartThe most common question when ordering roll pins is: what drill size do I need? The answer is simple: drill the hole to the nominal pin diameter. A 5 mm roll pin goes into a 5 mm hole. The pin is manufactured oversize and will compress on entry. You do not drill undersize; you do not ream the hole. Nominal Dia (mm) Drill Size (mm) Approx Mfg OD Range (mm) Common Lengths (mm) Typical Use 1.5 1.5 1.55–1.65 6, 8, 10, 12 Small precision mechanisms, instruments 2 2 2.06–2.20 8, 10, 12, 16, 20 Light mechanisms, hinges, small shafts 2.5 2.5 2.57–2.72 10, 12, 16, 20 Light machinery, small pivots 3 3 3.08–3.24 10, 12, 16, 20, 25, 30 General machinery, bicycle components 4 4 4.10–4.30 12, 16, 20, 25, 30, 36 Gearboxes, agricultural equipment 5 5 5.12–5.35 16, 20, 25, 30, 36, 40, 50 Most common size — general engineering 6 6 6.14–6.42 20, 25, 30, 36, 40, 50, 60 Shafts, sprockets, medium-duty pivots 8 8 8.18–8.50 25, 30, 36, 40, 50, 60, 80 Heavy shafts, drivetrain components 10 10 10.22–10.60 30, 36, 40, 50, 60, 80, 100 Heavy-duty industrial machinery 12 12 12.26–12.72 40, 50, 60, 80, 100 High-load shaft retention Oversized hole warning: If the drilled hole is oversized beyond H14 tolerance, the pin will not develop sufficient radial force. The pin will be loose and may vibrate free or fail to transmit torque reliably. If the pin slides in by hand without resistance, the hole is too large. Options: use the next size up pin, bush the hole and re-drill, or switch to a precision dowel pin with a reamed close-tolerance hole.Pin length selection: For a through-pin locking a hub to a shaft, the pin length should equal or slightly exceed the outer diameter of the hub. Drive to flush or 0.5–1 mm below the outer surface. Protruding pins catch on housings and interfere with adjacent rotating components. Recessed pins are acceptable for most applications.How to Install a Roll PinRoll pin installation has a few critical details that tradespeople regularly get wrong. The two most common — wrong punch type and wrong slot orientation — are easy to avoid once you know what to look for.Tools Required Dedicated roll pin punch: A roll pin punch has a small raised nub on the driving face. This nub seats on the outer rim of the hollow pin and drives it from the wall — not from inside the bore. Do not use a standard flat-faced punch. A flat punch of the same diameter as the pin, or any punch smaller than the pin OD, can enter the hollow bore and splay the pin walls outward. Once expanded, the pin seizes in the hole and is effectively impossible to remove without destroying it and the bore. This is the most common and most preventable roll pin mistake. Always use a dedicated roll pin punch. Hammer or arbor press: A hammer works for most installations. An arbor press gives more controlled vertical entry and is preferred for tight assemblies and production environments. Light lubricant (optional): A small amount of machine oil on the pin OD eases installation in tight holes. Use food-safe lubricant for food-adjacent applications. Step-by-Step Installation Drill the hole to the nominal pin diameter. For a 5 mm pin, use a 5 mm drill bit. No reaming required. Deburr the hole mouth if there is a raised burr from drilling. A sharp burr can deflect the pin on entry. Align the component and shaft so the holes are concentric and fully in-line. For slotted pins: set the slot orientation before driving (see section below). Present the pin chamfered end first into the hole mouth. Position the roll pin punch on the rim of the pin and confirm the nub is seated on the outer rim, not inside the bore. Drive the pin with controlled, progressive hammer blows. Do not use a single heavy strike — progressive driving keeps the pin aligned. Drive to flush or 0.5–1 mm below the surface. Do not leave the pin protruding. Slot Orientation: Why It MattersThis is the most underappreciated technical detail in roll pin installation, and it causes a disproportionate number of premature fatigue failures.In a slotted spring pin, the slot is the structural weak point. The pin's bending stiffness is lowest in the plane through the slot opening. If the primary load acts through that plane, the pin flexes more and increases bending stress at the slot corners — the fatigue crack initiation sites. Engineering data shows that a slotted pin with the slot parallel to the primary load direction can have service life reduced by up to 50%.The rule: orient the slot perpendicular to the primary load direction. For a shaft-to-hub connection locking a gear, pulley, or sprocket: orient the slot so it faces toward and away from the shaft axis — perpendicular to the shaft centreline, not along it. For a pivot pin with primarily bending load: orient the slot at 90° to the bending load direction.Coiled spring pins require no orientation. The multi-coil cross-section distributes load symmetrically. For applications where slot orientation is difficult to control during assembly, coiled pins eliminate the requirement entirely.How to Remove a Roll PinThrough-hole removal is straightforward. Blind-hole removal is where problems arise — and where the wrong approach damages the hole, the component, or both.Through-Hole RemovalPosition the roll pin punch — nub on the rim — and drive steadily from one side. If the pin is seized from corrosion, apply penetrating oil, wait at least 15 minutes, and try again before applying more force. Forcing a corroded pin without penetrant risks distorting the bore.Blind Hole Removal — Four MethodsA blind hole does not pass all the way through the component. The pin goes in from one side only. Standard punch-through removal is not possible. These are the four methods that work:Method 1: Grease HydraulicPack the hollow bore of the pin completely full of thick grease — no air gaps. Find a punch that is a close fit to the inside bore diameter. Drive the punch firmly into the grease-filled bore. The incompressible grease transmits hydraulic force to the closed end of the pin and presses it back out of the hole. This is the cleanest method when the bore is accessible. A well-fitting punch is essential — a loose punch just displaces the grease without building pressure.Method 2: Tap MethodRun a tap of appropriate size into the hollow bore to cut threads into the bore wall. Thread a bolt or stud into the tapped bore, then pull with a slide hammer or bearing puller. Do not over-torque the tap — spring steel is hard, and the goal is to thread the bore wall, not break the tap.Method 3: Self-Tapping ScrewDrive a self-tapping screw into the hollow bore until it bites firmly. Use the screw head as the extraction grip point — lever against the surrounding surface or attach a slide hammer. Best for larger pin sizes (6 mm and above) where the bore is wide enough to accept a useful self-tapping screw.Method 4: Heat Annealing Heat the area around the pin to approximately 400–500°C — a dull red on the steel surface. The heat anneals the spring steel, relaxing the temper and eliminating the radial interference force. Once cooled, the pin can be removed with minimal force. Caveats: this permanently destroys the pin. Never use heat near seals, O-rings, flammable fluids, or lubricants. Use appropriate PPE — heat-resistant gloves, safety glasses, face shield.Common MistakesThese four mistakes account for the overwhelming majority of roll pin installation and removal failures encountered in Australian maintenance workshops.1. Wrong Punch — Expanding the Pin in the BoreThe most common and most costly roll pin mistake. A flat punch or a punch smaller than the pin OD enters the hollow bore on contact. Every hammer blow then expands the pin walls outward. The more you drive, the more firmly the pin locks in place. The pin generally cannot be driven out at this point — it needs to be drilled out, which risks the bore. Fix: use a dedicated roll pin punch with a nub that seats on the outer rim.2. Drilling the Hole OversizedIf the hole is drilled oversize — even half a millimetre in smaller pin sizes — the pin will not develop enough spring force to create a reliable interference fit. The pin vibrates free, walks under cyclic loading, or fails to transmit torque. If the pin slides in by hand without resistance, the hole is too big. Remedies: use the next pin size up, bush and re-drill, or redesign the joint.3. Wrong Slot Orientation on High-Load ApplicationsFor slotted pins in torque-transmitting or vibration-prone applications, the slot must be perpendicular to the primary load direction. Ignoring this on a gearbox shaft or drivetrain pin can halve service life. Where correct slot orientation is difficult to guarantee, switch to coiled spring pins.4. Using a Roll Pin as a Shear PinA common and damaging mistake in agricultural and outdoor power equipment. A shear pin is soft and designed to break cleanly under overload, protecting the drivetrain. A roll pin is spring steel — engineered not to fail. If substituted for a shear pin on a PTO drive, auger, or mower deck, the roll pin will not break when the system overloads. The force travels into the gearbox and driven components instead, causing far more damage. Always replace shear pins with the correct specified material.Common ApplicationsRoll pins appear across a wide range of mechanical assemblies in Australian industry, agriculture, and engineering maintenance.Gear and Sprocket Retention on ShaftsThe most common application. The pin passes through aligned holes in the shaft and hub, locking the gear, sprocket, or pulley so it rotates with the shaft. For light to medium duty torque transmission this is simple, economical, and reliable. For high torque or precision gearboxes, a key and keyway is more appropriate — follow the original design specification.Pivot Pins and Hinge PinsRoll pins create pivot points in mechanical linkages, agricultural implement joints, loader arms, and manually operated mechanisms. The interference fit keeps the pin from walking out longitudinally under cyclic loading without any secondary retention hardware.Handle and Lever RetentionTool handles, valve handles, and lever mechanisms are commonly retained by a single roll pin through the handle socket and the shaft or stem. Quick to install, easy to replace when a handle is damaged.Agricultural MachineryRoll pins appear throughout tractors, planting equipment, harvesters, spreaders, and three-point linkage implements. They are a standard maintenance consumable on Australian farms. Remember: they are not interchangeable with shear pins on PTO drives and cutting mechanisms.Automotive and Vehicle MaintenanceGearshift linkages, brake linkages, steering columns, and door latch mechanisms commonly use roll pins. Always match the original OEM diameter and material when replacing in automotive applications.General Engineering MaintenanceFor maintenance teams, roll pins are a standard consumable. Keeping an assortment of common metric sizes on the shelf — 2 mm through 8 mm in typical lengths — covers the majority of routine replacement tasks without sourcing individual sizes on short notice.Roll Pin vs Dowel Pin vs Cotter Pin vs Shear PinPin fasteners cover a range of designs and purposes. Here is how roll pins compare with the three other pin types most commonly encountered in Australian maintenance and engineering work. Feature Roll Pin (Spring Pin) Dowel Pin Cotter / Split Pin Shear Pin Function Lock component to shaft; interference-fit retention Precision alignment of mating components Secondary locking — prevents nut or pin backing out Controlled failure — overload protection Material Spring steel (1070), stainless 420, alloy Hardened alloy steel, stainless; precision-ground Mild steel, brass, stainless Soft brass, Grade 2 steel, proprietary alloy Hole requirement Standard drilled hole — nominal diameter, H13/H14 Precision-reamed hole — H7 (tight fit) Drilled hole — loose tolerance acceptable Drilled to OEM specification Vibration resistance Excellent — self-retaining interference fit Good in static assembly; needs secondary retention dynamically Good — bent legs prevent back-out N/A — designed to fail under overload Reusable? Slotted: inspect before reuse. Coiled: yes (same hole) Yes, with care No — always replace after removal No — replace after shear When to use Lock gear/hub to shaft; pivot; hinge; quick assembly Precision alignment in static assembly Lock castle nut; retain clevis or axle pin PTO shaft; auger drive; snowblower impeller The practical rule: use a roll pin to lock a component to a shaft where precision location is not required. Use a dowel pin where precision alignment in a static joint is required (and ream the hole to H7). Use a split/cotter pin as secondary retention on a nut, clevis pin, or axle. Use the correct specified shear pin — never a roll pin — where the fastener must break under overload.See the Split Pin and Cotter Pin Guide and the Clevis Pin Guide for detail on those fastener types. For fastener metric sizing context, see the Metric vs Imperial Fasteners Guide.AIMS Industrial Spring Pin RangeAIMS Industrial stocks metric slotted spring pins (DIN 1481) in carbon steel and stainless steel, covering sizes 2 mm through 8 mm in the most common lengths. All sizes are sold individually or in bulk packs to suit workshop stock requirements.For maintenance teams who need a broad size range without ordering individually, the Champion CA1715 Spring Pin Assortment Kit is a practical solution: 18 metric sizes from 2 mm to 6 mm, 360 pieces total, in a labelled assortment case. It covers the majority of routine replacement sizes in a single purchase.View the full AIMS spring pin range. If you need a size, material, or quantity not listed online, get in touch — we can source to order.Frequently Asked QuestionsWhat is a roll pin?A roll pin is a hollow spring steel cylinder with a single longitudinal slot along its length. It is manufactured slightly oversized relative to the hole it fits. When driven in, the slot closes under compression and the pin springs against the hole wall, creating an interference fit that retains the pin without threads or adhesive. Roll pins are used to lock components such as gears, pulleys, and levers to shafts, and as pivot and hinge pins in mechanical assemblies.What is the difference between a roll pin and a spring pin?There is no functional difference — they are the same product. "Roll pin" describes how it is made (a sheet of spring steel rolled into a cylinder). "Spring pin" is the broader engineering term that appears in DIN 1481 and ISO 8752. Both names refer to the same slotted, hollow, spring-steel cylinder. The potential for confusion is that "spring pin" technically also covers coiled spring pins, which are a distinct product — so when precision matters, specify "slotted spring pin" or "roll pin" to be unambiguous.What is a sellock pin or selock pin?A sellock pin (also spelled selock or sel-lok) is the Australian and UK trade name for a standard roll pin or slotted spring pin. The term originated as a brand name and became genericised in the Australian fastener trade — the same way "Biro" became the common word for a ballpoint pen. If a tradesperson asks for a sellock pin, they want a standard metric DIN 1481 slotted spring pin. Blackwoods, United Fasteners, and Cost Less Bolts all stock them under this name. Same product, different label.What is a tension pin?A tension pin is another name for a slotted spring pin (roll pin), used mainly in North American industrial literature and in specifications following ASME B18.8.2. The name refers to the working principle: the compressed pin exerts radial tension against the hole wall. In Australian usage, "roll pin" and "sellock pin" are more common terms for the same product.What is the difference between a slotted spring pin and a coiled spring pin?A slotted spring pin (roll pin) is made from a single sheet of spring steel rolled into a C-shape with one slot. A coiled spring pin is made from a strip of spring steel coiled approximately 2.25 turns, giving a multi-layer cross-section. Coiled pins have better fatigue resistance, absorb vibration and shock more effectively, require no slot orientation during installation, and can be reused in the same hole. They cost more. For most standard maintenance applications, slotted pins are sufficient. For high-vibration, high-cycle, or shock-load applications, coiled pins are the better choice.What size hole do you drill for a roll pin?Drill the hole to the nominal pin diameter. For a 5 mm roll pin, drill a 5 mm hole. Roll pins are manufactured oversize and compress on entry to create the interference fit. No reaming is required. If the pin slides in by hand without any resistance, the hole is too large — use the next size up or bush and re-drill.How do you install a roll pin correctly?Drill to nominal diameter, align the components, and present the pin chamfered end first. Use a dedicated roll pin punch — it has a nub on the face that seats on the rim of the hollow pin, preventing the punch from entering the bore and expanding the walls. Drive with steady progressive blows to flush or slightly below the surface. For slotted pins, orient the slot perpendicular to the primary load direction before driving. Do not use a standard flat punch — it will enter the bore and seize the pin.Which way should the slot face when installing a roll pin?Orient the slot perpendicular to the primary load direction. For a shaft-to-hub connection (gear, pulley, or sprocket on a shaft), orient the slot so it faces toward and away from the shaft axis — not along it. Incorrect slot orientation can reduce service life by up to 50% in high-load or high-cycle applications. Coiled spring pins require no orientation — they perform identically regardless of rotational position.What happens if you use the wrong punch size on a roll pin?If you use a flat punch or a punch that is smaller than the pin OD, it enters the hollow bore of the pin rather than bearing on the rim. Every hammer blow then expands the pin walls outward against the hole. The more you drive, the more firmly the pin locks itself in place — at this point it generally needs to be drilled out, which risks damaging the bore. Always use a dedicated roll pin punch with a nub that seats on the outer rim of the pin.How do you remove a roll pin from a blind hole?Four methods work for blind holes: (1) Grease hydraulic — pack the hollow bore completely with grease, use a close-fitting punch to drive into the bore, and hydraulic pressure forces the pin out. (2) Tap method — run a tap into the bore to cut threads, thread in a bolt, and pull with a slide hammer or bearing puller. (3) Self-tapping screw — drive a self-tapper into the bore and lever against the surface. (4) Heat annealing — heat to dull red (~400–500°C) to relax the spring temper; the pin can then be removed with minimal force. Note: heat permanently destroys the pin and must not be used near seals or flammable materials.Can you reuse a roll pin?Coiled spring pins can be reused in the same hole because their spring-back is consistent and they do not typically flare or deform on removal. Slotted spring pins can theoretically be reused if undamaged — inspect for flaring at the ends, cracking at slot corners, or deformation of the bore. In practice, slotted pins are inexpensive enough that replacement is standard practice. Never reuse a slotted pin removed from a corroded or oversized hole.Can I use a roll pin as a shear pin?No. A shear pin is a deliberately weak component — made from soft brass, Grade 2 steel, or a specific alloy — designed to break cleanly under overload, protecting the gearbox and driven components. A roll pin is spring steel: tough, hard, and engineered not to fail. Substituting a roll pin for a shear pin on a PTO drive, auger, or mower deck means the pin will not break when the drivetrain overloads. The force travels into the gearbox and downstream components instead, causing far more expensive damage. Always replace shear pins with the correct specified material.What is the difference between a roll pin and a dowel pin?A roll pin is a hollow, slotted spring steel cylinder that fits a standard drilled hole (H13/H14 tolerance) and retains itself by interference fit. A dowel pin is a solid, precision-ground cylinder that requires a reamed H7 hole and is used for precision alignment of mating components in static assemblies. Roll pins tolerate loose hole tolerances and resist vibration well. Dowel pins require precision reaming and are used where dimensional repeatability is critical — engine blocks, jig fixtures, precision machinery. The two are not interchangeable in precision-alignment applications.What material should I choose for a roll pin?Carbon spring steel zinc-plated is the standard choice for indoor or dry industrial applications. Stainless steel Grade 420 is required for corrosion-prone environments: food processing, marine, outdoor machinery, and wet-process plant. Alloy steel suits very high shear or shock-load applications where spring steel performance is insufficient. For standard maintenance applications, carbon steel zinc-plated is the correct default.What roll pins does AIMS Industrial stock?AIMS Industrial stocks metric slotted spring pins (DIN 1481) in carbon steel and stainless steel, in sizes 2 mm to 8 mm across the most common lengths. The Champion CA1715 assortment kit (18 sizes, 2–6 mm, 360 pieces) is also available. View the full range at aimsindustrial.com.au/fasteners/pins/spring-pins/, or contact the team for sizes or quantities not listed. Our Tap Types guide covers every cutting and forming tap variant with material-specific selection rules. For pop-rivet guns and nutsert tools, browse the AIMS rivet tools collection. Need roll groove fittings? Browse the AIMS range at roll groove fittings.
Read moreThreaded Rod Guide: All Thread, Grades & Sizes
Need another reference chart? Browse the full AIMS Engineering Reference Charts library — drill bit sizes, tap drill, torque, viscosity, GD&T, AS/NZS standards and more. What Is Threaded Rod? Threaded rod is a length of metal bar stock threaded continuously along its full length, from one end to the other. Unlike a bolt, which has a formed head and a specific shank length, threaded rod has no head — it's just thread, all the way through. That makes it endlessly adjustable: you can cut it to any length, run nuts and fittings anywhere along it, and use it for applications a standard bolt simply can't reach. Threaded rod follows the same metric thread pitch standards as bolts — for the full M3 through M24 reference covering pitch, diameter and head sizes, see the AIMS Metric Bolt Size Guide. In the trade, threaded rod gets called a lot of different things. If someone asks you for allthread, stud rod, studding, Booker rod, hanger rod, or threaded bar — they're all talking about the same product. The terminology varies by industry, region, and how long the person has been in the game. We'll cover all the names below. AIMS Industrial supplies threaded rod in a full range of grades, materials, and metric sizes — from M6 through to M36 in stock, with larger sizes and cut lengths available to order. If you need a specific grade or finish that isn't showing online, get in touch. All the Names for Threaded Rod This is one of those products that has accumulated more names than almost anything else in the fastener world. Here's the full list, and when you'll hear each one: Threaded Rod The universal standard term. Used by engineers, designers, and fastener suppliers worldwide. If you're specifying on a drawing or purchase order, this is what to write. All Thread / Allthread / ATR Short for all-thread rod — meaning threaded from end to end, as opposed to a stud bolt that has a plain shank in the middle. ATR is the written abbreviation you'll see on supplier datasheets. "Allthread" is common in the electrical, plumbing, and HVAC trades across Australia. Threaded Bar Common in the construction and civil trades, particularly for concrete anchor applications. "Threaded bar" often implies a longer length — 1 m or 2 m stock — rather than a short fastener. Studding The UK trade term, and still used in Australia by plumbers, electricians, and building services contractors. "A length of studding" means a section of fully threaded rod cut to suit the job. Stud Rod Common in the mechanical, electrical, and plumbing (MEP) sector. Often used alongside strut channel systems (Unistrut, OzStrut, EzyStrut) for suspending pipework, cable tray, and HVAC ducting from structural steel or concrete soffits. Hanger Rod The HVAC and fire protection term. When contractors hang duct, air handling units, or sprinkler pipework from a slab, they do it with hanger rods — typically M10 or M12 galvanised, fixed with a concrete anchor above and a clevis hanger or rod hanger bracket below. Anchor Rod The civil and structural term. Anchor rod is threaded bar chemically set (epoxied) into core-drilled holes in concrete — used for base plates, handrails, structural connections, and post-installed anchors. Typically specified as Grade 8.8 or stainless, not Grade 4.6. Booker Rod (Australian Trade Term) If you're in the Australian building and construction trade, you'll hear "Booker rod" used interchangeably with threaded rod or allthread. It's a fully genericised trade term — like "Biro" for a ballpoint pen or "Crescent spanner" for an adjustable wrench — where a brand name has become the common name for the product category. The name is most likely derived from Booker Bros, a major Australian building materials distributor that was widespread in the mid-20th century. You'll also see it spelled "Brooker rod" — that's the same thing, different spelling. Both circulate in the trade. If a sparky or plumber asks for Booker rod, hand them M12 HDG allthread and you'll be right. Ready Rod / Redi-Rod North American trade terms that occasionally appear in Australian catalogues and online searches. Same product — fully threaded rod, typically zinc-plated or HDG, sold in 1 m or 3 m lengths. Coil Rod / Coil Thread Rod A specific variant with a different thread profile — round crests rather than the standard V-form. Coil rod is used in formwork tie systems, rebar tying, and some proprietary concrete accessories. It is not interchangeable with standard metric threaded rod. What Is Threaded Rod Used For? Threaded rod is one of those products that appears on virtually every commercial building site and in most industrial maintenance workshops. The common thread across all applications is the same: you need something suspended, anchored, braced, or clamped at a precise position, using a fastener you can adjust and cut to length. Here's how each trade uses it. HVAC Suspending rectangular and circular ductwork from concrete soffits or structural steel. Fan coil units, air handling units (AHUs), and duct runs are hung on M10 or M12 HDG rod, passed through a concrete anchor above and terminated with a nut and vibration isolator below. For heavier AHUs and mechanical plant, M16 high-tensile rod is standard. Plumbing Pipe hangers for copper, stainless, PVC, and press-fit pipework. Threaded rod sets the drop from structural steel or slab to the pipe hanger bracket, allowing fine height adjustment with two nuts. M10 is the workhorse size for commercial plumbing hangers; M8 suits light-duty residential. Electrical Cable tray support, conduit runs, and switchboard base frames. Electrical contractors buy large quantities of M10 zinc-plated or HDG rod for supporting cable management systems throughout commercial fitouts and industrial switchrooms. Fire Protection Sprinkler pipe hangers to AS 1530. Fire contractors use HDG or stainless rod for sprinkler hangers and brace rods, with strict requirements on spacing, rod diameter, and anchor type. M12 HDG is typical for standard commercial sprinkler installations. Construction and Civil Post-installed anchor bolts: M16 or M20 Grade 8.8 rod is chemically set into core-drilled holes in concrete using two-component epoxy (Loctite 5088, Ramset HIT-RE 500 V4, or similar) for base plates, guardrail posts, mezzanine columns, and structural connections. Concrete formwork uses proprietary coil rod (not standard allthread) to tie form faces. Workshop and Industrial Maintenance Machinery bases and levelling feet, press frames, jig and fixture construction, custom clamps, structural shelf uprights, and industrial workbench legs. M12 is the most common size for workshop use — strong enough for most loads, easy to cut with a hacksaw, and compatible with standard hex nuts and coupling nuts. DIY and Furniture Industrial-style furniture — bookcase uprights, table legs, shelving systems — using M10 or M12 rod with washers and hex nuts as exposed fasteners. It's a popular look in commercial fitouts and home workshops, and threaded rod is cheap, strong, and adjustable. CNC and Hobby Machining (Acme Thread) When people search for threaded rod for CNC leadscrews, lathe repairs, or workbench vise screws, they typically need acme thread rod — not standard V-thread allthread. See the Acme Thread section below. Grades and Strength Classes Not all threaded rod is the same strength. Getting the grade wrong on a structural anchor or load-bearing hanger rod is a genuine safety issue — so this matters. Grade 4.6 — Mild Steel (General Purpose) The workhorse grade. Grade 4.6 has a minimum tensile strength of 400 MPa and a yield strength of 240 MPa. It's suitable for general construction, MEP suspension, light structural work, and most non-safety-critical applications. When someone says "standard allthread" in Australia, they usually mean Grade 4.6 galvanised. Manufactured to DIN 976 / AS 2451. Available in zinc-plated, hot-dip galvanised (HDG), and plain (bare steel) finishes. Grade 8.8 — High Tensile For structural anchors, high-load assemblies, and applications where you need significantly more clamping force or tensile capacity. Grade 8.8 has a minimum tensile strength of 800 MPa and a yield strength of 640 MPa — more than double Grade 4.6. When a structural engineer specifies "high tensile rod" for an anchor bolt or moment connection, they mean 8.8. Tightening threaded rod to the correct clamping force uses the same torque values as a bolt of the same grade and diameter — see the AIMS Metric Bolt Torque Chart or, for imperial/SAE rod, the Imperial/SAE Bolt Torque Chart. Do not substitute 4.6 for 8.8 in structural applications. The strength difference is material. Manufactured to DIN 976 / AS 3501. Available in zinc-plated and HDG. Stainless Steel — Grade A2 (304) and A4 (316) For corrosion-resistance where galvanising isn't adequate. Grade 304 (A2) handles most industrial and general outdoor environments well. Grade 316 (A4) adds molybdenum, which significantly increases resistance to chlorides — it's the grade to specify for coastal, marine, food processing, pharmaceutical, and chemical plant environments. Stainless rod is slightly lower in tensile strength than Grade 8.8 — 304 runs around 500 MPa UTS, 316 slightly less — but far outperforms galvanised in corrosive environments over time. Brass For electrical applications requiring non-magnetism, light corrosion resistance, or aesthetic finish. Brass rod is used in marine fittings, electrical panel grounding studs, and decorative furniture. Not for structural use. Nylon For electrical isolation, chemical resistance, and applications where a fastener must be non-conductive. Used in circuit boards, chemical plant, and food-grade equipment. Significantly lower strength than steel — not structural. Grade Comparison Table Grade Material Min Tensile (MPa) Min Yield (MPa) Typical Finish Best For 4.6 Mild steel 400 240 Zinc plate, HDG General construction, MEP hangers 8.8 High tensile steel 800 640 Zinc plate, HDG Structural anchors, high-load A2 / 304 Stainless steel ~500 ~210 Brushed/natural General corrosion resistance A4 / 316 Stainless steel ~500 ~210 Brushed/natural Marine, coastal, food, chemical Brass Brass alloy ~380 — Natural Electrical, decorative Nylon Polyamide ~80 — Natural Electrical isolation, chemical Finishes — Zinc Plated vs Galvanised vs Stainless Even within Grade 4.6, the finish you choose makes a significant difference to how long the rod will last in the environment it's going into. Plain / Bare Steel No coating. Cheapest option. Suitable only for dry, indoor, protected environments — it will rust quickly in any moisture. Typically used in shop settings or as a temporary fastener. Zinc Plated (Electro-Galvanised) A thin electroplated zinc layer — typically 5–12 µm. Good for dry to mildly damp indoor environments. Standard for most light commercial and residential fitout work. Not suitable for outdoor or humid environments over the long term. Hot-Dip Galvanised (HDG) Zinc coating applied by immersion in molten zinc — typically 45–85 µm, much thicker than electroplated. Provides good long-term corrosion protection for outdoor and semi-exposed environments. This is the standard spec for commercial construction, HVAC, plumbing hangers, and most outdoor structural applications in Australia. The coating adds a small amount of bulk to the thread — use an appropriate nut that accommodates HDG rod, or the fit will be tight. Stainless Steel 304 No separate coating — the alloy itself provides corrosion resistance through a chromium oxide passive layer. Suitable for general outdoor, marine proximity, wet areas, and mild chemical exposure. Doesn't require ongoing maintenance. Preferred for food-grade and pharmaceutical applications. Stainless Steel 316 The marine-grade option. Molybdenum content (2–3%) provides meaningfully better chloride resistance than 304. Specify 316 for anything within a few kilometres of the coast, anything submerged or regularly wet in salt water, or any chemical/food processing application involving chlorine compounds. The price premium over 304 is significant — use it where it's genuinely needed, not as a blanket upgrade. Metric Sizes and Standard Lengths In Australia, threaded rod is sold in metric coarse thread as the standard. Metric fine thread is available but rarely stocked — it's a special order item for most suppliers. Most Common Sizes in Trade Use If you're buying threaded rod for MEP, construction, or workshop use, these four diameters cover the vast majority of applications: M8 — Light-duty hangers, residential plumbing, light cable tray, furniture M10 — Commercial plumbing hangers, medium cable tray, electrical conduit supports M12 — HVAC duct hangers, structural bracing, workshop and machinery applications M16 — Heavy HVAC plant, AHUs, structural base plates, heavy-duty anchor rods Full Metric Range Standard stock sizes typically run from M6 through to M30 or M36. Larger sizes — M39, M42, M48, M52, M56, M64 — are available but are usually special order from fastener specialists. The full metric coarse range is: M3, M4, M5, M6, M8, M10, M12, M14, M16, M18, M20, M22, M24, M27, M30, M33, M36, M39, M42, M48, M52, M56, M64. Standard Lengths Most suppliers stock threaded rod in 1 m and 3 m lengths. Some suppliers offer 2 m stock. Cut-to-length is available from most fastener specialists — useful when you need a precise length and want to avoid site waste. Size and Load Guide Diameter Pitch (coarse) Tensile Stress Area (mm²) Indicative SWL Grade 4.6 (kN) Common Use M8 1.25 mm 36.6 ~6.2 Light hangers, furniture M10 1.50 mm 58.0 ~9.8 Plumbing, cable tray M12 1.75 mm 84.3 ~14.3 HVAC, workshop, general construction M16 2.00 mm 157 ~26.7 Heavy plant, structural anchors M20 2.50 mm 245 ~41.7 Heavy structural, base plates M24 3.00 mm 353 ~60.0 Large structural connections SWL values are indicative for Grade 4.6 rod in axial tension. Always consult a structural engineer for load-critical applications. Grade 8.8 values are approximately 2.7× higher at the same diameter. How to Cut Threaded Rod Cutting threaded rod is straightforward, but the method matters — a badly cut end with a crushed or burred thread makes it frustrating to run a nut on, and a thread that's too short means the nut won't develop full engagement. Here's how to do it cleanly. The Nut Trick (Recommended) This is the trade-standard method for getting a clean thread end every time: Thread two nuts onto the rod and run them past the intended cut point. Jam the two nuts against each other by turning them in opposite directions — this locks them in place. Slide the locked pair back to your cut mark. The nut face nearest the cut gives you a straight guide for your saw blade. Cut through the rod using a hacksaw or angle grinder, using the nut face as a guide to keep the cut square. After cutting, back the two nuts off past the cut end — as they unwind over the fresh cut, they reform and clean up any minor burring on the thread. The result is a clean, usable thread end with minimal fuss. It's the same trick used by every experienced sparky, plumber, and rigger in the country. Tool Options Hacksaw: Ideal for one-off cuts, softer materials (brass, stainless up to M16), or when you need a quiet, spark-free method. Clamp the rod in a vise for a straight cut. Use a bi-metal blade with 18–24 TPI for steel. See the hacksaw blade guide for TPI selection. Angle grinder (cutting disc): Fast for volume cutting and larger diameters. Leaves a burr that needs cleaning — use the nut trick, or dress the end with a bench grinder. See the cutting disc guide for disc selection. Metal chop saw: Best for workshop settings cutting multiple lengths. Gives a clean square cut. Use a metal-rated abrasive disc or cold saw blade. Reciprocating saw: Workable in tight spaces on site. Use a metal-rated bi-metal blade. Not as clean as a hacksaw or chop saw. Bolt cutters: Don't. They crush the thread end and make it unusable without re-tapping or grinding. After Cutting Always run a nut over the cut end before putting the rod into service. If the nut won't pass smoothly, dress the end with a fine file, bench grinder, or thread die to remove any remaining burr. How to Join Threaded Rod (Coupling Nuts) When you need to extend a length of threaded rod — to reach from a slab anchor to a low duct, or to join two cut lengths — the tool for the job is a coupling nut. It's also called an extension nut, long nut, rod joiner, or barrel nut. A coupling nut is a hex nut machined to a much longer length than a standard nut — typically 3× to 5× the diameter. Both ends are fully threaded to the same pitch as the rod, so you simply thread one rod end in from each side and tighten with two spanners, jamming the rods against each other inside the nut. For clean connections: Make sure both cut ends are clean and deburred before threading into the coupling nut. Achieve full thread engagement — the rod end should bottom out at or past the centreline of the nut. Use two spanners to tighten — hold the nut body, turn the rod. Don't trust finger-tight joints under load. For vibration environments, apply a thread-locking compound such as Loctite 222 (low-strength, removable) to the rod thread before assembly. Reducer coupling nuts are available for joining two different diameters — for example, M12 on one end and M10 on the other. These are useful when transitioning between a structural anchor rod (M16) and a lighter hanger rod (M12). Acme Thread — When Standard Allthread Won't Do If you're searching for threaded rod for a CNC leadscrew, lathe repair, workbench vise, or scissor jack — standard metric allthread is the wrong product. What you need is acme thread rod. What Is Acme Thread? Acme thread is a trapezoidal thread form — the thread profile is a trapezoid rather than the V-shape of standard metric threads. The flank angle is 29° (compared to 60° for metric V-threads). The Australian/international equivalent is ISO trapezoidal thread (30° flank angle), which is functionally very similar and often used interchangeably in practice. Why Acme Thread, Not Standard Allthread? Standard V-thread (metric coarse) is designed for fastening — clamping two things together. It has a steep thread form that grips well under static load but has high friction when rotated under load, generates heat, and wears relatively quickly if used as a power-transmission screw. Acme thread is designed for movement — converting rotation into controlled linear motion. The wider, flatter tooth profile: Reduces friction under load compared to V-thread Handles higher axial loads with less thread wear Self-cleans in dusty or debris-laden environments Supports multi-start thread configurations (2-start, 4-start) for faster linear travel per revolution Where Acme Thread Is Used CNC router and mill leadscrews Lathe cross-slide and carriage screws Woodworking face vice and leg vice screws Scissor lifts and mechanical jacks Gate and valve actuator stems Linear actuators and positioning stages Sourcing Acme Thread Rod in Australia Standard metric allthread is stocked everywhere. Acme thread rod is considerably harder to find — most hardware stores and general fastener suppliers don't carry it. For AU sourcing, contact AIMS Industrial or specialist fastener suppliers. Multi-start acme rod (2-start, 4-start) is a special order item — allow lead time. Threaded Rod vs Bolts — When to Use Each Threaded rod and bolts solve different problems. Here's a quick guide to when each makes sense: Situation Use Threaded Rod Use a Bolt Length needed exceeds standard bolt sizes ✓ Position of nut needs to be adjustable along the fastener ✓ Suspending from above (hanger application) ✓ Connecting two surfaces without a head clearance ✓ Chemical anchor / epoxy set into concrete ✓ Standard through-bolt, flange bolt, or machine fastening ✓ Quick assembly where head clearance exists ✓ Tightening with a single tool from one side ✓ Buying Guide — What to Specify When ordering threaded rod, specify these four things and you'll get the right product every time: Diameter: M8, M10, M12, M16, M20 etc. Grade: 4.6 (general), 8.8 (structural/high load), A2-304 (corrosion resistance), A4-316 (marine/coastal) Finish: Zinc plated (dry indoor), HDG (outdoor/construction), Stainless (corrosive environments) Length: 1 m, 2 m, 3 m stock, or cut to length If you're not sure which grade or finish suits your application, contact the AIMS team with a description of the environment and load — we'll point you in the right direction. Browse the AIMS Industrial allthread range, including Grade 4.6 galvanised, Grade 8.8 high tensile, and stainless steel threaded rod. Accessories and Hardware for Threaded Rod Threaded rod rarely works alone — it's part of a system. Here's the hardware you'll need alongside it, and when each piece is used. Hex Nuts The standard nut for threaded rod. Use two hex nuts per connection point — one to locate the fitting or bracket, one as a jam nut to lock the first in place and prevent it from working loose under vibration or load. For HDG rod, use HDG nuts (the zinc coating slightly increases the rod's effective diameter — standard zinc-plated nuts will be tight). Match grade: use Grade 4 or 5 nuts on Grade 4.6 rod; use Grade 8 nuts on Grade 8.8 rod. Nyloc Nuts (Nylon Insert Lock Nuts) A nylon insert in the top of the nut grips the thread and resists loosening under vibration — without needing a second jam nut. Ideal for dynamic or vibrating applications: HVAC fans, machinery mounts, motor bases. Nyloc nuts are single-use by design — the nylon compresses on first use. Don't re-use a nyloc nut that's already been run down a thread. See the metric-vs-imperial fasteners reference guide if there's no concrete soffit above. A range of clamp sizes suits different beam flange thicknesses. Most accept M10 or M12 rod directly through a threaded eye or clevis hole. Concrete Anchors and Wedge Anchors For attaching hanger rod to concrete soffits, mechanical wedge anchors or chemical anchor systems are used. Wedge anchors (also called expansion anchors) are fast to install — drill hole, insert anchor, tighten nut. Chemical anchors (epoxy anchors) give higher loads and work in cracked concrete or close to edges where expansion anchors fail. The threaded rod is either part of the wedge anchor assembly, or is set separately into a chemical anchor system. For structural applications, specify the anchor to the concrete strength and required load — don't guess. Installation Tips and Common Mistakes Most threaded rod installation problems are simple to avoid if you know what to watch for. Here are the common ones. Not Using a Jam Nut A single nut run onto threaded rod will loosen under vibration over time. Always use two nuts at each connection point, or a Nyloc nut. Thread the first nut to position, then wind the second nut down against it and hold the first nut with one spanner while tightening the second with another. This locks the pair — they can't turn independently. The two-nut method is faster and cheaper than discovering a dropped duct fitting six months later. Using Grade 4.6 Where 8.8 Is Specified Grade 4.6 is fine for MEP hangers, shelf uprights, and general non-structural work. It is not a substitute for Grade 8.8 where an engineer or standard has specified high tensile rod — in anchor bolts, structural connections, or load-rated hanger systems. The strength difference is more than 2:1. If the spec says 8.8, use 8.8. Wrong Nut for HDG Rod Hot-dip galvanised rod has a thicker, more irregular thread surface than zinc-plated rod. Standard zinc-plated nuts can bind — or the threads can strip — if forced onto HDG rod. Use HDG nuts (or specify "HDG oversize") with HDG rod. They're tapped slightly larger to account for the coating. The fitting should still be firm, not sloppy — if it's too loose, you have a mismatch. Insufficient Thread Engagement A nut needs adequate thread engagement to develop its full rated load. The rule of thumb: minimum thread engagement equals the nominal diameter — so an M12 nut needs at least 12 mm of rod engagement, and preferably more. On a coupling nut joint, make sure each rod end runs at least to the centreline of the coupling nut. Short engagement is one of the most common causes of nut strip-out under load. Burred or Damaged Thread End A cut or knocked thread end that hasn't been cleaned up will cause a nut to jam partway, which either cross-threads the nut or causes you to strip it while trying to force it. Clean every cut end before assembly. Run a nut over it first — if it catches, use a thread file, die, or the nut trick to clean it before it becomes your problem inside a hanger assembly in the ceiling. Mixing Metric and Imperial Thread Metric and imperial (UNC/UNF) threaded rod look almost identical to the naked eye, and you will occasionally get both on site. A metric nut will not fit an imperial rod and vice versa — forcing it strips both. When you're unsure, use a thread gauge, or count the threads per 25 mm against a known pitch chart. The most common confusion is M12 (1.75 mm pitch) vs 1/2" UNC (12.7 TPI / 2.0 mm pitch) — similar diameter, different pitch. Ignoring Corrosion Requirements Zinc-plated rod installed outdoors, in roof spaces, near the coast, or in humid environments will rust within months. The corrosion spreads from the cut ends first — zinc plating is damaged when the rod is cut, and the bare steel underneath is immediately exposed. Either use HDG or stainless, or apply cold galvanising compound to cut ends at minimum. For coastal or marine applications, 316 stainless is the only acceptable long-term solution. Standards and Compliance For most trade and construction applications in Australia, the relevant standards for threaded rod are: AS 2451 — Metric hex nuts, including those used with threaded rod. Sets dimensional and mechanical requirements. AS 3501 — Metric bolts, screws, and studs, including high-tensile threaded rod specifications. DIN 975 / DIN 976 — German industry standards widely referenced by Australian fastener suppliers for threaded rod dimensions, thread pitch, and mechanical properties. Most Australian threaded rod is manufactured to DIN 976 specifications. AS 3569 — Not directly for threaded rod, but relevant when threaded rod is used in wire rope or rigging assemblies. National Construction Code (NCC) / Building Code of Australia (BCA) — Sets requirements for fastener grades in structural applications. Where threaded rod is used as a structural element, NCC compliance requires it to be specified and installed to the relevant structural engineering standard. For any application where threaded rod forms part of a structural connection, load-rated hanger system, or fire protection assembly — get the engineering right. Threaded rod is cheap; engineering failures are not. Frequently Asked Questions What is the difference between threaded rod, allthread, and studding? They're all the same product — a length of metal bar stock threaded along its full length with no unthreaded shank or head. Threaded rod is the standard engineering term. Allthread (or all thread rod / ATR) is the common trade abbreviation. Studding is the UK trade term widely used in Australian plumbing and electrical work. All three mean fully threaded bar — the name varies by trade and region, not by product. What is Booker rod? Is it the same as Brooker rod? Yes — Booker rod and Brooker rod are the same thing, just two spellings of the same Australian trade term. Both refer to standard fully threaded rod (allthread). The term is believed to derive from Booker Bros, a major Australian building materials distributor, whose branded threaded rod became so ubiquitous that the name stuck as the generic trade term for the product — similar to how 'Biro' became the word for a ballpoint pen. If someone asks for Booker or Brooker rod, give them standard galvanised allthread in the diameter they need. What is the difference between Grade 4.6 and Grade 8.8 threaded rod? Grade refers to strength. Grade 4.6 is mild steel with a minimum tensile strength of 400 MPa — suitable for general construction, MEP hangers, and non-structural fastening. Grade 8.8 is high tensile steel with a minimum tensile strength of 800 MPa — more than double the strength of 4.6 — and is specified for structural anchor bolts, high-load clamping, and any application where failure would have safety consequences. Do not substitute Grade 4.6 for Grade 8.8 in structural or load-rated applications. Should I use galvanised or stainless threaded rod outdoors? It depends on the environment. Hot-dip galvanised (HDG) rod is adequate for most Australian outdoor construction environments — exposed but not directly coastal. For coastal locations (within a few kilometres of the ocean), food processing, pharmaceutical plants, or chemical environments involving chlorides, specify stainless steel Grade 316 (A4). Grade 304 stainless is a good middle ground for general corrosion resistance without the cost of 316. For dry, protected indoor environments, zinc-plated rod is sufficient. What size threaded rod do I need for pipe hangers? M10 is the standard size for most commercial plumbing pipe hangers — it provides adequate strength for typical pipe diameters and is compatible with most hanger bracket systems. M8 is suitable for light-duty residential pipework. For larger pipe diameters (150 mm and above) or heavy services, M12 is common. Always check the hanger bracket manufacturer's specification for the required rod diameter and grade. How do you cut threaded rod without ruining the thread? Use the nut trick: thread two nuts onto the rod and lock them against each other (jam nut technique) at the cut mark. Use the nut face as a guide for your hacksaw or angle grinder. After cutting, back the locked nuts off past the cut end — as they unwind over the freshly cut thread, they reform and clean any minor burring. Always run a loose nut over the finished end to confirm it threads smoothly before putting the rod into service. What is a coupling nut and how do you use it to extend threaded rod? A coupling nut (also called an extension nut, long nut, or rod joiner) is a long hex nut threaded along its full length. To join two lengths of threaded rod, thread one rod end in from each side of the coupling nut until both rods meet approximately at the centre, then tighten with two spanners — one holding the nut, one turning the rod. Ensure the cut ends are clean and deburred before assembly, and achieve full thread engagement for a reliable connection. Can I use threaded rod as an anchor bolt in concrete? Yes — post-installed anchor rods are a common application. The rod is set into a core-drilled hole using two-component epoxy adhesive (such as Loctite 5088 or Ramset HIT-RE 500) and allowed to cure before loading. The grade of rod must match the structural specification — Grade 8.8 is typically required for structural anchors. Always follow the adhesive manufacturer's installation instructions for hole diameter, embedment depth, cleaning procedure, and cure time, and consult a structural engineer for load-critical anchor design. What is the difference between acme thread and standard metric threaded rod? Standard metric threaded rod has a V-shaped thread profile (60° flank angle) designed for fastening — clamping two parts together under static load. Acme thread has a trapezoidal profile (29° flank angle) designed for power transmission — converting rotation into controlled linear motion with reduced friction and better wear characteristics. If you need a leadscrew for CNC, a lathe carriage screw, or a vise screw, you need acme thread rod, not standard allthread. What does 'hanger rod' mean? Hanger rod is the HVAC and fire protection industry term for threaded rod used to suspend ductwork, pipe, cable tray, and mechanical plant from structural steel or a concrete soffit. Hanger rod is typically Grade 4.6 HDG in M10 or M12, passed through a concrete anchor or beam clamp at the top and terminated with a nut and hanger bracket at the bottom. The length is adjusted by running the nut up or down the rod before locking in position. What is stud rod? Stud rod is another name for threaded rod — used primarily in the MEP (mechanical, electrical, and plumbing) trades. The term emphasises the rod's function as a suspension stud — passed through a strut channel fitting or hanger bracket — rather than its product form. It means the same product as allthread, studding, or threaded bar. Can I use threaded rod instead of a bolt? Yes, with two nuts — one on each side of the joint, tightened together to clamp. Threaded rod with two nuts is functionally equivalent to a bolt and nut, and is preferred when you need an adjustable length, when standard bolt lengths are insufficient for your joint thickness, or when you need a fastener that can be positioned anywhere along its length. For volume production, a headed bolt is faster to install. For adjustment, custom lengths, or through-bolt applications with no head clearance, threaded rod is the better choice. What size threaded rod is used for HVAC duct hangers? M10 and M12 are the most common sizes for commercial HVAC duct hangers in Australia. M10 HDG rod is standard for light to medium rectangular ductwork (up to around 600 mm wide). M12 is used for heavier duct runs, larger dimensions, and where spans between hanger points are greater. For heavy plant items — large AHUs, rooftop units — M16 or M20 Grade 8.8 rod may be required. Check the duct weight and hanger spacing against the hanger system manufacturer's load tables. Is 316 stainless threaded rod worth the extra cost over 304? Only if your environment genuinely requires it. Grade 304 handles most corrosive environments well — general outdoor, wet areas, food prep surfaces, mild chemical exposure. Grade 316's additional molybdenum provides meaningfully better chloride resistance, which matters in coastal or marine settings, salt water immersion, swimming pool environments, and food processing plants using chlorinated cleaning compounds. If you're more than a few kilometres from the coast and not dealing with chlorinated chemicals, 304 is usually adequate and significantly cheaper. When in doubt, go 316 — the cost difference is much smaller than a replacement job in a failed anchor. Where can I buy threaded rod in Sydney? AIMS Industrial stocks Grade 4.6 galvanised, Grade 8.8 high tensile, and stainless steel threaded rod in common metric sizes from our Milperra warehouse. Orders placed before our cut-off can be dispatched same day. We supply tradespeople, engineers, and procurement teams across Greater Sydney and Australia-wide. Browse our allthread range online or contact our team for cut-to-length, large quantities, or sizes not shown online. Pair this guide with our Tap Drill Size Chart for the right pilot drill diameter at every tap size. People Also Ask — Threaded Rod Q: What is threaded rod used for in construction and industry? Threaded rod (all thread) is used to hang, suspend, or connect structural elements — such as pipe hangers, suspended ceilings, and anchor bolt applications — and for threaded connections where a standard bolt head cannot be accommodated. It can be cut to any length on site with a hacksaw or angle grinder. Q: What are the common names for threaded rod? Threaded rod is also called all-thread, allthread, studding, stud, and threaded bar. The terms are used interchangeably. The defining characteristic is that the rod is threaded along its full length or a substantial portion of it with no unthreaded shank. Q: What do the property class markings on threaded rod mean? The property class indicates the minimum tensile strength of the rod. Class 4.8 is a standard mild steel grade for general use. Class 8.8 is a higher-tensile grade for more demanding structural applications. Higher classes carry correspondingly higher load capacities. Q: What is the difference between zinc-plated and hot-dip galvanised threaded rod? Zinc-plated rod has a thin electroplated zinc coating suitable for indoor or lightly corrosive environments. Hot-dip galvanised rod has a much thicker coating applied by immersion in molten zinc, providing significantly greater corrosion protection for outdoor and coastal applications — but the thicker coating can affect thread fit with standard zinc-plated nuts. Q: When should you specify stainless steel threaded rod? Stainless threaded rod is selected for applications requiring corrosion resistance beyond what galvanising provides — such as chemical environments, coastal installations, and food processing facilities. Grade 316 stainless offers greater chloride resistance than grade 304 and is preferred in marine or high-chloride settings. Q: What is coil rod and can I use standard nuts on it? Coil rod (coil thread rod) has a different thread profile — round crests rather than the standard V-form used on metric threaded rod. It is used in formwork tie systems, rebar tying and some proprietary concrete accessories, and is NOT interchangeable with standard metric threaded rod or standard hex nuts. Coil rod requires matching coil-thread hardware. Q: When would I use brass or nylon threaded rod instead of steel? Brass threaded rod is used for electrical applications requiring non-magnetism, light corrosion resistance, or aesthetic finish — marine fittings, electrical panel grounding studs, and decorative furniture. Nylon threaded rod is used for electrical isolation, chemical resistance, and applications requiring a non-conductive fastener — circuit boards, chemical plant and food-grade equipment. Neither brass nor nylon threaded rod is suitable for structural use; both are significantly lower in strength than steel. Q: What size threaded rod is used for fire sprinkler pipe hangers? M12 HDG (hot-dip galvanised) is typical for standard commercial sprinkler installations. Sprinkler pipe hangers are installed to AS 1530, with fire contractors applying strict requirements on hanger spacing, rod diameter and anchor type. HDG or stainless rod is used for sprinkler hangers and brace rods depending on the environment. Q: What standard governs threaded rod grades in Australia? Grade 4.6 mild steel threaded rod is manufactured to DIN 976 / AS 2451. Grade 8.8 high-tensile threaded rod is manufactured to DIN 976 / AS 3501. Both are available in zinc-plated, hot-dip galvanised (HDG) and plain (bare steel) finishes for Grade 4.6, and zinc-plated or HDG for Grade 8.8. Never substitute Grade 4.6 for Grade 8.8 in structural applications — the tensile strength difference (400 MPa vs 800 MPa minimum) is material to the design.
Read moreClevis Pin Guide: Types, Sizes, Materials, and Retention Methods
A clevis pin is an unthreaded cylindrical fastener that passes through a clevis bracket and a mating component to form a pivoting joint. Unlike a bolt, a clevis pin is retained at the open end by a split pin, R-clip or nut rather than by threading — making the joint quick to assemble, disassemble and adjust while allowing free rotation between the connected parts. Clevis pins are found throughout Australian industry: tractor three-point linkages, hydraulic ram ends, conveyor pivot arms, wire rope turnbuckle jaws, rigging assemblies, trailer couplings and agricultural implement connections all rely on them. This guide covers types, DIN 1444 metric sizes, materials, retention methods and how to identify a replacement when you no longer have the original specification. Clevis Pin Sizes — Metric Reference Table (DIN 1444) — Quick Reference The table below covers the most common DIN 1444 Form B metric clevis pin sizes stocked in the Australian market. Lengths shown are standard stock lengths; non-standard lengths are available to order for volume requirements. Nominal Diameter Common Stock Lengths Cross-Hole Dia. Typical Application 5mm 20, 25, 30mm 1.6mm Light linkages, small instrument pivots, light sheet metal brackets 6mm 20, 25, 30, 40mm 2.0mm Small hydraulic linkages, light conveyor pivots, bicycle and light vehicle linkages 8mm 25, 30, 40, 50mm 2.5mm Medium equipment pivots, small brake and throttle linkages, light implement connections 10mm 30, 40, 50, 60mm 3.2mm Agricultural 3-point linkage (light implements), medium machinery pivots, gate hardware 12mm 40, 50, 60, 80mm 4.0mm Heavy agricultural connections, trailer pivot points, medium hydraulic cylinder pins 16mm 50, 60, 80, 100mm 5.0mm Drawbar connections, heavy plant pivots, large trailer coupling connections 20mm 60, 80, 100, 120mm 6.3mm Heavy construction plant, large hydraulic rams (boom and arm pins), marine rigging assemblies 25mm 80, 100, 120, 150mm 8.0mm Very heavy plant, large rigging assemblies, mining equipment pivots 30mm 100, 120, 150mm 8.0mm Heavy-duty lifting gear, large mining and earthmoving equipment pivot connections What Is a Clevis Pin? The name comes from the clevis — a U-shaped or forked bracket with aligned holes through both ears. The clevis pin slides through one ear, then through the mating part (a rod eye, chain link, shackle or bracket), then out through the other ear. A retaining device through the cross-hole at the exposed end prevents the pin from backing out. Clevis pin retention via cotter pin is one method — for the castellated-nut-plus-cotter-pin alternative used on rotating shafts and wheel hubs, see the AIMS castle nut guide. Because the pin is unthreaded and free to rotate within the hole, it creates a true pivot joint: the connected components can rotate relative to one another around the pin axis without generating thread fatigue or loosening torque. This is why clevis pins are preferred over bolts wherever cyclical rotation, oscillation or angular movement occurs under load. The three-part assembly — clevis bracket, clevis pin, retaining device — is one of the oldest and most reliable mechanical joints in engineering. In the Australian agricultural and industrial context, you will see it referred to variously as a hitch pin, drawbar pin, linch pin (though that is technically a different fastener) or simply a clevis. Whatever the local name, the geometry and function are identical. A clevis pin is a shear-loaded fastener. In double-shear (the standard clevis arrangement where both ears of the bracket are engaged), the pin carries the applied load across two shear planes simultaneously. This is more efficient than a bolt in the same arrangement, and is why clevis pins of modest diameter can handle surprisingly high loads when the material and geometry are correctly matched to the application. Types of Clevis Pins Standard Clevis Pin (DIN 1444 Form B) The most common type. Has a domed or flat head at one end and a cross-hole drilled through the shank near the other end for a split pin or R-clip. Available in metric diameters M5 through M30 and a range of grip lengths. This is the pin you will find in most general industrial, agricultural and lifting applications in Australia. The Form B designation confirms the cross-hole is present — Form A (no cross-hole) is less common and used only where an alternative retention method is designed into the assembly. Headless / Shoulder Clevis Pin Used where the pin must pass through from one side only, or where head clearance above the clevis ear is restricted. Common in hydraulic cylinder rod-end and base-end connections and precision pivot assemblies on production machinery. The shoulder (a step-down diameter) provides the retention face at one end; the cross-hole or snap-ring groove retains the other end. On hydraulic cylinders, the shoulder pin is often retained by a snap ring (circlip) seated in a groove machined into the clevis ear rather than by an external split pin. Multi-Hole Clevis Pin Has multiple cross-holes drilled along the shank at regular intervals, allowing the effective grip length to be adjusted without removing the pin from the clevis assembly. Used extensively in three-point linkage systems, cultivator frames, toolbar connections and implement height adjusters, where the operator needs to set depth or position increments in the field without a toolkit. The Champion CPMH01 range stocked by AIMS is a typical example: two or more holes let the operator select the engagement point by repositioning the R-clip. Threaded-End Clevis Pin Has a standard domed head at one end and a threaded shank at the other, retained by a nyloc nut and washer. Used in applications where positive, non-backing-out retention is required and tool access at the retention end is available. Less common in field-service applications than the split-pin type but preferred in fixed machinery where vibration is high and the joint is not designed for frequent adjustment. The nut should be tightened to a snug fit — not hard torqued — to preserve free rotation of the pin in the clevis. DIN 1444 — The Standard That Applies in Australia Australian industry uses metric clevis pins manufactured to DIN 1444 (German standard, widely adopted internationally), which defines two forms: Form A — head only, no cross-hole. Used where the pin is retained by another method (circlip groove, grub screw, press fit) or where the assembly is not intended for field disassembly. Form B — head plus cross-hole drilled through the shank near the retention end. The standard workshop and field-service pin. This is what AIMS stocks and what you will find in most hardware and industrial supply catalogues in Australia. The DIN 1444 standard specifies nominal diameter, tolerance class (typically h11 — a slightly loose fit to allow rotation), cross-hole diameter and position, and head dimensions. The h11 tolerance means a 10mm DIN 1444 clevis pin will have an actual diameter of 9.94–10.00mm. The mating clevis holes are typically drilled to 10.5mm (normal fit) for easy assembly and to allow the joint to rotate freely without binding. The standard also specifies the cross-hole diameter relative to pin diameter, so split pins and R-clips sized to the pin will fit correctly without play. A 10mm DIN 1444 pin has a 3.2mm cross-hole; a 12mm pin has a 4.0mm cross-hole; a 16mm pin has a 5.0mm cross-hole. This relationship is what allows you to select the correct split pin simply by knowing the clevis pin diameter. Imperial clevis pins made to ANSI/ASME standards are still in use in Australia, primarily on older US-manufactured agricultural equipment, some British-origin machinery and North American-sourced trailers and attachments. These use inch-fraction diameters and their cross-holes are sized to inch-fraction split pins and R-clips. Where you have a mix of metric clevis hardware and imperial-specification pins on the same machine, do not interchange them without checking the hole sizes match — the dimensional tolerance system differs between DIN and ANSI. Clevis Pin Sizes — Metric Reference Table (DIN 1444) The table below covers the most common DIN 1444 Form B metric clevis pin sizes stocked in the Australian market. Lengths shown are standard stock lengths; non-standard lengths are available to order for volume requirements. Nominal Diameter Common Stock Lengths Cross-Hole Dia. Typical Application 5mm 20, 25, 30mm 1.6mm Light linkages, small instrument pivots, light sheet metal brackets 6mm 20, 25, 30, 40mm 2.0mm Small hydraulic linkages, light conveyor pivots, bicycle and light vehicle linkages 8mm 25, 30, 40, 50mm 2.5mm Medium equipment pivots, small brake and throttle linkages, light implement connections 10mm 30, 40, 50, 60mm 3.2mm Agricultural 3-point linkage (light implements), medium machinery pivots, gate hardware 12mm 40, 50, 60, 80mm 4.0mm Heavy agricultural connections, trailer pivot points, medium hydraulic cylinder pins 16mm 50, 60, 80, 100mm 5.0mm Drawbar connections, heavy plant pivots, large trailer coupling connections 20mm 60, 80, 100, 120mm 6.3mm Heavy construction plant, large hydraulic rams (boom and arm pins), marine rigging assemblies 25mm 80, 100, 120, 150mm 8.0mm Very heavy plant, large rigging assemblies, mining equipment pivots 30mm 100, 120, 150mm 8.0mm Heavy-duty lifting gear, large mining and earthmoving equipment pivot connections A note on grip length: The grip length is the usable shank length between the underside of the head and the centre of the cross-hole. When ordering, confirm that the grip length matches the combined thickness of the clevis ears and the mating part. The cross-hole should clear the outer clevis ear face by at least 3–5mm to allow the split pin legs to be spread or the R-clip to seat fully. Tolerance and fit: DIN 1444 Form B pins are manufactured to h11 tolerance. The mating hole in the clevis bracket should be drilled to H12 tolerance for a normal running fit, or H11 for a close fit. For standard off-the-shelf clevis hardware (turnbuckles, connecting links, hydraulic cylinder rod ends), the clearance fit is designed into the product — simply match the pin diameter to the specified pin size for that fitting. Imperial Clevis Pin Sizes For workshops maintaining older US-origin or British-origin equipment, the following imperial sizes are the most commonly encountered in Australia. Imperial sizes are typically specified in fractional inches for the diameter and whole or fractional inches for the length. Imperial Diameter Metric Equivalent Common Lengths Typical Application 3/16" 4.76mm 3/4", 1", 1-1/4" Light implement connections, cable clevis fittings 1/4" 6.35mm 3/4", 1", 1-1/2" Small drawbar links, trailer safety chain connections 5/16" 7.94mm 1", 1-1/2", 2" Medium agricultural attachments, light lifting hardware 3/8" 9.53mm 1", 1-1/2", 2", 2-1/2" Standard implement hitch pins on older US equipment 1/2" 12.7mm 1-1/2", 2", 2-1/2", 3" Drawbar clevis connections, heavy implements 5/8" 15.88mm 2", 2-1/2", 3", 4" Heavy drawbar, tractor three-point top link (US-spec) 3/4" 19.05mm 2-1/2", 3", 4", 5" Heavy plant, large trailer couplings, US-spec drawbars The Metric/Imperial Crossover Problem in Australian Agriculture This is a real practical issue. Many tractors and implements sold in Australia from the mid-2000s onwards — particularly Chinese-manufactured machines sold under Australian brand names — use clevis geometry that sits between the metric and imperial systems. A nominally 10mm metric clevis hole may accept a 3/8" (9.53mm) imperial pin with slightly looser clearance, and vice versa. This occurs because the Chinese manufacturing supply chain has historically mixed metric and imperial tooling, and the dimensional differences at these sizes are small enough that the pin physically fits even though it is not the correct specification. The practical guidance: if you are replacing a worn pin on Asian-origin equipment and cannot find the original specification, measure the clevis hole diameter in millimetres. If the measurement is exactly a metric value (10.0mm, 12.0mm, 16.0mm), specify a DIN 1444 metric pin. If the measurement corresponds to an imperial fraction (9.5mm ≈ 3/8", 12.7mm = 1/2"), specify an imperial pin. If in doubt, specify the metric size that is closest to the measurement and check the fit before committing to a batch. A metric DIN 1444 pin is usually the safer choice in Australia as it is more widely stocked and its tolerance system is better documented. Clevis Pin Materials Mild Steel, Zinc-Plated (Grade 4.6 Equivalent) The standard material for general industrial and agricultural use. Zinc electroplating (typically 5–8 microns) provides moderate corrosion resistance suitable for sheltered environments, workshop use and most field conditions where the pin will be periodically replaced as a wear item. The steel substrate is mild steel with a minimum tensile strength of around 400 MPa, adequate for the shear loads in standard DIN 1444 applications. Hot-dip galvanised clevis pins are also available for outdoor agricultural applications where corrosion resistance must outlast a regular maintenance cycle. The thicker zinc layer (85 microns minimum to AS/NZS 4680) provides significantly better protection at the cost of slightly reduced dimensional precision. Zinc-plated mild steel is not suitable for permanently wet, coastal, food-processing or chemical environments. In those applications, specify stainless steel. Grade 316 Stainless Steel The correct choice for marine, coastal, food-processing and chemical-processing environments. Grade 316 contains 2–3% molybdenum, which provides significantly better pitting and crevice corrosion resistance than Grade 304 in the presence of chlorides — including seawater, salt-laden coastal air and chlorinated cleaning solutions. If a clevis pin is used in rigging on a boat, near a harbour, in carwash equipment, in seafood processing, in coastal outdoor applications or in any chemical plant with halide exposure, Grade 316 is the minimum acceptable specification. Tensile strength of 316 stainless is typically 515–690 MPa depending on temper and form — comparable to Grade 4.6 mild steel for most clevis pin applications. The significant benefit is corrosion resistance, not strength. Do not substitute Grade 304 for Grade 316 in saltwater or chloride environments. Crevice corrosion and pitting failure in Grade 304 clevis pins used in marine rigging is a documented failure mode that can lead to pin seizure, fracture or the inability to disassemble the joint. Grade 304 Stainless Steel Suitable for general corrosion resistance in non-marine, non-chloride environments. Commonly used in food-preparation areas where cleaning agents are mild (no chlorine-based sanitisers), in refrigeration equipment, in light outdoor applications not subject to salt exposure, and in chemical environments where chlorides are absent. Grade 304 is significantly cheaper than Grade 316 and is adequate for many industrial applications, but its chloride corrosion resistance limit must be respected. High-Tensile Steel (Grade 8.8 Equivalent and Above) Used where a clevis pin is load-rated and the shear strength of a standard DIN 1444 Grade 4.6 equivalent pin is insufficient for the application. Lifting shackle pins, clevis shortening hooks, crane rigging hardware and rated agricultural drawbar connections use high-tensile or alloy steel pins with defined Working Load Limits (WLL). These are not general-purpose DIN 1444 pins — they will have a WLL, grade marking and/or traceability number stamped on them. They must be used within their rated limits and must not be substituted with standard commercial clevis pins. AIMS stocks rated clevis lifting hardware (Grade 80 and Grade 100 clevis hooks and master links) as separate products from the standard DIN 1444 pin range. If you are selecting a pin for a safety-critical or load-rated lifting application, contact AIMS to confirm the correct rated product. Retention Methods Split Pin (Cotter Pin) The most common retention method for DIN 1444 Form B clevis pins. A split pin — also called a cotter pin in American usage — is inserted through the cross-hole and the two legs are spread outward (typically at 90° to each other, with one leg bent back) to resist withdrawal. The split pin provides positive, visible retention: if the split pin is missing, the joint is immediately identifiable as unretained. Split pins are one-use items — once bent, they must be replaced on reassembly. Attempting to re-use a bent split pin risks fatigue fracture of the leg during or after installation. Always carry spare split pins of the correct diameter when working on agricultural or industrial equipment in the field. See the Split Pin & Cotter Pin Guide for full sizing, types and installation guidance. Size the split pin to the cross-hole diameter in the DIN 1444 specification for the pin diameter. R-Clip (Hairpin Cotter / Lynch Pin) A spring-steel wire formed into an R or hairpin profile that clips through the cross-hole and springs outward to resist withdrawal. Tool-free installation and removal — the key advantage over split pins in applications where the joint is frequently adjusted: agricultural implement depth settings, drawbar length adjusters and toolbar connection points. R-clips are reusable through many cycles. R-clips must be inspected regularly and replaced when fatigued. A correctly tensioned new R-clip provides substantial retention force from the spring action; a worn, flattened or permanently deformed R-clip may fall out of the cross-hole under vibration. R-clips are the correct choice for frequently adjusted connections, but are not the right choice where positive, tamper-evident retention is required and the joint is rarely disassembled. Wire Lock Pin (Safety Pin) A solid pin body with an integrated spring-wire lock. The wire passes through the cross-hole and locks automatically. Provides secure, vibration-resistant retention while remaining tool-free for removal. Used on lifting equipment, safety-critical pivot connections and applications where an R-clip may vibrate loose under sustained cyclic loading. The wire lock must be fully seated in the cross-hole to be effective — inspect before use. Nut and Washer (Threaded-End Pins) For threaded-end clevis pins, a standard or nyloc nut with a flat washer provides the retention. The nut should be tightened to a snug fit that eliminates axial float — not torqued hard, as over-tightening binds the joint and generates lateral side loads on the pin. Use a nyloc nut wherever vibration is present to prevent self-loosening. In high-vibration applications, a castle nut with a split pin through a drilled shank may be the most reliable option. Roll pins serve a different retention function — they lock a component to a shaft by interference fit rather than retaining a pin against withdrawal. For gear, sprocket, and lever retention on rotating shafts using a spring steel roll pin, see the Roll Pin (Spring Pin) Guide. Agricultural and Heavy Equipment Applications Clevis pins are among the most frequently replaced consumable fasteners in Australian agricultural and construction equipment. The high-cycle loading of three-point linkage connections, hydraulic top link attachments and drawbar links causes progressive wear in both the pin and the clevis ears, typically appearing as a loose, rattling joint before connection failure. Three-Point Linkage (3PL) Pins Australian tractor manufacturers generally follow the ASAE/ISO Category system for three-point linkage pin dimensions. These are commonly referred to as Cat 1, Cat 2 or Cat 3 pins in Australian rural supplies: Category 1: Lower link pin 22.4mm diameter, top link pin 19.3mm diameter. Suits compact and mid-range tractors. Category 2: Lower link pin 28.7mm diameter, top link pin 25.5mm diameter. Suits medium to large farm tractors. Category 3: Lower link pin 37.4mm diameter, top link pin 31.8mm diameter. Suits large four-wheel drive tractors and high-horsepower implements. Standard Australian rural supply outlets stock pins to these specifications in mild steel (zinc or galvanised), Grade 316 stainless, and hardened steel for high-wear applications. Category pins are retained by R-clips or lynch pins in almost all field applications for ease of implement changeover. Hydraulic Cylinder Connections Hydraulic cylinder rod-end and base-end clevis connections use shoulder or headless pins in most designs. The pin diameter is specified in the cylinder's engineering data and must be matched exactly — an undersized pin will wear rapidly under the side-loading from cylinder force vectors. On excavators, loaders and agricultural hydraulic systems, these pins are designed as replaceable wear items with defined service intervals. Hardened or case-hardened pins are preferred in high-cycle applications to extend service life. Drawbar and Towing Connections Drawbar clevis connections on trailers and agricultural equipment use larger-diameter pins (typically 16–32mm) and must be selected to carry the drawbar tongue weight and dynamic tow loads. In transport applications subject to Australian Road Rules requirements, the pin and clevis assembly must meet the coupling rating (typically expressed as a D-value or tow rating in the vehicle or equipment certification). Do not substitute a lighter pin for a rated tow coupling pin. Marine and Rigging Applications Clevis pins in marine rigging are a specialised application with requirements distinct from general industrial use. Wire rope terminations (swaged fittings, Sta-Lok, Norseman), turnbuckle jaw ends and chainplates all rely on clevis pins that must meet a different standard: Material without exception: Grade 316 stainless steel in all saltwater environments. Grade 304 is not acceptable. Retention: In standing rigging, clevis pins are typically retained with a stainless split ring (cotter ring) rather than a split pin, to prevent sharp bent-leg ends from snagging sails, lines or crew. Some class rules and manufacturers specify a specific retention method — check the rig specification before changing pin or retention type. Dimensional match: Marine clevis fittings are designed to a specific pin diameter and the WLL is rated for that exact diameter. Do not mix pin diameters across a fitting family. Inspection interval: Standing rigging clevis pins should be inspected at each annual rig inspection and whenever the rig is unstepped. Look for pitting, crevice corrosion at the pin-to-fitting interface, surface blistering and any visible bending of the pin shank. Clevis pins in load-rated rigging hardware — bow shackles, dee shackles, clevis shortening hooks, master links — are purpose-designed components with defined WLLs and are not interchangeable with standard DIN 1444 pins. See the Bow Shackle Guide for load-rated rigging hardware. For turnbuckles with jaw (clevis) ends, see the Turnbuckle Guide. Clevis Pin Inspection and Maintenance Clevis pins are wear items. In high-cycle or abrasive applications, periodic inspection and timely replacement prevents joint failure and the associated downtime and safety risk. What to Inspect Pin diameter wear: Measure the pin at the primary shear plane (midpoint between the clevis ears, where loading is concentrated). More than 5% reduction from nominal diameter is cause for replacement. For a 12mm pin, that is 11.4mm — visible with a vernier caliper. Flats and grooving: A pin that has been prevented from rotating (by a too-tight fit or a seized cross-hole) will develop wear flats on one side. A grooved or flatted pin should be replaced even if the diameter reduction is less than 5%, as the remaining section at the wear flat may be below the load-bearing minimum. Cross-hole condition: Check that the cross-hole is clear, the edges are not mushroomed, and a new split pin or R-clip will seat correctly. A mushroomed cross-hole mouth prevents proper split pin installation and is a sign of previous incorrect assembly (oversized split pin forced through). Clevis ear condition: Inspect the clevis bracket holes as well as the pin. An oval hole (worn from round) accelerates further pin wear and may allow the pin to shift laterally under load. A mildly oval hole can sometimes be reamed to the next standard size up with a matching larger pin; a severely worn or cracked clevis ear requires bracket replacement. Corrosion: Surface rust on zinc-plated pins is cosmetic; pitting that has reduced the shank cross-section is cause for replacement. In stainless pins, look for crevice corrosion (dark discolouration at the pin-to-fitting interface) and pitting in the shank. Do not abrade or polish away pitting — replace the pin. Lubrication Clevis pins in rotating or oscillating applications benefit from periodic lubrication. A light application of general-purpose grease at assembly reduces friction-induced wear and helps prevent fretting corrosion at the shear plane. In agricultural equipment, a grease nipple in the clevis ear body is common practice on high-wear connections. In marine applications, anti-seize compound (not grease) on stainless pins prevents galling during assembly and reduces crevice corrosion risk at the pin-fitting interface. How to Choose the Right Clevis Pin Follow these steps to select the correct clevis pin for any application: Step 1 — Determine the required diameter Measure the hole diameter in the clevis ears with a vernier caliper. The pin diameter should be a close sliding fit — for a DIN 1444 h11 tolerance pin in a standard H12 clevis hole, there will be approximately 0.1–0.3mm clearance. If the clevis hole has worn oval, ream it to the next standard size up and fit a correspondingly larger pin. Step 2 — Determine the required grip length Measure the combined thickness of both clevis ears and the mating component at the pin centreline. The grip length of the pin (from head underside to cross-hole centre) should equal this combined thickness, plus 3–5mm to allow the split pin or R-clip to be fitted clear of the outer ear face. If the mating component has a boss or bearing surface that floats axially on the pin, account for the full float range when calculating the required grip length. Step 3 — Select the pin form For most agricultural, industrial and maintenance applications: DIN 1444 Form B (drilled cross-hole) with split pin or R-clip. For frequently adjusted connections (implement depth settings, drawbar adjusters): Form B with R-clip. For hydraulic cylinder rod and base-end connections: shoulder/headless type to match the cylinder specification. For adjustable implement toolbar connections: multi-hole type. Step 4 — Select the material General industrial or agricultural in sheltered conditions: mild steel zinc-plated. Exposed outdoor agricultural in wet conditions: hot-dip galvanised. Coastal, marine, food-processing or chemical environments: Grade 316 stainless. Load-rated lifting or structural: rated clevis pin to WLL specification — not a DIN 1444 commercial pin. Step 5 — Select the retention method Infrequent assembly, safety-critical: split pin (positive, one-use, cheap). Frequent field adjustment: R-clip (reusable, tool-free). High-vibration with infrequent adjustment: wire lock pin or castle nut + split pin. Size the split pin or R-clip to the cross-hole diameter in the DIN 1444 specification for the selected pin diameter — these are directly correlated and documented in the standard. How to Identify a Replacement Clevis Pin When the original pin has been lost, worn beyond recognition or the equipment documentation is unavailable, use this procedure: Measure the clevis hole diameter with a vernier caliper — measure at two points 90° apart to check for oval wear. If the hole is oval, the measurement at the minor axis (smallest diameter) is your target pin size. Record in millimetres. Measure the clevis ear thickness on each ear individually, and the thickness of the mating component. Add these three measurements together for the required grip length (plus the 3–5mm cross-hole clearance allowance). Check the cross-hole position on any remaining section of the old pin — the distance from the tip of the shank to the cross-hole centre tells you whether the grip length calculation is correct. Determine metric or imperial — if the clevis hole measures exactly 9.5mm, 12.7mm, 15.9mm or another imperial inch-fraction equivalent, you are dealing with an imperial-specification fitting. Cross-reference with the imperial size table above. Identify the correct material from the operating environment — marine, coastal or food-processing environment specifies Grade 316 stainless. General industrial or agricultural specifies zinc-plated mild steel unless extended corrosion resistance is needed. Check the retention end geometry — confirm whether the original pin had a drilled cross-hole (DIN 1444 Form B), a threaded end, a snap-ring groove or a different retention feature. Do not fit a Form B pin into an assembly designed for a threaded-end pin without understanding why the design specified threaded retention. If you are unsure after measuring, bring the worn pin (or the clevis ear assembly if it can be removed) to the AIMS counter. Our team can cross-reference to the correct stocked size and confirm material specification. Clevis Pins at AIMS Industrial AIMS stocks a comprehensive range of clevis pins for general industrial, agricultural and maintenance applications across Australia: DIN 1444 Form B metric clevis pins in mild steel zinc-plated — M5 through M30, standard length range Grade 316 stainless steel clevis pins — metric sizes M6 through M20 Imperial clevis pins — 3/16" through 3/4" diameter for maintenance of older US and British-origin equipment Champion CPMH01 multi-hole clevis pins for adjustable implement connections Matching R-clips (hairpin cotters / lynch pins), split pins and wire lock pins View the full clevis pin range at AIMS Industrial → For volume orders, agricultural fleet pin kits, non-standard lengths or help identifying a replacement, contact the AIMS team on (02) 9773 0122 or via the contact page — we carry the reference material to match most applications. Frequently Asked Questions What is a clevis pin? A clevis pin is an unthreaded cylindrical fastener that passes through a U-shaped clevis bracket and a mating component to create a pivoting joint. It is retained at one end by a split pin, R-clip or nut. Unlike a bolt, a clevis pin allows free rotation between the connected parts, making it the correct choice for joints that experience cyclic movement, oscillation or angular displacement under load. What is the difference between a clevis pin and a cotter pin? A clevis pin is the main cylindrical fastener that passes through the joint and carries the load. A cotter pin (split pin) is the retaining device inserted through the cross-hole at the end of the clevis pin to prevent it backing out. They work as a pair — the clevis pin carries the shear load; the cotter pin holds it in place. See the Split Pin & Cotter Pin Guide for full cotter pin sizing and selection. What is another name for a clevis pin? Clevis pins are called hitch pins, drawbar pins, pivot pins or implement pins in Australian agricultural usage. The retaining device may be called a split pin, cotter pin, R-clip, lynch pin or hairpin cotter depending on type and region. In marine rigging the clevis pin may simply be called a rigging pin. Is a clevis pin stronger than a bolt? Strength depends on diameter, material and grade — there is no universal answer. A standard DIN 1444 mild steel clevis pin (Grade 4.6 equivalent) is weaker in shear than a Grade 8.8 bolt of the same diameter. However, clevis pins are designed to operate in double shear and perform well in that loading mode. The correct question is whether the selected clevis pin is appropriately rated for the shear load in the joint — size, material and form matter more than a bolt comparison. What size clevis pin do I need for a Category 1 three-point linkage? Category 1 (ISO 730 / ASAE S217) lower link pins are 22.4mm diameter; the top link pin is 19.3mm diameter. For Category 2 (larger tractors), lower link pins are 28.7mm and top link is 25.5mm. Category 3 uses 37.4mm lower link pins. These are sold as 'Cat 1', 'Cat 2' and 'Cat 3' pins in Australian rural supplies and farm machinery outlets. What is the difference between an R-clip and a split pin for a clevis pin? A split pin (cotter pin) is a single-use, positively retained fastener that is bent through the cross-hole — secure, tamper-evident, but requires tools and must be replaced every time the pin is removed. An R-clip (lynch pin) is a reusable spring-steel wire clip that inserts and removes tool-free, ideal for connections adjusted regularly in the field. For safety-critical or infrequently serviced joints, use a split pin. Inspect R-clips regularly for fatigue and replace if flattened or deformed. What does DIN 1444 mean on a clevis pin? DIN 1444 is a German dimensional standard (widely adopted internationally) that specifies the nominal diameter, tolerance class (h11), cross-hole diameter and position, and head dimensions for clevis pins. Form A has no cross-hole; Form B has a drilled cross-hole for a split pin or R-clip. Purchasing to DIN 1444 ensures dimensional interchangeability with DIN 1444-compliant clevis hardware regardless of manufacturer. Can I use a Grade 304 stainless clevis pin in a marine environment? No — Grade 304 stainless is not suitable for direct saltwater or coastal marine use. It lacks the molybdenum content of Grade 316 and is susceptible to pitting and crevice corrosion in chloride environments. Grade 316 stainless is the correct specification for marine, coastal, offshore and food-processing applications where chlorides are present. In fresh water or sheltered inland environments with no chloride exposure, Grade 304 is acceptable. What is a multi-hole clevis pin used for? A multi-hole clevis pin has several cross-holes along the shank at fixed intervals, allowing the effective engagement depth to be adjusted without removing the pin. Widely used on agricultural implement depth wheels, height adjusters and toolbar connection points where the operator needs quick incremental adjustment in the field without a toolkit. The Champion CPMH01 is a commonly stocked example in Australia. How do I measure a clevis pin? Measure the shank diameter with a vernier caliper at the midpoint of the shank (away from head and cross-hole). Measure overall length from head underside to shank tip. For grip length, measure from head underside to the centreline of the cross-hole. When sizing a replacement, always measure the clevis hole diameter (not the worn pin) — worn pins understate the required size. Measure the hole at two points 90° apart to check for oval wear. Where are clevis pins used? Common Australian applications include tractor three-point linkages and drawbars, hydraulic cylinder rod-end and base-end connections, conveyor and production machinery pivot arms, trailer coupling connections, agricultural implement depth and position adjusters, rigging and lifting hardware (rated versions), marine wire rope fittings, turnbuckle jaw ends, and structural tie-rod connections. What is a headless (shoulder) clevis pin used for? A headless clevis pin is used where there is no clearance for a conventional domed head on the entry side of the joint, or where the pin must insert from either direction. Hydraulic cylinder rod-end pins are the most common application — the pin is retained by a snap ring (circlip) in a groove in the clevis ear rather than by a head. Also used in precision machinery pivots where head clearance above the clevis ear is restricted by an adjacent component. How do I choose the grip length of a clevis pin? The grip length is the usable shank from under the head to the centre of the cross-hole. Add the thickness of both clevis ears plus the part between them, then allow 3 to 5mm past the outer ear so the split pin or R-clip seats clear. Too short and the retainer won't fit; too long and the joint has axial slop. See the clevis pins range. Which coating should an outdoor clevis pin have? For sheltered indoor use, zinc-plated mild steel is fine. For exposed outdoor agricultural use, hot-dip galvanised lasts far longer. For coastal, marine or chemical exposure, use grade 316 stainless — zinc coatings and 304 stainless both corrode in salt air. Match the coating to the environment, not just the load. Why is a clevis pin loaded in double shear? In a standard clevis both ears of the bracket support the pin, so the load is carried across two shear planes at once. This double-shear arrangement lets a modest-diameter pin carry a high load, and is why a clevis pin of a given size is effectively stronger in a clevis than the same pin supported at one end only. Match the pin diameter and material to the load. Besides a split pin, how else can a clevis pin be retained? As well as a split pin (cotter pin), a clevis pin can be held by an R-clip (lynch pin) for tool-free, reusable retention on frequently adjusted joints, by a wire lock pin for vibration-resistant tool-free service, or by a threaded end with a nyloc nut where positive non-backing-out retention is needed. Size the retainer to the cross-hole. See cotter pins for the matching split pins. Need to read an engineering drawing? Our GD&T Symbols Guide explains every common geometric tolerance symbol. Pair this with our Metric Bolt Torque Chart for the recommended tightening torque at every M-series bolt.
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Metric Bolt Torque Chart: Tightening Guide for Grades 4.6, 8.8, 10.9 & 12.9
Getting bolt torque right matters. Too little and the joint works loose under vibration. Too much and you risk stretching the bolt, stripping the thread, or cracking the component. This guide gives you verified torque values for every common metric bolt grade — from the commercial-grade 4.6 through to high-tensile 12.9, plus stainless A2-70 and A4-80 — along with the adjustment factors you need for HDG, oiled, and anti-seize conditions. ⚠️ Important Disclaimer — Read Before Use The torque values in this guide are reference values for general industrial use only. They are calculated to 75% of proof load using a nut factor of K = 0.2 (dry, uncoated steel threads) per ISO 898-1. They are not a substitute for manufacturer-specified torque values, engineering calculations, or professional judgement. Always follow the equipment manufacturer's specified torque for safety-critical, structural, pressure, lifting, and high-cycle applications. Where no manufacturer specification exists, consult a qualified engineer. AIMS Industrial accepts no liability for consequences arising from the misapplication of these values. Quick reference: Use the chart below for tightening torques in Newton-metres (Nm) for metric bolts grades 4.6, 8.8, 10.9 and 12.9, sizes M4 through M24. Values are calculated for clean, dry, uncoated steel threads — apply the lubrication/coating adjustment factors below for HDG, oiled or anti-seize conditions. Working with SAE/imperial bolts instead? See our Imperial/SAE Bolt Torque Chart for Grade 2, 5 and 8 values in UNC and UNF, dry and lubricated, in ft-lb. Metric Bolt Torque Chart — Grades 4.6 / 8.8 / 10.9 / 12.9 The values below are maximum tightening torques in Newton-metres (Nm) for metric coarse-thread bolts with clean, dry, uncoated steel threads (K = 0.2), tightened to 75% of proof load per ISO 898-1. If your threads are lubricated, plated, or coated, apply the adjustment factors in the next section. For diameter, thread pitch and head dimension references that pair with these torque specs, see the AIMS Metric Bolt Size Guide. Size Pitch (mm) Grade 4.6 (Nm) Grade 8.8 (Nm) Grade 10.9 (Nm) Grade 12.9 (Nm) M4 0.70 1.2 3.2 4.4 5.1 M5 0.80 2.4 6.4 8.8 10 M6 1.00 4.1 11 15 18 M8 1.25 10 26 37 43 M10 1.50 20 52 72 84 M12 1.75 34 91 126 147 M14 2.00 54 145 200 234 M16 2.00 85 226 313 366 M18 2.50 117 301 430 503 M20 2.50 165 426 610 713 M22 2.50 225 580 830 970 M24 3.00 286 737 1,055 1,233 Values calculated per ISO 898-1 at 75% proof load, K = 0.2 (dry uncoated steel). Reference values only — see disclaimer above. How to Identify Your Bolt Grade Before you can look up a torque value, you need to know your bolt's grade. Metric bolt grades are stamped on the head. The most common markings you'll encounter in Australian industry are: Torque-to-yield is the standard tightening pattern — but on castellated (castle) nut assemblies the procedure is different: torque to spec, then back off to the next slot alignment for the cotter pin. See the castle nut guide for the full back-off-to-slot procedure. 4.6 — Commercial grade. General-purpose carbon steel, low strength. Often used in non-critical structural and general fabrication work where high-tensile fasteners are not required. 8.8 — High-tensile. The most widely used grade in Australian engineering and manufacturing. Identified by "8.8" on the bolt head. 10.9 — Very high-tensile. Used in high-load applications such as automotive, heavy machinery, and structural connections subject to dynamic loading. 12.9 — Ultra-high-tensile. The highest standard metric bolt grade. Socket head cap screws are commonly grade 12.9. Not for use in corrosive environments without appropriate coating. A2-70 / A4-80 — Stainless steel. A2 is 304 stainless; A4 is 316 marine grade. The number indicates tensile strength (700 MPa and 800 MPa respectively). Note: stainless bolts require lower torque values than carbon steel of equivalent strength — see the stainless table below. No marking on the head? The bolt is likely a low-grade commercial fastener — treat it as 4.6 and do not apply high-tensile torque values. For a full guide to bolt markings and grade comparisons, see the AIMS bolt grade chart. The same grade designations and torque values in this guide also apply to threaded rod (allthread) — the torque spec is identical to a bolt of the same grade and diameter. Stainless Steel Bolt Torque Chart — A2-70 and A4-80 Stainless bolts require separate torque values for two reasons. First, their mechanical properties differ from carbon steel grades of the same approximate strength. Second — and more importantly — stainless-to-stainless threads are prone to galling (thread seizure from cold welding under load). Standard practice is to lubricate stainless threads with a copper-based anti-seize compound before assembly, which also changes the K-factor from 0.2 to approximately 0.13. The table below gives torque values for stainless with anti-seize applied. Size Pitch (mm) A2-70 (Nm) — with anti-seize A4-80 (Nm) — with anti-seize M4 0.70 1.0 1.3 M5 0.80 2.0 2.6 M6 1.00 3.3 4.4 M8 1.25 8.1 10.8 M10 1.50 16 21 M12 1.75 28 37 M14 2.00 44 59 M16 2.00 69 92 M18 2.50 95 127 M20 2.50 135 180 Stainless values calculated with K = 0.13 (copper anti-seize applied), 75% proof load per ISO 3506. Always lubricate stainless threads to prevent galling. Reference values only. Torque Adjustment Factors — Lubrication, Coatings and Plating The main tables above assume clean, dry, uncoated steel threads — a K-factor of 0.2. In reality, bolt threads are often plated, lubricated, or treated. Each condition changes the friction coefficient and therefore the torque required to achieve the same preload. Applying the wrong K-factor for your thread condition is one of the most common causes of incorrect preloading — either stretching bolts by over-torquing an oiled thread with dry-thread values, or under-clamping a dry HDG thread that needs more torque than most charts show. Thread Condition K-Factor Multiply Table Values By Notes Dry, uncoated carbon steel (reference) 0.20 × 1.00 Baseline condition for main table above Electrozinc plated (bright zinc) 0.20 × 1.00 Similar to dry steel; use table values as-is Hot-dip galvanised (HDG) 0.25 × 1.25 Rough zinc coating increases friction — increase torque by 25% vs table values to achieve same preload Lightly oiled (SAE 30 / machine oil) 0.15 × 0.75 Reduce torque 25% vs table values Copper-based anti-seize 0.13 × 0.65 Reduce torque 35%. Standard practice for stainless and high-temperature assemblies Molybdenum disulfide (MoS2 / moly paste) 0.13 × 0.65 Reduce torque 35%. Often used on high-load assemblies. See moly grease guide Loctite threadlocker (anaerobic) 0.15 × 0.75 Loctite acts as a lubricant before cure. Follow Loctite's published torque datasheet for the specific product K-factor values based on VDI 2230 and industry reference data. Apply to Nm values from the main tables above. Example: M12 Grade 8.8 bolt, hot-dip galvanised. Table value = 91 Nm (dry). Adjusted torque = 91 × 1.25 = 114 Nm. Example: M16 Grade 10.9 bolt, oiled threads. Table value = 313 Nm (dry). Adjusted torque = 313 × 0.75 = 235 Nm. Coarse Thread vs Fine Thread — Does Pitch Affect Torque? Yes, but modestly. The standard metric coarse thread is what the tables above cover — it's what the vast majority of industrial bolts use. Metric fine pitch threads (MF) have a smaller thread pitch for the same diameter, which increases the threads-per-unit-length and slightly raises the friction component of the torque equation. Fine pitch bolts of the same grade typically require 8–12% higher torque to achieve the same preload as their coarse-pitch equivalents. In practice, if you're using metric fine pitch bolts (common in precision machinery, automotive, and hydraulic components) and the manufacturer has not provided a torque specification, add approximately 10% to the coarse-pitch table values above. However, manufacturer specifications should always take priority — fine pitch bolts are often used in precision applications where specific torque values are critical. Not sure whether you have coarse or fine pitch? Count the thread pitch with a thread gauge, or refer to the metric fastener thread standards guide. Socket Head Cap Screws — Torque vs Hex Head Bolts Socket head cap screws (also called Allen head bolts or cap screws) are almost always Grade 12.9 for metric sizes. However, their recommended tightening torque is typically set at about 80% of the calculated maximum — because the small hex socket drive is prone to rounding if over-driven, and because SHCS are commonly used in tapped blind holes where thread engagement length matters more than absolute preload. As a working rule: use 80% of the Grade 12.9 values from the main table for standard socket head cap screws in steel, unless the manufacturer specifies otherwise. For example, M10 Grade 12.9 table value = 84 Nm → SHCS working torque ≈ 67 Nm. For aluminium tapped holes, reduce further — typically to 50–60% of the steel value to avoid stripping the softer thread. See the socket head cap screw guide for full selection and torque guidance. K-Factor and Nut Factor Explained The K-factor (also called nut factor or torque coefficient) is the single most important variable in bolt torque calculations — and the one most often misunderstood. It's a dimensionless constant that accounts for all the friction in the joint: under-head friction, thread friction, and a small contribution from thread geometry. The torque formula is: T = K × F × d Where T is tightening torque (Nm), K is the nut factor, F is the desired bolt preload (N), and d is the nominal bolt diameter (m). K is emphatically not a material property — it's an empirical value that depends on thread surface condition, lubrication, plating, thread quality, and the condition of the mating surfaces. Why does this matter? Because K can vary from 0.10 (PTFE-coated fasteners) to 0.35 (corroded or rough threads), and this variation is multiplied directly through the torque calculation. A bolt tightened to 100 Nm with K = 0.20 achieves very different preload than the same bolt tightened to 100 Nm with K = 0.13. For most general industrial work, K = 0.20 (dry uncoated steel) is the correct baseline. For anything critical, verify the K-factor for your specific thread condition before specifying a torque value. Over-Tightening and Under-Tightening — What Goes Wrong Both failure modes are common and both are preventable with correct torque application. Over-tightening stretches the bolt beyond its yield point, permanently reducing its cross-sectional area. Once a bolt yields, it loses its elastic clamping capacity — it cannot be returned to correct preload by retightening, and must be replaced. Repeated over-tightening in aluminium tapped holes strips the thread entirely, often ruining the component. In brittle materials (cast iron, some plastics), the compressive stress under the bolt head can cause cracking around the hole. Galvanised bolts are particularly susceptible because the rougher HDG thread means most mechanics instinctively stop tightening before the bolt has reached the higher torque actually required — but some overcompensate and go too far. Under-tightening is statistically more common and often more dangerous, because the failure is progressive rather than immediate. An under-torqued joint works loose under vibration (the Junker effect), reducing clamping load progressively until the joint either separates or the bolt shears under the resulting bending load. Self-loosening under vibration is virtually eliminated by correct preload — the friction in a properly torqued joint is sufficient to prevent rotation. For vibration-critical applications, combine correct torque with an appropriate threadlocker or locking fastener system. How to Use a Torque Wrench Correctly A torque wrench is only as accurate as its calibration and the technique of the person using it. A few things to get right: Choose the right range. A torque wrench is most accurate at 20–80% of its rated maximum. Using a 500 Nm wrench to torque an M8 bolt to 26 Nm puts you at 5% of range — accuracy drops to ±20% or worse. Use a wrench rated for the torque you're actually applying. For M4–M12 fasteners, a 5–50 Nm wrench is appropriate. For M16–M24, use a 100–500 Nm rated wrench. Pull, don't push. Apply force to the handle in a smooth, steady pull. Jerking or pushing reduces accuracy. For a click-type wrench, stop immediately when you hear and feel the click — continuing to apply force after the click over-torques the bolt. Account for extensions. Adding a socket extension does not change torque as long as the extension is in line with the drive. If you use a side extension to reach an awkward bolt, you introduce a lever arm that changes the effective torque applied — calculate accordingly. Calibration. Click-type torque wrenches should be calibrated annually or every 5,000 cycles, whichever comes first. Store them wound back to the lowest setting — leaving a click wrench at high torque setting compresses the spring and accelerates drift. Beam wrenches and dial wrenches do not require calibration management in the same way, but check that the zero returns correctly before each use. Sequence for multi-bolt joints. For flanges, covers, and head bolts, tighten in a cross pattern (star or cross sequence) in three passes: 30%, 70%, 100% of final torque. This ensures even clamping load distribution and prevents gasket distortion. When to Follow Manufacturer Specifications Instead of This Chart This chart is a general reference. It is not appropriate for the following situations — always use manufacturer-specified torque values or consult a qualified engineer: Structural steel connections. AS 4100 (Steel Structures) and AS 4600 (Cold-Formed Steel) specify installation torque and procedures for structural bolts. 8.8/S and 10.9 structural bolts used in friction-type joints have specific snug-tight and full-pretension procedures that go beyond a simple torque value — see AIMS's dedicated guide to structural bolt tensioning, categories and washer selection under AS 4100 for the full part-turn and DTI washer procedures. Lifting and rigging equipment. Any fastener in a lifting application — eye bolts, shackle pins, crane superstructure, hoist mountings — must be torqued and locked to the manufacturer's specification. No generic chart applies. See the SWL vs WLL vs MBL guide for load rating context. Pressure systems and hydraulic connections. Threaded fittings in hydraulic and pneumatic circuits must be torqued per fitting manufacturer specifications. Applying bolt torque values to hydraulic fittings will almost certainly cause leaks or thread damage. Cylinder head bolts and engine fasteners. These are almost always torque-to-yield and require torque-angle sequences specified by the engine manufacturer. Replace them after any removal. Proprietary fastener systems. Huck bolts, Superbolt tensioners, hydraulic bolt tensioning systems, and similar proprietary solutions have their own installation specifications that override ISO 898-1 calculations. Australian Standards for Metric Fasteners For Australian industry, the key standards governing metric fastener mechanical properties and assembly are: AS/NZS 1110.1 and AS/NZS 1110.2 — Mechanical and physical properties of metric bolts, screws, and studs. These are the Australian adoptions of ISO 898-1 and ISO 898-2. The proof load stress values used in this guide's torque calculations are taken from these standards. AS 4100 — Steel Structures. Governs structural bolt grades, installation method (snug-tight vs fully pretensioned), and minimum edge distances for bolted connections in structural steel. References bolt grades 8.8/S, 10.9/S, and 12.9/HF. AS/NZS 1554 series — Structural steel welding standards, which set requirements where bolted and welded connections are used together. AS/NZS 3992 — Pressure equipment, which sets requirements for bolted pressure vessel and flange connections. For general industrial maintenance and non-structural applications, there is no mandatory Australian standard requiring use of specific torque values. However, Safe Work Australia guidelines require that fastened joints be assembled in accordance with the manufacturer's instructions or, where none exist, to industry-recognised practice — which this guide supports. Frequently Asked Questions What is the torque for an M10 bolt Grade 8.8? For a clean, dry M10 Grade 8.8 bolt, the reference torque is 52 Nm. If the threads are oiled, reduce to approximately 39 Nm. If hot-dip galvanised, increase to approximately 65 Nm. Always confirm with the equipment manufacturer's specification if one exists. What is the torque for an M8 bolt Grade 8.8? For a clean, dry M8 Grade 8.8 bolt, the reference torque is 26 Nm. With lubricated threads, approximately 20 Nm. With HDG threads, approximately 33 Nm. M8 is one of the most commonly used fastener sizes in Australian light industrial and fabrication work. What is the torque for an M12 bolt Grade 8.8? For a clean, dry M12 Grade 8.8 bolt, the reference torque is 91 Nm. HDG adjustment: 91 × 1.25 = 114 Nm. Oiled: 91 × 0.75 = 68 Nm. M12 is common in structural connections, machinery frames, and equipment mounting plates. What is the torque for an M16 bolt Grade 8.8? For a clean, dry M16 Grade 8.8 bolt, the reference torque is 226 Nm. This typically requires a 1/2" or 3/4" drive torque wrench rated for at least 280 Nm. For structural applications under AS 4100, follow the snug-tight and pretensioning procedures rather than a generic torque value. What is the torque for an M20 bolt Grade 8.8? For a clean, dry M20 Grade 8.8 bolt, the reference torque is 426 Nm. At this size, a 3/4" drive torque wrench is typically required. Confirm this is not a structural connection requiring AS 4100 pretensioning procedures before applying a generic torque value. Do I need to reduce torque for lubricated bolts? Yes — significantly. Lubricating threads reduces the K-factor from approximately 0.20 to 0.15, which means the same torque produces about 33% more preload. Applying dry-thread torque values to an oiled bolt will over-tension it. Reduce torque by approximately 25% when threads are lightly oiled with machine oil. With anti-seize (copper or moly), reduce by approximately 35%. What torque should I use for hot-dip galvanised (HDG) bolts? Hot-dip galvanised bolts have a rougher zinc coating that increases thread friction, raising the K-factor to approximately 0.25 vs 0.20 for bare steel. This means you need to apply approximately 25% more torque than the table values to achieve the same preload. Example: M12 Grade 8.8 HDG = 91 × 1.25 = 114 Nm. Many maintenance tradespeople under-torque HDG bolts because they feel stiffer at lower torque values — this is the friction, not the preload. Use a calibrated torque wrench, not feel. What torque should I use for stainless steel bolts? Use the stainless torque table above rather than the carbon steel grades. Always apply copper-based anti-seize compound to stainless threads before assembly to prevent galling (thread seizure). If assembling stainless-into-steel rather than stainless-into-stainless, galling risk is lower but anti-seize is still recommended. The A2-70 and A4-80 values in this guide already assume anti-seize is applied. What happens if I overtighten a bolt? The bolt stretches beyond its yield point, permanently losing its ability to provide correct clamping force. In threaded holes (as opposed to through-bolts with nuts), overtightening can strip the thread — especially in aluminium or cast iron. In flanged joints, overtightening can crush the gasket beyond its recovery range. Once a bolt has been yielded, replace it — retightening will not restore correct preload, and the bolt's fatigue life is compromised. What happens if I undertighten a bolt? The joint lacks sufficient clamping force and can work loose under vibration, thermal cycling, or dynamic loading. Self-loosening is the primary failure mode — the bolt gradually rotates itself out of the joint. In machinery, this creates fretting wear, progressive loosening of adjacent fasteners, and ultimately joint failure. Under-torqued bolts in pressurised systems or lifting equipment create serious safety risks. Use a torque wrench, not feel — the difference between 50 Nm and 80 Nm of torque is imperceptible by hand on an M10 bolt. What bolt grade should I use if there's no marking on the head? Treat it as Grade 4.6 and apply the corresponding torque values. Unmarked bolts are typically low-grade commercial fasteners. Do not apply Grade 8.8 or higher torque values to an unmarked bolt — it may not have the proof load to sustain the preload, and could yield or fracture. For any application requiring Grade 8.8 or higher, use properly marked, certified fasteners from a reputable supplier. Do I always need a torque wrench? For non-critical connections under M8, experienced tradespeople often estimate by feel — but this introduces variability of ±30–50%. For anything M10 and above, structural, pressure-bearing, or vibration-critical, use a calibrated torque wrench. For M16 and above, a torque wrench is effectively mandatory — the clamping loads are too high to judge accurately by feel, and the consequences of a mistake are proportionally greater. What is the difference between coarse and fine pitch torque? Fine pitch metric bolts (MF series) require approximately 8–12% higher torque than coarse pitch bolts of the same grade and diameter to achieve the same preload. In practice, if no manufacturer specification exists, add 10% to the coarse-thread table values for fine-pitch fasteners. Fine pitch bolts are more commonly found in precision machinery, automotive applications, and hydraulic components than in general industrial fastening. What is proof load and how does it relate to torque? Proof load is the maximum tensile force a bolt can sustain without permanent deformation — it's below the yield strength and represents the safe working region of the bolt's elastic range. The torque tables in this guide are calculated to achieve 75% of proof load as preload, which is the standard industrial target: high enough to resist self-loosening, well short of yielding the fastener. The ISO 898-1 proof load for Grade 8.8 is 600 MPa (for diameters up to M16), giving a target preload of 450 MPa — translated to a torque via the K-factor equation. Should I use this chart for thread-forming screws into plastic or aluminium? No. Thread-forming screws (self-tapping, thread-rolling) create their own mating thread and have completely different torque requirements. Applying bolt torque values will strip the formed thread. Use torque values from the screw manufacturer's datasheet, or follow assembly guidelines for the specific material and hole size. As a general guide, thread-forming screw torque is typically 30–60% of a tapped bolt of the same diameter. Need bolts, nuts, or fasteners? AIMS stocks metric fasteners across all grades Grade 4.6 through 12.9, stainless A2-70 and A4-80, hot-dip galvanised — AIMS Industrial supplies metric bolts, nuts, washers, and fasteners to Australian industry. Knowledgeable team, fast dispatch, Sydney-based. Browse bolts All fasteners Talk to a specialist People Also Ask — Metric Bolt Torque Q: Why is it important to torque bolts to the correct specification? Correct torque creates the right clamping force in a bolted joint. Under-torquing leaves the joint with insufficient clamping load, allowing movement, vibration loosening and eventual failure. Over-torquing stretches the bolt beyond its yield point, permanently reducing its tension capacity, or crushes soft materials. Torque-to-yield fasteners are single use for this reason. Correct torque is especially critical in structural, pressure vessel, engine and brake system applications. Q: What is the difference between property class 8.8 and 10.9 bolts? Bolt property class indicates strength. Class 8.8 has a minimum tensile strength of 800 MPa with a proof load of 640 MPa — a general-purpose structural fastener. Class 10.9 has a minimum tensile strength of 1,000 MPa with higher proof load, used where higher clamping forces are required in a smaller footprint. Higher property class bolts require proportionally higher torque to achieve correct preload. Always match the torque specification to the actual bolt property class being used. Q: Does lubricating a bolt change the required torque? Yes, significantly. Standard torque values in most charts assume dry or lightly oiled threads. Applying a thread lubricant such as copper-based anti-seize or molybdenum disulphide grease substantially reduces friction, meaning the same torque creates a much higher clamping force — often 20-30% more than dry. Most manufacturers publish separate torque values for lubricated and dry conditions. Never apply standard dry torque values to heavily lubricated fasteners without checking the manufacturer's lubricated torque specification. Q: What type of torque wrench is best for precision bolt tightening? Click-type (preset) torque wrenches are the most common for precision work — they emit an audible click and release when target torque is reached. Beam-type wrenches are simple and durable but require the user to watch the scale during use. Electronic torque wrenches provide a digital readout and can store data. For critical applications, dial torque wrenches allow continuous monitoring of torque during tightening. Regardless of type, torque wrenches must be calibrated periodically and stored properly to maintain accuracy. Q: Should I torque bolts in a specific sequence when assembling a bolted flange? Yes. Bolted flange joints must be torqued in a cross or star pattern, not in a circular sequence. Tightening in sequence around the circumference introduces uneven loading and gasket distortion. The standard approach is to hand-tighten all bolts first, then apply torque in at least three passes — typically 30%, 70% and 100% of final torque — in a diagonally opposite pattern. This ensures even gasket compression and prevents leakage under pressure. For metric thread forming taps, see our metric thread forming taps range stocked across Australia. AIMS Industrial stocks metric spiral point taps — see the full range for trade and industrial use.Once a fastener is torqued to the figures above, a threadlocker is what keeps it there under vibration — see our Loctite Threadlocker Guide for choosing the right grade by bolt size and whether the joint needs to come apart again.
Read moreMetric vs Imperial Fasteners — Which System Is Standard in Australia
Walk into any workshop in Australia and you will find two fastener systems sitting side by side — metric and imperial. Metric has been Australia's official standard since the 1970s, but imperial threads have never fully disappeared. US-manufactured plant equipment, older British machinery, classic vehicles, and some hydraulic systems all run on threads that metric fasteners simply will not fit. This guide explains how each system works, what you will encounter each one on, and why — despite similar diameters — metric and imperial fasteners are never interchangeable. For a direct conversion table between measurement systems, see the AIMS Fastener Reference Chart. Why Australia Uses Both Fastener Systems Australia formally adopted the metric system under the Metric Conversion Act 1970, with the transition largely complete by the mid-1980s. From that point forward, Australian engineering standards, building codes, and manufacturing specifications switched to metric — ISO threads, millimetre dimensions, metric grade designations. Once you've decided on metric — see the AIMS Metric Bolt Size Guide for the full M3 through M24 reference covering diameter, thread pitch, head dimensions and grade markings across all common head profiles. But metrication did not erase the installed base. Equipment already in the field kept running on its original threads. New equipment imported from the United States arrived — and continues to arrive — with UNC and UNF fasteners, because the US never adopted metric for most industrial applications. British and Commonwealth machinery manufactured before the 1970s used Whitworth threads (BSW and BSF). That legacy still appears daily in maintenance workshops across Australia. The result is a practical reality: anyone maintaining plant, vehicles, or machinery in Australia needs to understand both systems. The consequences of misidentifying a thread are not abstract — stripped fasteners, damaged tapped holes, and joints that appear tight but hold no real clamping force. All of these trace back to using the wrong thread system. The good news is that correctly identifying metric and imperial threads is straightforward once you understand how each system is specified. How Metric Fasteners Are Specified Metric fasteners follow the ISO standard. The designation uses an "M" prefix followed by the nominal outer diameter in millimetres, then the thread pitch in millimetres, then the length in millimetres. An M10 × 1.5 × 40 bolt has a 10 mm nominal diameter, a 1.5 mm thread pitch, and is 40 mm long. When no pitch is stated — for example, just "M10 × 40" — coarse pitch is assumed by convention. The thread angle for ISO metric threads is 60°, measured at the flanks of the thread profile. This is the same flank angle as the Unified thread family (UNC and UNF) used in North America, but the pitch tables are entirely different — a metric bolt and a UNC bolt of similar diameter are not interchangeable despite sharing a thread angle. The table below shows standard metric coarse pitch specifications for common bolt sizes: Metric size Nominal diameter Coarse pitch Fine pitch (MF) Common application M5 5.0 mm 0.8 mm 0.5 mm Small machinery, electronics enclosures M6 6.0 mm 1.0 mm 0.75 mm General hardware, light structural M8 8.0 mm 1.25 mm 1.0 mm Most common general-purpose size M10 10.0 mm 1.5 mm 1.25 mm Structural, flanges, brackets M12 12.0 mm 1.75 mm 1.25 mm Heavy structural, machinery frames M16 16.0 mm 2.0 mm 1.5 mm Steelwork, heavy structural connections M20 20.0 mm 2.5 mm 1.5 mm Heavy plant, large structural joints M24 24.0 mm 3.0 mm 2.0 mm Crane components, heavy fabrication M30 30.0 mm 3.5 mm 2.0 mm Heavy lifting, foundation bolts Metric bolts are specified under Australian Standard AS 1110 (precision hexagon bolts) and AS 1111 (commercial hexagon bolts), which are aligned with ISO 4014 and ISO 4018 respectively. For full metric-to-imperial dimension conversion tables, see the AIMS Fastener Reference Chart. How Imperial Fasteners Are Specified Imperial fasteners specify diameter in inches — either as a fraction (1/4", 3/8", 1/2") or, below 1/4" diameter, as a number designation (#4, #6, #8, #10). Thread count is given in threads per inch (TPI), and the thread standard follows: 3/8"-16 UNC is a 3/8 inch diameter bolt with 16 threads per inch in the Unified National Coarse standard. The thread angle for Unified threads (UNC and UNF) is 60°. Whitworth threads (BSW and BSF) use a 55° flank angle — a fundamentally different thread profile that makes Whitworth fasteners incompatible with both metric and Unified fasteners regardless of pitch. The table below shows standard imperial sizes and pitches for UNC and UNF: Diameter Decimal (inches) UNC TPI UNF TPI Approx metric equivalent (diameter only) 1/4" 0.250" 20 28 ~M6 (6.35 mm vs 6.0 mm) 5/16" 0.313" 18 24 ~M8 (7.94 mm vs 8.0 mm) 3/8" 0.375" 16 24 ~M10 (9.525 mm vs 10.0 mm) 7/16" 0.438" 14 20 ~M11 (no direct metric equivalent) 1/2" 0.500" 13 20 ~M12 (12.7 mm vs 12.0 mm) 5/8" 0.625" 11 18 ~M16 (15.875 mm vs 16.0 mm) 3/4" 0.750" 10 16 ~M20 (19.05 mm vs 20.0 mm) 7/8" 0.875" 9 14 ~M22 (22.225 mm vs 22.0 mm) 1" 1.000" 8 12 ~M25 (25.4 mm vs 25.0 mm) The "approx metric equivalent" column shows only diameter proximity — it does not imply interchangeability. See the near-miss section below for why these diameter similarities are dangerous in practice. Metric Thread Types: Coarse and Fine Within the ISO metric system, two thread pitches cover most applications. Understanding when each is used prevents ordering errors and ensures the right fastener reaches the job. ISO Metric Coarse (MC) is the default for general industrial and structural use. It assembles faster, tolerates slight misalignment, and is less sensitive to contamination in the thread form. When someone says "M10 bolt" without specifying pitch, they almost always mean M10 × 1.5 coarse. Coarse pitch is specified under ISO 261 and covers the vast majority of Australian industrial fastener use. ISO Metric Fine (MF) uses a smaller pitch — more threads per unit length than coarse at the same diameter. This provides finer adjustment, better resistance to loosening under vibration, and is appropriate for thin-walled tapped sections where a coarse thread would not allow enough thread engagement. M10 fine is typically M10 × 1.25; M8 fine is M8 × 1.0. Fine pitch is more common in automotive, aerospace, and precision mechanical applications than in general structural work. Coarse and fine metric nuts of the same diameter are not interchangeable — an M10 × 1.5 nut will not correctly engage an M10 × 1.25 bolt. Always confirm pitch when ordering fasteners for fine-pitch applications, as coarse is typically supplied by default. Imperial Thread Types: UNC, UNF, BSW, BSF and BSP The imperial world contains several distinct thread standards, each with a specific application history. Understanding the differences between them matters — particularly for anyone maintaining legacy equipment in Australia, where all four standards may be encountered on the same site. UNC — Unified National Coarse is the most widely used imperial fastener thread in Australia today. It is the standard for US-manufactured industrial equipment, American-brand hand tools, and most hardware imported from North America. UNC uses a 60° thread angle and is defined in ASME B1.1. It is a coarser pitch than UNF at any given diameter, making it faster to assemble and more tolerant of contamination. Common UNC sizes you will encounter on US machinery: 1/4"-20, 5/16"-18, 3/8"-16, 7/16"-14, 1/2"-13, 5/8"-11, 3/4"-10. The number after the dash is the TPI — so 3/8"-16 UNC has 16 threads per inch. UNF — Unified National Fine uses the same 60° thread form as UNC but with a finer pitch. UNF provides higher tensile strength at a given diameter, better vibration resistance, and finer adjustment range. It is standard in aerospace, automotive precision components, and applications where the joint may be subjected to cyclic loading. Common UNF sizes: 1/4"-28, 5/16"-24, 3/8"-24, 1/2"-20. UNC and UNF bolts of the same diameter look virtually identical — they can only be reliably distinguished with a thread pitch gauge. Never mix UNC and UNF nuts and bolts even within the same imperial system. BSW — British Standard Whitworth is the thread standard found on British and older Australian-made equipment manufactured before metrication. The defining characteristic of BSW is its 55° flank angle — different from both ISO metric and Unified threads — combined with rounded thread crests and roots. BSW is identified by diameter in inches and TPI. BSW is the coarse pitch thread within the Whitworth family. Common BSW sizes encountered on older plant in Australia: 1/4"-20 BSW, 5/16"-18 BSW, 3/8"-16 BSW, 1/2"-12 BSW, 5/8"-11 BSW, 3/4"-10 BSW. Note that some TPI values are shared with UNC — but the 55° Whitworth profile means they are not interchangeable despite having the same TPI. BSF — British Standard Fine uses the same 55° Whitworth thread form as BSW but with a finer pitch. BSF was used on older British precision applications — classic motorcycles, fine adjusters, vintage vehicles, and industrial machinery where higher clamping force was required from the same bolt diameter. BSF is less commonly encountered than BSW, but is still found on specific older equipment, particularly British motorcycles (Triumph, BSA, Norton) and some vintage agricultural machinery. AIMS stocks BSF in key sizes, with less common sizes available to order. If you are unsure whether a fastener is BSW or BSF, a Whitworth thread pitch gauge will identify it — the profile will seat correctly on both, but the TPI will tell you which pitch variant it is. BSP — British Standard Pipe deserves a specific call-out because it is frequently confused with BSW by people who encounter a 55° thread on a fitting and assume it is a fastener thread. BSP is a pipe and fitting thread — used on hydraulic, pneumatic, and plumbing connections — not on nuts and bolts. BSP comes in two forms: BSPP (parallel) and BSPT (tapered, for sealing applications). The 55° thread angle is the same as Whitworth, but BSP's pitch table, diameter designations, and sealing geometry are entirely different from BSW. The practical rule: if you are working on a hydraulic fitting, a pneumatic manifold, or a fluid system, and the thread has a 55° profile, it is almost certainly BSP, not BSW. Never substitute BSP and BSW fasteners or fittings — the thread forms, pitches, and sealing arrangements are incompatible despite the shared flank angle. Are Metric and Imperial Fasteners Interchangeable? No. Metric and imperial fasteners are not interchangeable, and attempting to use them as such is a reliable way to strip threads, damage tapped holes, or create a joint that holds no meaningful clamping force under load. The incompatibility has two sources. First, thread pitch: even where the nominal diameters of a metric and an imperial fastener are close, the pitch in millimetres does not match the pitch implied by the TPI — so a metric nut tightened onto an imperial bolt of similar diameter will cross-thread within a few turns. Second, for Whitworth threads (BSW and BSF), the thread flank angle is 55° versus the 60° of both metric and Unified threads, making the profiles geometrically incompatible regardless of what the diameter or TPI suggests. The practical rule is simple: identify the thread specification of the component before selecting a fastener, and match it exactly. If you are unsure what thread a tapped hole uses, identify it with a pitch gauge before inserting any fastener — not after. The cost of proper identification is a few minutes; the cost of a stripped tapped hole in a machine casting or a structural member can be substantial. Near-Misses That Cause Real Problems The most damaging fastener errors occur not when threads are obviously different, but when they are close enough that a fastener will start threading before seizing. Several metric and imperial combinations are near-misses — similar enough in diameter that someone in a hurry will try them, and similar enough in pitch that the nut advances a few turns before locking solid. The table below shows the combinations most frequently encountered in Australian workshops: Metric Imperial near-miss Diameter gap Pitch difference What happens M6 × 1.0 1/4"-20 UNC 6.0 mm vs 6.35 mm (0.35 mm) 1.0 mm vs 1.270 mm Cross-threads immediately. Damage to nut thread within 1–2 turns. M8 × 1.25 5/16"-18 UNC 8.0 mm vs 7.94 mm (0.06 mm) 1.25 mm vs 1.411 mm Closest diameter match. Nut advances 2–4 turns before seizing. High risk of stripped thread in tapped hole. M10 × 1.5 3/8"-16 UNC 10.0 mm vs 9.525 mm (0.475 mm) 1.5 mm vs 1.588 mm Appears to thread, locks tight. No clamping force; will fail under load. M12 × 1.75 1/2"-13 UNC 12.0 mm vs 12.7 mm (0.7 mm) 1.75 mm vs 1.954 mm Diameter gap is larger but people still attempt. Do not substitute. M6 × 1.0 1/4" BSW (20 TPI) 6.0 mm vs 6.35 mm 1.0 mm vs 1.270 mm + 55° vs 60° Thread angle mismatch prevents correct engagement even if pitch were close. M8 × 1.25 5/16" BSW (18 TPI) 8.0 mm vs 7.94 mm (0.06 mm) 1.25 mm vs 1.411 mm + 55° vs 60° The most dangerous Whitworth near-miss — diameter almost identical. Profile incompatibility causes hidden thread damage. The M8/5/16" combination — in both UNC and BSW variants — is the most commonly encountered near-miss in Australian workshops. The diameter difference is under 0.1 mm, well within the range where threads will engage before the mismatch becomes apparent. The nut or bolt advances far enough to make the assembler think the connection is made, then seizes or strips the parent thread without warning. The rule to follow, without exception: if a fastener does not run on smoothly by hand for the first several turns with no resistance, stop. A fastener that requires force to start threading is almost certainly the wrong system or the wrong pitch. Apply tool torque only once the fastener has threaded cleanly by hand for at least five to six turns. Strength Grade Systems Compared Metric and imperial fasteners use different grade marking systems, and grade values from one system cannot be directly substituted for another. Understanding both systems is essential when replacing fasteners on mixed-standard equipment. Metric grade markings appear as two numbers separated by a point, stamped on the bolt head — 4.6, 8.8, 10.9, 12.9. The first number multiplied by 100 gives the minimum ultimate tensile strength (UTS) in MPa. The product of the two numbers, divided by 10, gives the yield strength in MPa. So an 8.8 bolt has a UTS of 800 MPa and a yield strength of 640 MPa (80% of 800). Metric grade UTS (MPa) Yield (MPa) Common use 4.6 400 240 General hardware, non-structural 5.8 500 400 Light structural, general engineering 8.8 800 640 Standard engineering/structural — the most common high-tensile metric grade 10.9 1000 900 Heavy structural, socket head cap screws, clamped connections 12.9 1200 1080 Highest standard grade — critical joints, socket head cap screws in precision machinery SAE/ASTM grade markings for imperial fasteners use radial lines on the bolt head. No marks indicates Grade 2 (low strength). Three evenly spaced radial lines indicate Grade 5 (medium — UTS approximately 827 MPa for 3/4" and under). Six radial lines indicate Grade 8 (high strength — UTS approximately 1034 MPa). Grade 5 is broadly comparable to metric 8.8 in tensile strength, and Grade 8 falls between metric 10.9 and 12.9 — but the testing standards differ and direct substitution without engineering sign-off is not appropriate on structural or safety-critical applications. BSW and BSF grade markings were not originally standardised in the same way as modern metric or SAE grades. Historical British standards specified material and heat treatment rather than a numerical head marking system. Modern Whitworth replacement fasteners produced for maintenance supply are often manufactured to ISO metric strength levels and marked accordingly — an 8.8-grade BSW bolt is threaded to BSW specification but manufactured to ISO 8.8 tensile requirements. Confirm grade requirements with your supplier when replacing structural BSW fasteners. For a full breakdown of metric bolt head markings and grade identification, see the AIMS Bolt Grade Chart. For tightening torques across all metric grades, see the AIMS Metric Bolt Torque Chart. What Equipment in Australia Uses Imperial Fasteners Knowing where to expect imperial threads prevents wasted time and avoidable damage. The categories below cover the most common sources of imperial fasteners in Australian maintenance workshops. US-manufactured heavy plant and earthmoving equipment is the primary source of UNC fasteners in Australian industry. Caterpillar, John Deere, Case, Bobcat, Terex, and most American-brand construction, earthmoving, and agricultural machinery use UNC and UNF throughout — engine ancillaries, structural frames, hydraulic mounting brackets, and access panels. This equipment is purchased new in Australia today and is in service on farms, mine sites, and construction projects across the country. If you maintain US OEM equipment, UNC in common sizes (1/4" through 3/4") should be standard stock. American-designed engines — Detroit Diesel, older Cummins, Continental, Lycoming, and most US-designed diesel and petrol engines — use SAE threads in the block, head, ancillaries, and valve train. Replacement fasteners on these engines must match the original specification. Mixing metric replacements into an imperial engine block will damage the block thread. Pre-metrication British and Australian machinery — equipment manufactured in Australia or the UK before the mid-1970s will typically carry BSW threads throughout. This includes older industrial lathes, milling machines, presses, compressors, and general workshop machinery still operating in tool rooms and maintenance shops, as well as older British-built vehicles and agricultural equipment. Classic British motorcycles — Triumph, BSA, Norton — and classic Land Rover models (Series I, II, IIA) are predominantly BSW/BSF. Mining and heavy industry presents a mixed environment. Australian-built process equipment installed from the 1980s onward is typically metric. US and Canadian OEM equipment brought in for mine development, drilling, and materials handling is typically UNC/UNF. It is common for a single machine to have metric fasteners on locally fabricated components and imperial fasteners on OEM components from the US manufacturer. Mixed environments require more discipline in thread identification, not less. Some hydraulic and pneumatic systems on otherwise-metric Australian machinery use imperial fittings — specifically JIC (37° flare), NPT (National Pipe Taper), and SAE straight thread port connections are common on hydraulic systems even where the machine structure is fully metric. These are pipe and fitting threads, not fastener threads, but they require imperial identification and imperial tooling to service correctly. Aerospace and defence maintenance in Australia involves both metric (European-origin aircraft) and UNF (US-origin aircraft and defence platforms) threaded fasteners. UNF is preferred in aviation for its vibration resistance and higher strength at a given diameter. Aerospace fasteners are also subject to specific material and certification requirements beyond standard commercial grades. How to Identify an Unknown Thread Working on an unfamiliar machine without documentation is a common scenario in maintenance. The following approach identifies thread specification reliably without guesswork. Step 1 — Measure the diameter. Use a vernier calliper to measure the outer diameter of the bolt or the minor diameter of the tapped hole. Metric bolt diameters will measure close to whole millimetre values: 8.0 mm, 10.0 mm, 12.0 mm. Imperial bolt diameters will measure close to inch fractions: 9.525 mm (3/8"), 12.7 mm (1/2"), 15.875 mm (5/8"). This narrows the candidates to a short list. Step 2 — Use a thread pitch gauge. A thread pitch gauge is a set of profiled blades, each calibrated to a specific pitch. Place blades against the thread form until one sits flush with no gap at the crests or roots and no rocking. Metric pitch gauge blades are labelled in millimetres of pitch. UN pitch gauge blades are labelled in TPI. Whitworth pitch gauge blades are also labelled in TPI but have a 55° profile — if the Whitworth blade seats correctly where the UN blade does not, the thread is BSW or BSF. This three-way comparison reliably distinguishes all four common thread standards. Step 3 — Cross-reference with the pitch tables. Once you have diameter and pitch (or TPI), cross-reference against the tables in this article or the AIMS Fastener Reference Chart to confirm the thread designation. Use a go/no-go gauge for tapped holes. A go/no-go gauge is binary — the "go" end must pass freely through the full depth of the tapped hole, and the "no-go" end must not enter. Go/no-go gauges are the most reliable method for confirming thread specification in production and quality control environments, and for detecting thread damage in a hole that has been previously used. Bring a sample to AIMS. If you cannot identify a thread from the equipment itself, bring a fastener sample to AIMS. We carry thread gauges across metric, UNC, UNF, BSW, and BSF and can identify threads on the spot. This is faster and less costly than attempting identification by trial and error on the machine — particularly where the tapped hole is in a casting, cylinder head, or other component where thread damage would be expensive to repair. When to Keep Imperial Fasteners in Stock For a well-run maintenance workshop, the decision about what imperial stock to carry should follow the equipment you service, not general habit. Maintaining a stock of every thread system in every size wastes space and money and increases the risk of the wrong fastener being selected under time pressure. If you maintain US-manufactured plant equipment, carry UNC in the sizes most commonly used on that equipment — typically 1/4" through 3/4" in Grade 5 and Grade 8. Grade 5 is the most common working grade on US OEM equipment; Grade 8 for critical joints. Do not substitute metric 8.8 for Grade 5 even when the tensile strength appears comparable — the thread pitch is incompatible, and cross-referencing grades across standards for structural applications requires engineering review. If you service older British machinery, classic vehicles, or legacy plant, carry BSW in the sizes that recur on your equipment. BSF can typically be sourced on demand unless you regularly work on specific models that require it. Keep BSW and UNC in separate, clearly labelled sections of your fastener storage — their similar TPI values (at some diameters) and nearly identical diameters make them a mix-up risk. Storage discipline is not optional. Metric and imperial fasteners of similar diameter look identical to the eye at normal working distances. A mixed bin is a liability. Labelled compartments, colour-coded containers, or physically separate storage for each thread system eliminates the problem at the source. The time spent on bin organisation is recovered many times over by the time not spent dealing with stripped threads. For one-off requirements, unusual sizes, or threads encountered only occasionally, AIMS can supply across all systems without requiring you to hold slow-moving stock. For critical or structural applications involving unusual thread specifications, AIMS has also arranged custom and special fasteners to customer requirement — contact our team to discuss. AIMS Industrial Fastener Range AIMS stocks fasteners across all thread systems commonly encountered in Australian industry — metric, UNC, UNF, BSW, and BSF — in standard industrial grades and materials. The range covers bolts, nuts, screws, washers, allthread (threaded rod, also known as Brooker rod), and specialist fastener types including security fasteners and thread inserts. Metric fasteners cover M5 through M36 in standard grades (4.6 for general hardware, 8.8 for structural and engineering applications). Stainless steel 316 is available for corrosive environments including marine, food processing, and chemical applications. Browse the AIMS bolts range, nuts, screws, and washers. UNC and UNF fasteners are stocked across common sizes used on US-manufactured equipment — 1/4" through 3/4" in Grade 5 and Grade 8 for most applications. UNF is available alongside UNC in standard sizes. Both are available for immediate dispatch on standard lines. BSW fasteners are stocked in the sizes most frequently required for maintenance of older British and Australian machinery — the sizes you will encounter most often on older plant, classic vehicles, and legacy industrial equipment. AIMS also carries BSF in key sizes; less common BSF sizes can be sourced on request. BSW and BSF are not always readily available from general hardware suppliers, so AIMS's stocking of the Whitworth range is a practical advantage for workshops maintaining older equipment. Allthread and threaded rod is available in metric and imperial specifications, in common diameters and standard lengths. Allthread is used for threaded anchors, through-bolt assemblies, suspension systems, and custom fastening solutions where standard bolt lengths are insufficient. Browse the AIMS allthread range. For full coverage of allthread grades, sizes, the nut trick for cutting, joining with coupling nuts and acme thread, see our Threaded Rod Guide. Specialist fastener products include security fasteners, thread inserts (Recoil and standard), washers across metric and imperial, rivets, and anchors. For the full range, see AIMS Industrial fasteners — over 1,400 products across all fastener categories. Custom and special fasteners — non-standard lengths, unusual grades, specific materials, or thread specifications outside the standard range — can be arranged through AIMS. Contact our team via the AIMS contact page or call (02) 9773 0122 to discuss requirements. For screw head types and drive patterns across both metric and imperial fasteners, see the AIMS Screw Head Types Guide. For socket head cap screws specifically, see the Socket Head Cap Screw Guide For metric pin fasteners — including roll pins (spring pins, sellock pins) in DIN 1481 sizing — see the Roll Pin Guide. For the wider fastener orientation across thread systems, grades and head types, see our Fastener Quick Guide. Frequently Asked Questions Are metric and imperial fasteners interchangeable? No. Metric and imperial fasteners are not interchangeable. Even where diameters appear similar, thread pitches differ, and Whitworth threads (BSW/BSF) use a 55° flank angle versus 60° for metric ISO and Unified threads. Attempting to mix systems will cross-thread or strip the fastener, often with no visible warning until the joint fails. What does M10 × 1.5 mean on a metric bolt? M10 × 1.5 is an ISO metric designation. 'M10' means the nominal outer diameter is 10 mm. '1.5' is the thread pitch — the distance in millimetres between adjacent thread crests. When a length follows (e.g. M10 × 1.5 × 40), the final number is the bolt length in millimetres. If pitch is not stated, coarse pitch is assumed by convention. What is the difference between UNC and UNF? UNC (Unified National Coarse) and UNF (Unified National Fine) both use a 60° thread angle. UNC has fewer threads per inch — it assembles faster and tolerates contamination better. UNF has more threads per inch, providing finer adjustment and better vibration resistance. Common UNC: 3/8"-16. Common UNF: 3/8"-24. They are not interchangeable even at the same nominal diameter. Is 3/8" the same as M10? No. 3/8" is 9.525 mm in diameter; M10 is 10.0 mm. More importantly, their pitches differ: M10 coarse is 1.5 mm pitch and 3/8"-16 UNC is approximately 1.588 mm pitch. An M10 nut will not correctly engage a 3/8" UNC bolt. This is one of the most common near-miss combinations in Australian workshops — the diameter similarity makes it tempting to try, and the pitch mismatch ensures thread damage results. What does 8.8 mean on a metric bolt? 8.8 is the ISO property class for a medium-high strength metric fastener. The first digit (8) multiplied by 100 gives the minimum UTS in MPa: 800 MPa. The second digit (8) indicates the yield-to-UTS ratio as a percentage: 80%, giving a yield strength of 640 MPa. 8.8 is the most common high-tensile metric grade for general engineering and structural applications in Australia. Which fastener system is standard in Australia? Metric (ISO) is the Australian standard for fasteners under AS 1110, AS 1111, and related standards. All new engineering, construction, and manufacturing in Australia specifies metric. However, UNC is common on US-manufactured equipment imported into Australia, and BSW/BSF appears on pre-metrication British and Australian machinery. All three systems are regularly encountered in maintenance environments. What is BSW? BSW stands for British Standard Whitworth — developed by Sir Joseph Whitworth in the 1840s. BSW uses a 55° thread flank angle (versus 60° for metric and UN threads), with diameter specified in inches and pitch in threads per inch. It is found on older British and Australian machinery manufactured before metrication, classic British vehicles, and some legacy industrial equipment. BSW is the coarse pitch thread in the Whitworth family. What is the difference between BSW and BSF? Both BSW and BSF are Whitworth threads with a 55° flank angle. BSW (British Standard Whitworth) is the coarse pitch thread. BSF (British Standard Fine) uses a finer pitch — more threads per inch at the same diameter — for applications requiring greater clamping force or vibration resistance. BSW nuts and BSF bolts of the same nominal diameter are not interchangeable. Is BSP the same as BSW? No. Both share a 55° thread angle but are completely different standards. BSP (British Standard Pipe) is a pipe and fitting thread for hydraulic, pneumatic, and plumbing connections — not a fastener thread. BSP comes in parallel (BSPP) and tapered (BSPT) forms. The pitch tables, diameter designations, and sealing arrangements are entirely different from BSW. Never substitute BSP fittings for BSW fasteners or vice versa. How do I tell if a bolt is metric or imperial? Measure the outer diameter with a vernier calliper. Metric diameters will be close to a whole millimetre (8.0 mm, 10.0 mm, 12.0 mm). Imperial diameters will be close to inch fractions (9.525 mm for 3/8", 12.7 mm for 1/2"). Then use a thread pitch gauge to confirm pitch — metric blades read in mm, UN blades in TPI, Whitworth blades in TPI with 55° profile. If the Whitworth blade seats where the UN blade does not, the fastener is BSW or BSF. Can I use an M10 nut on a 3/8" bolt? No. M10 and 3/8" are close in diameter but their thread pitches are different. An M10 nut started on a 3/8"-16 UNC bolt will initially appear to thread, then seize and strip the nut thread within a few turns. Always match thread system, not approximate diameter. What is allthread or Brooker rod? Allthread — also called threaded rod or Brooker rod — is a length of bar stock threaded continuously along its full length, with no unthreaded shank. It is used in through-bolt assemblies, anchor bolt applications, suspension systems, and custom fastening solutions where standard bolt lengths are insufficient. Allthread is available in metric and imperial thread specifications and in materials including mild steel, high tensile, and stainless steel. What US equipment in Australia uses UNC fasteners? Most US-manufactured heavy plant and machinery uses UNC throughout — Caterpillar, John Deere, Case, Bobcat, Terex, and similar brands. US-designed diesel engines (Detroit Diesel, older Cummins) also use SAE/UNC threads. If you maintain American OEM equipment, carry UNC in common sizes (1/4" through 3/4") in Grade 5 and Grade 8 as standard stock. Why can't I just use the closest metric bolt to the imperial size I need? Because thread compatibility requires matching diameter, pitch, AND — for Whitworth threads — flank angle. Diameter proximity is not sufficient. A metric fastener of similar diameter to an imperial one has a different pitch, meaning threads will not engage correctly. In the best case it will cross-thread immediately; in the worst case it will appear to hold under hand tightening before stripping or failing under load. Always match thread specification exactly. Does AIMS stock BSW and other imperial fasteners? Yes. AIMS Industrial stocks UNC, UNF, BSW, and BSF alongside a full metric range. UNC and BSW are stocked in common sizes for immediate supply. UNF and BSF are available across the range, with BSF in more limited stock. Allthread is available in metric and imperial. Custom and special fasteners — unusual lengths, grades, materials, or thread specifications — can also be arranged. Call (02) 9773 0122 or contact AIMS to discuss your requirements. Pair this with our Tap Types guide — the spiral point vs spiral flute distinction matters more than most tradies realise. People Also Ask — Metric vs Imperial Fasteners in Australia Q: Which fastener system is standard in Australia — metric or imperial? Australia uses metric as the standard system for new construction, manufacturing, and engineering. However, imperial fasteners remain in service on equipment manufactured before Australia's metrication, and on imported equipment from the United States, which remains predominantly imperial. Q: How is a metric fastener specified? A metric fastener is specified by thread diameter in millimetres, thread pitch in millimetres per thread, and the required length. For example, M8 × 1.25 × 30 describes a bolt with an 8mm diameter, a standard coarse pitch of 1.25mm, and a 30mm body length. Q: Are metric and imperial fasteners interchangeable? Metric and imperial fasteners are not interchangeable — the thread forms, pitches, and dimensions are different. Forcing an imperial fastener into a metric hole, or vice versa, will cross-thread or strip the mating thread. Correct identification before replacement is essential. Q: What are the main imperial thread standards encountered in Australia? The main imperial thread types encountered in Australia are UNC (Unified National Coarse) and UNF (Unified National Fine) from American-origin equipment, and BSW (British Standard Whitworth) and BSF (British Standard Fine) on older British-origin machinery. BSP is the separate British Standard Pipe thread used in plumbing and pneumatic fittings. Q: What is the difference between metric coarse and metric fine threads? Metric coarse threads have a larger pitch (fewer threads per unit length) and are the standard choice for most general fastening applications. Metric fine threads have a smaller pitch and are used where greater resistance to loosening under vibration is needed, or where precise axial adjustment is required. Need metric thread forming taps? Browse the AIMS range at metric thread forming taps.How do I measure the thread pitch to tell metric from imperial? Use a thread pitch gauge: a metric blade seats cleanly in a metric thread and reads the pitch in millimetres (crest to crest), while an imperial blade reads threads per inch (TPI). If a metric blade rocks and an imperial one sits flush, the thread is imperial. Confirm the diameter as well, since some sizes are close. See our thread standards guide. Do metric and imperial bolts use different spanner sizes? Yes — a metric bolt takes a metric spanner sized to its hex head (an M10 head is 17mm across the flats), while an imperial bolt takes an AF (across-flats) spanner in inches. The head size doesn't match the thread size in either system, and a metric spanner won't fit an imperial head cleanly. Keep both metric and AF spanner sets if you work on mixed equipment. See the fasteners range. How do metric and imperial bolt grade markings differ? On a metric bolt the strength is a property-class number stamped on the head (8.8, 10.9, 12.9); on an imperial bolt, SAE grade is shown by radial lines on the head (three lines for Grade 5, six for Grade 8). The two marking systems aren't interchangeable, so read the head marks in the right system. For the full decode see our high-tensile bolt identification guide.
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Stripped Thread Repair Guide: Helicoil, Recoil & Inserts
What Is a Stripped Thread? A stripped thread is a threaded hole — or external thread — where the thread profile has been damaged to the point that the original fastener no longer engages reliably. The thread crests have been crushed, sheared, or pulled out; the helical groove that should grip the bolt is now smooth or partially intact at best. The bolt either spins freely without grabbing, pulls out under hand pressure, or strips deeper as you try to tighten it. The joint cannot develop clamping force. Stripped threads happen for predictable reasons: Over-torquing — applying torque beyond the parent thread's yield point, particularly in soft parent materials (aluminium, magnesium, plastic). The most common cause across AU automotive and industrial work. Cross-threading — starting the bolt at an angle and forcing it. Damages the lead thread and propagates as the bolt is tightened. Repeated cycling on a soft parent — aluminium engine blocks with spark plug threads removed and reinstalled hundreds of times eventually wear out the parent thread. Corrosion damage — outdoor and marine threads where the parent metal corrodes and the thread profile degrades. Wrong-size fastener — the wrong thread pitch or diameter forced into a hole. Heat damage — repeated thermal cycling or localised overheating annealing the parent material. Thread repair is appropriate when the parent component is expensive or impractical to replace — engine blocks, gearbox housings, machine castings, marine outboard blocks, structural plate. It is not always the right answer; sometimes drilling the hole oversize and using a larger bolt, or replacing the parent component entirely, is faster and cheaper. This guide covers when to repair, what to use, and how to do it. The full AIMS thread repair range — Recoil wire inserts and keyserts (the AU-stocked brand), Champion budget kits, and individual taps and inserts — is at the Recoil collection at AIMS. Recoil — The Australian Thread Insert Brand Recoil is the AU-founded thread insert brand stocked at AIMS Industrial. The Recoil product range covers the two main thread insert technologies in industrial supply: Recoil wire inserts (helical inserts) — the diamond-cross-section stainless wire wound into a helical coil that screws into a tapped oversize hole. Dimensionally compatible with Helicoil. The general-purpose option for most AU repair work. Recoil Keyserts (key-locking inserts) — solid threaded bushings with locking keys driven into the parent material. Mechanically locked into the parent thread, used where vibration resistance and fail-proof installation are critical. Recoil's Australian heritage is worth knowing. The Recoil brand originated in Australia and remains the dominant AU industrial thread insert brand at AIMS and through specialist tool suppliers. The Recoil product line is dimensionally compatible with international Helicoil and Heli-Coil products at most sizes — the inserts, taps, and installation tools interchange across most metric and imperial threads. For most AU thread repair work in this guide we will refer to Recoil and Helicoil together where they are functionally interchangeable, and call out the specific differences where they matter. If you are working off an older purchase order or service manual, our Recoil 2007 → 2013 → 2023 part number cross-reference translates legacy codes to current RC kit numbers. Recoil Wire Inserts — How They Work and When to Use The wire insert — Recoil's flagship product, equivalent to Helicoil and Heli-Coil — is the most widely used thread repair technology globally. It is supplied as a tightly-wound stainless steel coil with a diamond cross-section. Each turn of the coil forms a thread profile when installed in a properly tapped oversize hole. How the wire insert installs The damaged threaded hole is drilled out to the insert's specific tap drill size, then tapped using a special oversize tap (the Recoil/Helicoil tap is larger than a standard tap of the same nominal thread because it cuts the thread that will receive the insert). The insert is wound into the new tapped thread using a dedicated installation tool. The diamond cross-section springs into the parent thread under tension, locking the coil in place. The driving tang at the bottom of the coil is then snapped off using a punch and the tang break-off tool — the bolt cannot enter the insert until the tang is removed. The repaired hole now accepts the original-size bolt as if the parent thread had never been damaged. Why wire inserts are stronger than the original thread A counterintuitive engineering point. A properly installed wire insert distributes clamping load across the wire's full coil contact with the parent thread — significantly more bearing area than the original tapped thread provided. The wire's spring action also accommodates minor parent thread imperfections that would have weakened a standard thread. A correctly-installed Recoil or Helicoil insert is mechanically stronger than the original thread, not just equivalent. This is why thread inserts are used on aluminium aerospace components and engine blocks where the OE thread design is the weak link. When to choose wire inserts General thread repair on engine blocks, machine castings, gearbox housings Aluminium parent material where the soft thread strips repeatedly Manifold studs, head studs, mounting points Cost-sensitive repairs where high-volume insertion is needed Threads that will not be cycled often (assembly threads rather than service threads) Recoil Keyserts — Key-Locking Inserts for Vibration-Critical Applications The Recoil Keysert (also called a key-locking insert or Keensert in US trade language) is a solid threaded bushing — not a wound coil. The Keysert has external threads on the body that screw into a tapped oversize hole, with locking keys (typically four small keys around the perimeter) that are driven down into the parent material once the bushing is fully installed. The locking keys mechanically prevent the insert from rotating, even under vibration. How Keyserts differ from wire inserts Feature Recoil wire insert (Helicoil) Recoil Keysert (key-locking) Construction Wound stainless wire coil Solid threaded bushing with locking keys Locking mechanism Spring tension against parent thread Mechanical keys driven into parent material Vibration resistance Good Excellent — fail-proof Removal Possible (drill out tang then unscrew) Difficult — must drill out the locking keys Wall thickness required in parent Less material needed More parent material needed for keys Cost per insert Lower Higher Best for General repair, soft parents, engine blocks Aerospace, vibration-critical, fail-proof joints Recoil Keyserts are specified in aerospace, defence, motorsport, and any application where insert rotation-loosening would be catastrophic. The mechanical keys make the insert genuinely permanent — drilling the keys out is the only removal method, which is itself an installation reliability indicator. When to choose Keyserts Aerospace and defence applications where fail-proof matters Motorsport and high-vibration machinery Any joint where insert rotation under vibration would cause catastrophic failure Critical structural mounting points Where the parent material is sufficient to accept the locking keys TimeSert — The Solid Bushing Alternative TimeSert is a different thread repair technology — a solid one-piece threaded bushing manufactured to a specific bolt size. Unlike a wire insert, TimeSert installs as a single rigid component. The defining feature is the flared top: a small lip at the top of the bushing sits in a counterbore prepared in the parent material, physically preventing the insert from being driven too deep — and critically, preventing it from dropping into engine cylinders or other internal cavities. TimeSert installation requires: Drilling the parent hole to TimeSert's specific drill size (smaller than a Helicoil/Recoil tap drill — TimeSert needs less material removed) Counterboring the top of the hole to accept the flared head Tapping the hole to the TimeSert thread spec Threading the TimeSert in until the flare seats in the counterbore Using TimeSert's installation tool to cold-roll-expand the bottom of the bushing — this locks the insert into the parent thread by cold deformation The cold-roll bottom expansion is what locks the TimeSert in place. There is no tang to break off, no spring tension, no locking keys — just a permanently expanded bottom that grips the parent thread mechanically. When to choose TimeSert Spark plug threads — the AU automotive standard. Spark plug threads cycle every service interval; the rigid TimeSert handles repeated removal and reinstallation better than a wire insert. Drain plugs and oil bolt holes — service threads removed and reinstalled regularly Engine cylinder threads where insert drop-in is unacceptable — TimeSert's flare prevents the insert from falling into the cylinder during installation. This is the safety reason TimeSert dominates aluminium head spark plug repair. Cover bolt threads — covers that come off and back on multiple times in service The trade-off is cost — TimeSert kits cost considerably more than Recoil/Helicoil kits, and TimeSert requires its specific tooling for each thread size (no interchange with Helicoil tools). For one-off repairs where the application doesn't strictly need TimeSert, Recoil/Helicoil is the cost-effective choice. Helicoil vs Recoil — Same Product, Different Brand This is the disambiguation most AU industrial buyers don't realise they need. Helicoil and Recoil are essentially the same product — wire thread inserts to similar dimensional standards — manufactured by different companies. The terms are used interchangeably in AU trade language much as "Biro" became the generic term for ballpoint pens in Australia. Aspect Helicoil Recoil Origin US (Heli-Coil Corporation, now Stanley Black & Decker) AU heritage, now part of Stanley Black & Decker Wire insert dimensions Industry standard helical wire Industry standard helical wire — interchangeable Tap drill sizes Same as Recoil Same as Helicoil Tap dimensions Special oversize tap, brand-specific Special oversize tap, brand-specific Installation tool Brand-specific tool Brand-specific tool — but works with Helicoil inserts AU stock at AIMS Not the primary brand Primary brand — AU stocking advantage For AU buyers: when a Helicoil is specified on an OE workshop manual or a parts catalogue, a Recoil insert of the same nominal size will fit and perform identically. The exceptions are the installation tap and the installation tool — these are brand-specific and not interchangeable. If you have a Helicoil kit's tools, use Helicoil inserts; if you have a Recoil kit's tools, use Recoil inserts. Steel vs Stainless Inserts — Interchangeability and Galvanic Corrosion Recoil and Helicoil inserts are stocked in two main material grades: stainless steel (304 or 316) and carbon steel (typically phosphor bronze or coated steel for some applications). The question that comes up regularly: can you mix stainless inserts with steel bolts in steel parents, or vice versa? The short answer: generally yes for dry indoor and most ambient applications, but mixing materials in wet, salt-laden, or chemical environments creates galvanic corrosion risk. The mechanical question Insert material and bolt material do not mechanically need to match. The insert provides the thread; the bolt is the fastener. The joint's clamping load is determined by the bolt grade (e.g. Class 8.8 or 12.9), not by the insert material. A stainless insert with a Class 12.9 carbon steel bolt achieves the bolt's full clamping capacity provided the insert and parent thread are correctly sized. The corrosion question Galvanic corrosion occurs when two dissimilar metals are in electrical contact in the presence of an electrolyte (water, particularly salt water). The less noble metal corrodes preferentially. The combinations that matter for thread inserts: Insert Bolt Parent material Indoor / dry use Wet / coastal / marine use Stainless Stainless Stainless ✓ Fully matched ✓ Specify 316 in marine Stainless Carbon steel Stainless or steel ✓ Generally OK ⚠️ Carbon steel bolt corrodes preferentially Stainless Stainless Aluminium ✓ Generally OK ⚠️ Aluminium parent corrodes preferentially in salt Carbon steel Carbon steel Aluminium ✓ Generally OK ⚠️ Aluminium parent corrodes; use anti-seize Carbon steel Stainless Any ✓ Generally OK ⚠️ Carbon steel insert corrodes preferentially Practical AU rule: For indoor industrial, dry environments, and general workshop repair — interchange freely between stainless and carbon steel inserts and bolts. For coastal Australian sites within 1 km of the surf, marine applications, swimming pool fittings, food processing brines, and chemical environments — match all three components (insert, bolt, parent) to the same material family or specify all stainless 316. Use anti-seize compound on threads to slow any galvanic action where mixed materials are unavoidable. Step-by-Step Thread Repair with Recoil/Helicoil The four-step procedure works across all wire-insert systems (Recoil, Helicoil, Heli-Coil, KATO). Specific tap drill sizes and tap dimensions vary by brand and insert size — refer to the kit instructions. Step 1 — Drill the damaged thread oversize Use the drill bit supplied with the kit (or specified in the brand's drill chart). The drill removes the existing damaged thread and creates a clean cylindrical hole sized to accept the special oversize tap. Drill straight — perpendicularity matters. Apply cutting oil. Use a drill press or a guide where accuracy is critical. Step 2 — Tap the hole with the kit's special tap The kit-supplied tap is larger than a standard tap of the nominal bolt size. It is dimensioned specifically to cut the thread that will receive the insert. Apply cutting fluid liberally. Turn the tap clockwise to cut, then back off a quarter turn to break the chip — repeat throughout the cut. The quarter-turn back-off is non-negotiable; skip it and the tap will bind, the chip will jam, and the tap will break (sending you to the broken tap removal procedure). Continue until the tap has cut a full thread through the hole depth. Remove the tap, clear chips from the hole. Step 3 — Install the insert Load the insert onto the installation tool with the tang at the bottom. Wind the insert into the tapped hole, applying light downward pressure. Continue winding until the top of the insert is approximately 1/4 to 1/2 turn below the top surface of the parent material. This below-flush position is intentional and correct — the insert is not supposed to be flush with the surface. Reverse the installation tool to release torque. The insert expands slightly to lock against the new parent thread. Step 4 — Break off the tang Use the kit's tang break-off punch (a simple cylindrical punch). Insert the punch into the installed insert until it contacts the tang. Strike the punch sharply with a hammer. The tang shears off cleanly at the notched break point. Remove the broken tang from the hole. The repaired hole now accepts the original bolt size. Test fit the bolt to confirm the thread is clean and engaging properly. Practical buying tip: Budget for 25-50% extra inserts on any repair job. Some inserts will break or distort during installation, particularly if the tapped hole has minor imperfections or the installation tool is worn. Cheap kits' installation tools are the most common cause of insert damage during install — invest in a quality tool. Insert Size Selection — Drill, Tap and Insert Reference Recoil and Helicoil insert sizing follows a consistent pattern: the insert designation matches the original bolt size (e.g. M8 insert for M8 bolt repair), but the drill and tap are oversize to the original bolt thread. Bolt size Insert designation Drill size (mm) Tap (special) Insert lengths typically stocked M3 M3 insert 3.3 M3 STI tap 1.5d, 2d M4 M4 insert 4.3 M4 STI tap 1.5d, 2d M5 M5 insert 5.5 M5 STI tap 1.5d, 2d, 2.5d M6 M6 insert 6.3 M6 STI tap 1.5d, 2d, 2.5d, 3d M8 M8 insert 8.4 M8 STI tap 1.5d, 2d, 2.5d, 3d M10 M10 insert 10.4 M10 STI tap 1.5d, 2d, 2.5d, 3d M12 M12 insert 12.4 M12 STI tap 1.5d, 2d, 2.5d, 3d M14 M14 insert 14.5 M14 STI tap 1.5d, 2d, 3d M16 M16 insert 16.5 M16 STI tap 1.5d, 2d, 3d M20 M20 insert 20.5 M20 STI tap 1.5d, 2d, 3d M24 M24 insert 24.5 M24 STI tap 1.5d, 2d, 3d Insert length is given in multiples of the bolt diameter (d). 1.5d is the standard length for most general repair work; 2d and 2.5d are used where higher clamping load or extra thread engagement is needed; 3d is used for high-load critical applications, particularly in soft parent materials. For the matching tap selection, see our Tap & Die Guide — note that thread insert taps (STI taps) are different from standard taps and are not interchangeable with a standard tap & die set. Common Australian Applications Engine block thread repair The most common AU thread repair application. Aluminium head spark plug threads stripped from over-torquing or thread wear → TimeSert (anti-drop flare design preferred for cylinders). Engine block manifold studs, head bolts, and accessory mounts → Recoil/Helicoil (cost-effective, sufficient for assembly threads). Particularly common on motorcycles, older vehicles, and equipment with aluminium heads. Marine outboard motor repair Salt water corrosion damages aluminium outboard motor block threads — common on Mercury, Yamaha, Honda outboards. Stainless 316 inserts with stainless 316 bolts is the standard; carbon steel inserts will corrode and seize. Use anti-seize on installation. The exhaust manifold and cooling water gallery threads are the highest-frequency repair points. Industrial machinery and pump housings Cast iron pump bodies, machine castings, and gearbox housings with stripped threaded mounting holes. Recoil wire inserts handle the bulk of this work; Keyserts where vibration is a concern. Motorcycle and small-engine repair Aluminium crankcase covers, drain plugs, valve cover bolts, sprocket cover bolts. AU motorcycle workshops use Recoil/Helicoil for most repairs; TimeSert for spark plug threads where they cycle frequently. Agricultural and 4WD off-road Tractor PTO covers, implement mounting threads, differential cover bolts, hub stud threads. Cast iron and steel parents — Recoil wire inserts are the standard, with Keyserts for vibration-critical mountings. Aerospace and high-reliability applications Recoil Keyserts (key-locking inserts) — the aerospace standard. Used in airframe components, defence equipment, motorsport, and any application where insert rotation under vibration would cause catastrophic failure. When NOT to Use a Thread Insert — and the Loctite/JB Weld Debunk Drill out and use a larger bolt If the application allows a larger bolt size, drilling the damaged hole oversize and re-tapping to the next thread size (e.g. M8 stripped → drill out to M10) is faster, cheaper, and equally reliable. Common where the design is not size-specific and the bolt circle clearance allows. Saves the cost of a thread insert kit and the installation time. Replace the parent component Where the parent component is cheap or readily available, replacement is sometimes faster than repair. A stripped bolt hole in a $50 cover plate is not worth a $200 thread repair kit. Make the economic call: cost of repair (kit + labour + risk) vs cost of replacement. Loctite, JB Weld and "thread filler" — the debunk Loctite and JB Weld will NOT structurally repair a stripped thread. Loctite is a thread retaining adhesive designed to prevent vibration loosening on a sound thread — it has no structural strength to rebuild missing thread material. JB Weld and similar epoxies will fill a stripped hole and bond to the parent material, but the resulting joint is weaker than the original thread by an order of magnitude — entirely inadequate for any load-bearing or service-removable application. These products are useful for dust-tight cover bolts, plastic threads, and similar non-structural applications. They are not a substitute for a proper thread repair on any joint that needs to develop clamping load. If a forum or YouTube video suggests "just glue it" — that is appropriate only for non-structural applications. For any joint that will see vibration, load, or service removal, install a Recoil or TimeSert insert. The repair is permanent and reliable; the glue is a temporary fix that will fail. AIMS Industrial Thread Repair Range The full AIMS thread repair stock — Recoil inserts, Recoil tools, Champion budget kits, individual taps — is at the Recoil collection at AIMS. Recoil — the AU primary brand The Recoil range stocked at AIMS covers: Recoil wire inserts — stainless steel, M3 through M24 metric, 1.5d / 2d / 2.5d / 3d lengths, in individual packs and kit form Recoil Keyserts — key-locking inserts for vibration-critical applications, M5 through M16 Recoil installation tools — kit-specific installation tools, taps, drills, and tang break-off punches Recoil thread repair kits — complete thread repair sets in common sizes (M5 / M6 / M8 / M10 / M12) Champion — the budget alternative For occasional repair work and non-critical applications, the Champion CTRK14125 Thread Repair Stainless Steel Kit is a cost-effective option. The kit covers common sizes for general workshop repair. Budget Champion kits are appropriate for one-off jobs, hobby workshops, and non-critical applications. For serious workshop work with regular thread repair, the Recoil range is the better long-term investment. Companion product groups Stud Extractor Guide (Art 138) — when removing the broken fastener that damaged the thread Broken Tap Removal (Art 30) — when the tap breaks during the repair installation Tap & Die Guide (Art 41) — note that thread insert taps are different from standard taps Penetrating Oil Guide (Art 67) — for removing the original damaged fastener Thread Locking & Sealing Guide (Art 44) — Loctite has its place, but not for thread repair Bolt Grade Chart (Art 11) — matching bolt strength to repaired joint Frequently Asked Questions What is a stripped thread? A stripped thread is a threaded hole or external thread where the thread profile has been damaged so that the original fastener no longer engages reliably. The thread crests have been crushed, sheared, or pulled out, leaving a smooth or partially-intact surface that cannot develop clamping load. Common causes include over-torquing (especially in aluminium parent material), cross-threading, repeated cycling, corrosion damage, wrong-size fastener, and heat damage. Repair using a thread insert (Recoil, Helicoil, TimeSert) restores the original thread size in the damaged hole. What is the difference between Helicoil and Recoil? Helicoil and Recoil are essentially the same product — wire thread inserts to similar dimensional standards — manufactured by different companies (both now part of Stanley Black & Decker). The wire inserts themselves interchange dimensionally for most metric and imperial sizes. The exception is the installation tap and the installation tool — these are brand-specific. If you have a Helicoil kit's tools, use Helicoil inserts; if you have a Recoil kit's tools, use Recoil inserts. Recoil is the AU-founded brand and the primary stock at AIMS Industrial. How do you repair a stripped thread? The standard wire-insert repair procedure is: (1) drill the damaged hole oversize using the drill bit supplied with the thread repair kit; (2) tap the hole with the kit's special oversize tap (different from a standard tap); (3) wind the insert into the tapped hole using the installation tool until the insert sits 1/4 to 1/2 turn below the surface; (4) break off the driving tang at the bottom of the insert using the kit's punch. The repaired hole then accepts the original-size bolt as if the parent thread had never been damaged. For premium / high-cycle applications, a TimeSert solid bushing is installed similarly but with a counterbore and cold-roll-expansion finish. What is the difference between Helicoil and TimeSert? Helicoil (and Recoil) are wire inserts — a coiled diamond-cross-section wire that springs into place. TimeSert is a solid one-piece threaded bushing with a flared head that sits in a counterbore and a cold-rolled bottom that expands during installation. Wire inserts are cheaper, more widely stocked, and suitable for general repair. TimeSert costs more but tolerates repeated removal and reinstallation better, and the flared head physically prevents the insert from dropping into engine cylinders during installation. Use Helicoil/Recoil for assembly threads and one-off repair; use TimeSert for spark plug threads, drain plugs, and any thread that will be cycled frequently in service. Are thread inserts as strong as the original thread? Properly installed wire thread inserts are typically stronger than the original thread, not just equivalent. The wire insert distributes clamping load across the wire's full coil contact with the parent thread — significantly more bearing area than the original tapped thread provided. The wire's spring action also accommodates minor parent thread imperfections. This is why thread inserts are used as original equipment in aluminium aerospace components and aluminium engine blocks where the OE thread design is the weak link. Improper installation (insert too high, tang not removed, wrong tap drill size) is the only common reason inserts fail. Will Loctite fix a stripped thread? No. Loctite is a thread retaining adhesive designed to prevent vibration loosening on a sound thread — it has no structural strength to rebuild missing thread material. For non-structural cosmetic applications (dust covers, plastic threads, decorative bolts) Loctite may temporarily hold a stripped fastener, but for any joint that develops clamping load — engine bolts, structural fastenings, anything load-bearing — Loctite is not a thread repair. Install a Recoil, Helicoil, or TimeSert insert; the repair is permanent and reliable. Will JB Weld fix a stripped thread? No. JB Weld and similar epoxies will fill a stripped hole and bond to the parent material, but the resulting joint is weaker than the original thread by an order of magnitude — entirely inadequate for any load-bearing or service-removable application. Some YouTube tutorials and forum posts suggest using JB Weld for thread repair; this advice is appropriate only for non-structural plastic-cover bolts or decorative fastenings. For any structural or service thread, install a proper thread insert. What size drill bit do I need for an M8 Recoil insert? An M8 Recoil insert requires an 8.4 mm drill bit (some kits specify 8.5 mm — refer to your specific kit's instructions). This is larger than a standard M8 tap drill (6.8 mm) because the Recoil/Helicoil tap must cut a larger thread to receive the insert. The drill, special tap, and installation tool are all matched to the insert size and must be used together. Thread repair kits supply all three components — never substitute a standard M8 tap for the special insert tap; the threads will not match and the insert will not seat correctly. Can you reuse a thread insert? Wire inserts (Recoil, Helicoil) are not designed for reuse — once removed, the spring tension is lost and the insert no longer locks reliably. Replace any insert that has been removed. TimeSert solid bushings can be reused if removed carefully (the cold-roll bottom expansion does not reset to its installed dimension), but in practice replacement is the standard. Keyserts cannot be reused — the locking keys are deformed during installation and removal requires drilling them out, which destroys the insert. How do you remove a Helicoil or Recoil insert? Wire insert removal requires a Helicoil/Recoil extraction tool — a small tapered tool that bites into the top of the coil and unscrews it counterclockwise. If the original tang has been removed (as it should be after installation), the extraction tool grips the coil's top turn. If the insert is stuck or damaged, the removal procedure is to drill out the insert with a drill bit slightly smaller than the parent thread's tap drill — this destroys the insert but preserves the tapped hole, allowing a new insert to be installed. What is a Keysert and when do you use one? A Recoil Keysert (also called a key-locking insert or Keensert) is a solid threaded bushing with locking keys that are driven into the parent material after the bushing is installed. The mechanical keys prevent the insert from rotating under vibration — a fail-proof installation. Used in aerospace, defence, motorsport, and any vibration-critical application where wire insert rotation-loosening would cause catastrophic failure. Trade-offs: higher cost than wire inserts, more parent material required to accept the locking keys, removal requires drilling out the keys. For general repair, Recoil wire inserts are the cost-effective choice; for fail-proof critical applications, specify Keyserts. Can I just drill out the hole and use a larger bolt? Often yes. If the application allows a larger bolt size (the bolt circle clearance permits, the design is not size-specific, and the parent material is thick enough), drilling the damaged hole oversize and re-tapping to the next thread size (M8 → M10, M10 → M12) is faster, cheaper, and equally reliable. Saves the cost of a thread insert kit and the installation time. The decision factors: is the bolt size constrained by the design (mating component, OE specification, hole pattern), and is the parent material thick enough to accept a larger thread? If both are yes, drilling oversize is often the better answer. Can I mix steel and stainless inserts with different bolt materials? Mechanically yes — the insert provides the thread; the bolt is the fastener; clamping load is determined by bolt grade not insert material. For dry indoor and most ambient industrial applications, mixing stainless inserts with carbon steel bolts (or vice versa) is acceptable. The caveat is galvanic corrosion in wet, salt-laden, or chemical environments. In coastal AU sites within 1 km of surf, marine, swimming pool, food processing brine, and chemical environments, match all components (insert, bolt, parent) to the same material family or specify all stainless 316. Use anti-seize compound on threads to slow galvanic action where mixed materials are unavoidable. What's the best thread repair for engine blocks? Depends on the specific thread. For aluminium head spark plug threads (cycling every service interval, in cylinder so insert drop-in matters), TimeSert is the AU automotive standard — the flared head prevents the insert dropping into the cylinder during installation. For engine block manifold studs, head bolts, accessory mounts, and other assembly threads (installed once, rarely removed), Recoil/Helicoil wire inserts are the cost-effective choice. Marine outboard motor blocks (salt corrosion on aluminium) need stainless 316 inserts with stainless 316 bolts. Match the insert technology to the application's cycling and environmental demands. How tight should I install a thread insert? The insert itself does not have a specified torque — installation is done by hand using the kit's installation tool, winding the insert into the tapped hole until the top of the insert sits 1/4 to 1/2 turn below the parent surface. This below-flush position is intentional and correct. The bolt that is then installed into the repaired hole is torqued to the original bolt's specification — the insert does not change the bolt torque value. As a guide for AU automotive: M6 ≈ 8-10 Nm, M8 ≈ 20-25 Nm, M10 ≈ 40-50 Nm, M12 ≈ 65-80 Nm — always defer to the OE workshop manual where one is specified. Apply anti-seize on stainless threads before installing the bolt. Pair this with our Metric Bolt Size Guide for the thread pitch, AF dimension and grade options at every common size.
Read moreNyloc Nut Guide: DIN 985, Sizes, Temperature Limits & When to Use Self-Locking Nuts
What Is a Nyloc Nut? A Nyloc nut is a hex nut with a nylon insert (a coloured polymer ring) moulded into the top. As the nut is wound onto a bolt, the bolt's threads cut into the nylon, creating friction that resists vibration loosening. Once fitted, the nylon grips the thread and stops the nut backing off under normal vibration and shock loads. They're widely used in machinery, vehicles, marine applications and any assembly subject to vibration. Can a Nyloc nut be reused? Manufacturers recommend single-use. Each time the nut is wound on, the nylon insert deforms, and its locking force drops after the first removal. For safety-critical or vibration-prone joints, fit a new Nyloc nut every time you disassemble the joint. Nyloc Nut Sizes — Metric M3 to M30 Reference — Quick Reference The DIN 985 dimensional reference for the full standard metric range. All sizes use across-flats (AF) measurement equal to a standard hex nut of the same thread, so a 13 mm spanner fits an M8 Nyloc the same as an M8 hex nut. Thread size Across flats (mm) Approx height (mm) Stock at AIMS M3 5.5 4.0 Standard — Bremick zinc, stainless M4 7.0 5.0 Standard M5 8.0 6.0 Standard M6 10.0 7.5 Standard — extremely common M8 13.0 9.5 Standard — extremely common M10 17.0 11.5 Standard M12 19.0 14.0 Standard M14 22.0 16.0 Less common — to order M16 24.0 17.5 Standard M20 30.0 20.5 Heavy-duty — Bremick / Hobson M24 36.0 23.5 To order M30 46.0 28.0 Heavy-duty — Hobson What Is a Nyloc Nut? A Nyloc nut is a hex nut with a nylon (polyamide) ring fitted into the top of the body, designed to grip the threads of a bolt or threaded rod and prevent the joint from loosening under vibration. The nylon insert sits proud of the threaded portion of the nut — when the nut is wound onto a bolt, the bolt thread cuts into the nylon, creating friction that resists rotation in either direction. "Nyloc" is the original brand name (registered to Nyloc Corporation) but is now used generically across the Australian and global fastener industry to describe any hex nut with a nylon insert. You will see the same fastener under several names — all referring to the same product: Nyloc nut — dominant Australian trade term Nylock nut — common spelling variant; sometimes treated as a separate brand but functionally identical Nylon insert lock nut — engineering / technical term used on drawings and specs Stop nut or Elastic stop nut (ESL nut) — older trade language, mostly American origin, occasionally encountered on imported equipment Self-locking nut — generic engineering term that includes Nyloc plus all-metal lock-nut variants This guide covers DIN 985 (the low-profile metric standard, the most common AU stock) and DIN 982 (standard-height variant), the temperature ceiling above which Nyloc nuts stop locking, the reuse question, the materials and grades available at AIMS, the alternatives for applications where a Nyloc is the wrong choice, and the practical decision rules for choosing between them. The full AIMS Nyloc range — Bremick and Hobson stock in metric M4 to M30 plus imperial UNC and UNF, zinc-plated and 304/316 stainless — is available here. How a Nyloc Nut Works — The Prevailing Torque Mechanism A standard hex nut relies entirely on the friction between the bolt threads and the nut threads (plus the clamping load against the joint) to stay tight. Under vibration, that friction can cycle — the nut backs off slightly with each vibration pulse and over time loosens completely. This is the failure mode every wing nut, every standard nut on a vibrating motor, every bolt on a drum kit eventually finds. A Nyloc nut adds a second locking mechanism that does not depend on clamping load. The nylon insert sits in the unthreaded top section of the nut. When the bolt is wound through, the bolt thread engages the nut threads as normal — and then the bolt thread enters the nylon insert. The nylon is slightly under-sized relative to the bolt thread, so it deforms elastically as the thread passes through. The deformation grips the bolt thread, creating prevailing torque — friction that resists rotation independent of the clamping force. "Prevailing torque" simply means the torque required to turn the nut on the bolt before any clamping load develops. A standard hex nut has effectively zero prevailing torque — you can spin it freely down the thread. A Nyloc has prevailing torque from the moment the bolt thread engages the nylon. This is the engineered locking effect, and it is why Nyloc nuts stay tight even when the joint clamping force is reduced or temporarily lost. One practical consequence: installing a Nyloc requires more torque than a standard nut to wind it down. This is correct and intended — it is the prevailing torque doing its job. It is not a sign of cross-threading or a damaged nut. DIN 985 vs DIN 982 — Thin vs Standard Height This is the variant distinction most AU buyers do not realise exists. Two metric standards govern Nyloc nuts, with different overall heights but otherwise identical mechanics. Standard Profile Approx height (M8 example) Stock availability in AU DIN 985 / ISO 10511 Low-profile / thin ~8 mm Standard — dominant AU stock DIN 982 / ISO 7040 Standard / regular height ~10 mm Less common — special-order at most AU suppliers DIN 985 is what AU industrial buyers receive when ordering "M-something Nyloc" without specifying the standard. The thin profile saves height in tight-clearance assemblies and uses less material. DIN 982 has a taller body, slightly higher clamping capacity, and is preferred in heavy-duty or high-vibration applications where the longer thread engagement matters. For most general industrial work the two are functionally interchangeable; for engineered assemblies, follow the drawing specification. Imperial Nyloc nuts to ASME B18.16.6 (UNC and UNF threads) are also stocked at AIMS in 1/4" through 5/8" — common on imported American equipment, marine fittings, and agricultural hardware. Dimensional ratios are similar to DIN 985 — thin-profile is the AU default. Nyloc Nut Sizes — Metric M3 to M30 Reference The DIN 985 dimensional reference for the full standard metric range. All sizes use across-flats (AF) measurement equal to a standard hex nut of the same thread, so a 13 mm spanner fits an M8 Nyloc the same as an M8 hex nut. Thread size Across flats (mm) Approx height (mm) Stock at AIMS M3 5.5 4.0 Standard — Bremick zinc, stainless M4 7.0 5.0 Standard M5 8.0 6.0 Standard M6 10.0 7.5 Standard — extremely common M8 13.0 9.5 Standard — extremely common M10 17.0 11.5 Standard M12 19.0 14.0 Standard M14 22.0 16.0 Less common — to order M16 24.0 17.5 Standard M20 30.0 20.5 Heavy-duty — Bremick / Hobson M24 36.0 23.5 To order M30 46.0 28.0 Heavy-duty — Hobson The most commonly stocked sizes for AU general industrial work are M6, M8, M10, M12 and M16 — covering 80% of the assembly fastening Australian workshops encounter. Larger sizes (M20 through M30) appear in structural, agricultural, and heavy machinery applications. Smaller sizes (M3 through M5) in electronics, light fittings, and precision assembly. For matching bolt grades and the full thread reference, see our Bolt Grade Chart and Fastener Reference Chart. The 120°C Temperature Ceiling — Engineering Warning The single most overlooked specification on a Nyloc nut is the temperature limit of the nylon insert. This is a soft failure mode — the nut does not fall off catastrophically, it just stops working as a lock. Most users do not realise the lock effect has been lost until the joint loosens. Standard nylon (polyamide 6 or polyamide 6/6) used in Nyloc inserts retains its elastic properties between approximately −40°C and +120°C in service. Above 120°C the nylon softens, the prevailing torque grip on the bolt thread reduces, and at sustained service temperatures above 130–140°C the insert deforms permanently. The Nyloc becomes, mechanically, a regular hex nut with a now-useless plastic ring. Engineering warning — do not use a Nyloc near heat sources: Exhaust manifolds, flue connections, kiln components, oven internals, furnace flanges, near combustion chambers, near hot machinery casings, anywhere the joint regularly sees above 100°C in service. Apparent temperature is not the same as service temperature — a flange bolt next to an exhaust pipe can sit well above ambient. When in doubt, measure or err toward all-metal lock nuts (DIN 980, covered later in this guide). The temperature limit also caps Nyloc use in: Engine bay applications above the manifold — block-mounted brackets, turbo support brackets, heat-shield fixings Industrial process equipment — drying ovens, baking lines, polymer extruders Steam systems — flange connections on saturated steam piping above 100°C Foundry equipment — anywhere the working environment is hot ambient Welding fixtures — where the fastener can heat-soak through repeated welding cycles For these applications, switch to an all-metal lock nut (DIN 980 V Stover) — covered in the alternatives section below. Can You Reuse a Nyloc Nut? This is a question with two correct answers — depending on whether you are reading the manufacturer's data sheet or asking the tradesperson on the floor. The manufacturer position — single use Bremick, Hobson, Inox World and the major fastener brands universally publish "single-use" guidance for Nyloc nuts. The first time the bolt threads pass through the nylon insert, they cut a thread profile into the polymer. On removal, the nylon retains that profile but with reduced thickness and reduced elasticity. Each subsequent install/remove cycle reduces locking effectiveness further. By the third or fourth cycle, the insert provides minimal prevailing torque. The field position — depends on application criticality In real-world AU industrial practice, Nyloc reuse is common in non-critical applications. Workshop fixtures, hobby projects, light assembly that gets repeatedly pulled apart and reassembled — Nyloc nuts get reused. The locking effect degrades each cycle, but for low-vibration applications the residual friction is enough. Decision rule The deciding question is: what does failure cost? Application criticality Reuse policy Aviation, structural, lifting equipment, vehicle suspension, brakes Never reuse — replace every time Heavy machinery, vibrating equipment, vehicle drivetrain Replace whenever practical — reuse only in emergency Industrial assembly, machine guards, light vibration Reuse acceptable for one or two cycles; replace if locking feels reduced Workshop fixtures, hobby work, non-critical assembly Reuse common — replace when nylon visibly damaged A practical inspection check before reusing: wind the nut down the bolt by hand. If the threads engage and turn freely until the nylon hits the bolt, and the nylon then provides resistance with a clear "grip" feel, the locking effect is still functional. If the nut spins freely all the way down without resistance, the nylon is no longer effective — replace it. The other practical issue: nylon inserts are destroyed by abrasive grit, paint, rust, or thread debris before installation. A Nyloc that has been left in a dirty workshop drawer or installed on rusty threads will lock once, then fail. Clean threads are critical. Materials and Grades — Class 8, Class 10, 304 and 316 Stainless The Nyloc range at AIMS is matched to the bolt grades it pairs with. The grade rating refers to the strength of the nut body, not the locking effectiveness — the nylon insert is the same across all metal grades. Class 8 zinc-plated (DIN 985) The general-purpose AU industrial default. Class 8 carbon steel body matched to Grade 8.8 bolts, with zinc electroplate finish for moderate corrosion resistance. Suitable for indoor industrial assembly, light outdoor exposure under shelter, and most general fastening. Bremick and Hobson dominate AU stock at AIMS in this category. Class 10 zinc-plated (DIN 985) Higher-strength carbon steel matched to Grade 10.9 bolts. Used where the joint design specifies a Grade 10.9 bolt and the matching higher-strength nut is required. The nylon insert and locking mechanism are identical to the Class 8 version — the upgrade is in the metal body strength, not the locking effect. 304 (A2-70) stainless steel The general-purpose stainless option. Property Class A2-70 — approximately 700 MPa tensile. Suitable for outdoor work away from salt, food processing without chlorides, light marine (sheltered), pharmaceutical, and most outdoor applications where corrosion resistance matters more than maximum strength. 316 (A4-70) stainless steel The marine-grade option. Adds molybdenum for chloride resistance. Specify 316 for marine fittings, coastal industrial sites, swimming pool fittings, food processing brines, and chemical environments. Approximately 30% more expensive than 304. Stainless and Nyloc — galling note: Stainless threads can gall (cold-weld) when wound dry into matching stainless threads. This applies to the metal portion of the Nyloc but not the nylon insert. To prevent galling, apply a thread lubricant or anti-seize to the bolt threads before installation. The nylon portion does not need lubrication — the prevailing torque mechanism still works as designed. For full thread-locking guidance and lubrication options, see our Thread Locking & Sealing Guide. Nyloc Alternatives — When a Different Lock Nut Is the Right Choice Nyloc is not the answer for every vibration-prone joint. Three main alternatives exist in AU supply, each with a defined sweet spot. All-metal lock nuts — DIN 980 V Stover The DIN 980 V (Stover-pattern) all-metal lock nut achieves vibration resistance through metal-on-metal interference rather than a polymer insert. The top section of the nut is slightly distorted from circular — the threads are pressed into a tri-lobular or out-of-round shape. As the bolt winds in, the metal threads of the nut deform elastically against the bolt thread, creating prevailing torque without any nylon involvement. All-metal Stover nuts work at temperatures far above the nylon limit — typically rated to 200°C continuous service, with spike capability to 300°C. They are the correct fastener for: Exhaust system flanges and turbo bracket fastenings Industrial process equipment (kilns, ovens, drying lines, polymer machinery) Steam piping above 100°C service Engine-near applications and drivetrain components Welding fixtures and foundry equipment The trade-offs: higher installation torque (more force required to wind down), higher cost than equivalent Nyloc, and slightly less consistent locking force across multiple installations. They are also tolerant of more reuses than Nyloc — typically rated for 5–10 cycles before locking degrades meaningfully. Serrated flange nuts — DIN 6923 (whiz nuts) A serrated flange nut combines a hex nut, a flat washer-equivalent flange, and a series of radial serrations on the underside of the flange. The serrations bite into the bearing surface as the nut tightens, creating a locking effect from the joint surface rather than from the nut threads. Standard pairing: a high-speed assembly fastener where parts count and assembly time matter more than reusability. Whiz nuts are most commonly seen in automotive bracket assembly, sheet metal fastening, and high-volume production where the integrated washer + locking effect saves an assembly step. They mark the bearing surface (the serrations dig into the workpiece), so they are not appropriate for finished or coated surfaces. Threadlocker — Loctite 243 / 263 / 277 A chemical alternative — apply Loctite (or equivalent threadlocker) to the bolt thread before installation. The threadlocker cures in the absence of air and active metal contact, bonding the thread surfaces and resisting vibration loosening. Loctite is reusable in the sense that you can break the bond, clean the thread, and reapply — but each application is single-use. Threadlocker is the right answer when: The fastener cannot accept a Nyloc geometry (set screws, blind threads, threaded holes) Maximum strength is required and an all-metal lock nut is not feasible The joint needs to seal against fluid as well as resist vibration For the full threadlocker reference covering Loctite grades, application, and removal, see our Thread Locking & Sealing Guide. Vibration resistance hierarchy For comparing the options against application demand: Vibration severity Recommended solution Low — light machinery, light vehicles Nyloc (DIN 985) Moderate — equipment with running motors, drum kits, light engine accessories Nyloc + spring washer, or Nyloc + flat washer + threadlocker High — heavy machinery, vibration-critical assemblies, engine drivetrain All-metal Stover (DIN 980 V) or Nord-Lock washers Critical — aviation, lifting equipment, life-safety All-metal Stover plus threadlocker; engineered solution per spec Above 120°C service temperature All-metal Stover (DIN 980 V) — Nyloc not viable When to Use a Nyloc Nut The right applications for a Nyloc nut share a common pattern: vibration is a real concern, but the joint stays below 100°C in service, the assembly will not need to be disassembled and reassembled many times, and a moderate locking effect (not maximum) is sufficient. Vibration-prone assembly under 100°C — light machinery covers, equipment guards on running motors, panel fastening on vibrating equipment Outdoor and marine fittings (within material rating) — gates, fences, pool fittings, light marine fittings using stainless 304 or 316 Vehicle bodywork and interior — non-engine-bay fastenings where vibration matters Trailer hardware — light fittings, bracket attachments, toolbox mounting Furniture and equipment fitting where the design needs vibration resistance and cost is a factor General industrial assembly — anywhere the joint design assumed prevailing torque locking When NOT to Use a Nyloc Nut Equally important — the situations where a Nyloc will fail or perform below expectation. Above 120°C service temperature. Nylon softens; locking lost. Switch to all-metal Stover. Exhaust systems, manifolds, near hot machinery. Nyloc temperature ceiling makes this category off-limits. Critical aviation and lifting applications. Use engineered all-metal lock nuts to spec; never substitute Nyloc. After multiple reuses on the same nut. The nylon insert degrades each cycle; locking effect approaches zero by install three or four. Replace. Threads contaminated with grit, rust, paint, or debris. Nylon insert is destroyed before the lock effect even develops. Where the bolt does not fully pass through the nylon insert. If the bolt is too short to reach beyond the metal threads of the nut, the nylon never engages — no locking effect. Where the design specifies an all-metal or engineered lock nut. Substitution downgrades the joint. Where the assembly will see chemical attack on nylon. Strong acids, some solvents, and high-concentration ammonia degrade polyamide. Specify stainless body with verified chemical compatibility, or switch to all-metal. AIMS Industrial Nyloc Range and AU Stock The AIMS Nyloc range covers metric and imperial sizes, indoor through marine environments. Browse the full collection at the AIMS Nyloc nut collection or the broader hex lock nuts collection for all-metal alternatives alongside Nyloc options. Metric range — Bremick, Hobson Class 8 zinc-plated DIN 985 — M3 through M30 Class 10 zinc-plated DIN 985 — heavy-duty matched to Grade 10.9 bolts 304 (A2-70) stainless DIN 985 — M3 through M20 316 (A4-70) stainless DIN 985 — M4 through M16, marine and food-processing Imperial range UNC zinc-plated — 1/4" through 5/8" common stock; 9/16" available UNF zinc-plated — 1/4" through 5/8" common stock; 7/16" and 9/16" available UNF zinc-plated thin Nyloc to ASME B18.16 — for legacy and imported equipment All-metal alternatives stocked alongside DIN 980 V Stover-pattern all-metal lock nuts — for high-temperature applications above the Nyloc 120°C limit DIN 6923 / 6927 serrated flange lock nuts — for high-volume sheet-metal and bracket assembly Companion product groups Types of Nuts Guide (Art 65) — full nut family reference covering hex, Nyloc, flange, dome, castle, square, wing Wing Nut Guide (Art 132) — companion deep-dive (the hand-tightened alternative; not vibration-resistant) Socket Head Cap Screw Guide (Art 125) — pairing high-strength bolts with Nyloc Button Head Socket Screw Guide (Art 174) — pairing context Types of Washers Guide (Art 74) — flat and spring washer pairing Thread Locking & Sealing Guide (Art 44) — Loctite alternative to Nyloc Bolt Grade Chart (Art 11) — matching nut grade to bolt grade Frequently Asked Questions What is a Nyloc nut? A Nyloc nut is a hex nut with a nylon (polyamide) ring fitted into the top of the body, designed to grip the threads of a bolt or threaded rod and prevent the joint from loosening under vibration. The nylon insert deforms elastically as the bolt thread passes through, creating prevailing torque (friction independent of clamping load). "Nyloc" is the original brand name (Nyloc Corporation) and is now used generically across the Australian fastener industry. Also called Nylock nut, nylon insert lock nut, stop nut, or elastic stop nut. What is a Nyloc nut used for? Nyloc nuts are used wherever a threaded joint needs to resist vibration loosening at temperatures below 120°C. Common applications include light machinery covers, equipment guards on running motors, vehicle bodywork (non-engine-bay), trailer hardware, marine fittings (using stainless 316), pool fittings, gate hardware, furniture, light industrial assembly, and any joint where the design specifies prevailing torque locking. They are not appropriate for high-temperature applications (exhaust, manifolds, kilns) or critical aviation and lifting equipment, where all-metal lock nuts (DIN 980) are required. What's the difference between a Nyloc nut and a regular hex nut? A regular hex nut relies entirely on thread friction and joint clamping load to stay tight. Under vibration, that friction can cycle and the nut backs off slightly with each pulse, eventually loosening completely. A Nyloc nut adds a nylon insert at the top of the body that grips the bolt thread independently of clamping load — creating prevailing torque (friction that resists rotation regardless of joint load). The Nyloc stays tight under vibration where a regular hex nut will loosen. What's the difference between DIN 985 and DIN 982 Nyloc nuts? Both are metric Nyloc nut standards with identical locking mechanisms — the difference is the overall height. DIN 985 (also called ISO 10511) is the low-profile / thin variant — the AU industrial default. DIN 982 (ISO 7040) is the standard / regular-height variant with a taller body and slightly more thread engagement. DIN 985 is what AU buyers receive when ordering "M-something Nyloc" without specifying. DIN 982 is preferred in heavy-duty or high-vibration applications where longer thread engagement matters; it is less commonly stocked in AU general supply. What temperature can a Nyloc nut withstand? Standard nylon (polyamide 6 or 6/6) used in Nyloc inserts retains elasticity between approximately −40°C and +120°C in service. Above 120°C the nylon softens, the prevailing torque grip on the bolt thread reduces, and at sustained service above 130–140°C the insert deforms permanently. Above this point, the Nyloc becomes mechanically a regular hex nut with a useless plastic ring — the locking effect is lost. For applications above 100°C in service, switch to an all-metal lock nut (DIN 980 V Stover-pattern), which is rated to roughly 200°C continuous service. Can Nyloc nuts be reused? Manufacturer guidance is single-use — Bremick, Hobson and the major fastener brands universally recommend replacing Nyloc nuts after one install/remove cycle. The first time the bolt thread cuts through the nylon, it creates a thread profile in the polymer; each subsequent cycle reduces locking effectiveness further. Field practice varies by application criticality — workshop and hobby assembly often reuses Nyloc nuts without issue, but vehicle suspension, lifting equipment, structural and aviation applications should always replace. Practical inspection: if the nut spins freely down the bolt without nylon resistance, the lock effect is gone — replace. How does a Nyloc nut work? The nylon insert at the top of the nut sits in an unthreaded section of the body. When a bolt is wound through the nut, the bolt thread engages the metal threads first as normal, and then enters the nylon insert. The nylon is slightly under-sized relative to the bolt thread, so it deforms elastically as the thread passes through. The deformed nylon grips the bolt thread, creating prevailing torque (friction that resists rotation independently of clamping load). This is why Nyloc nuts stay tight under vibration even when the joint clamping force is reduced or temporarily lost. What's the Australian standard for Nyloc nuts? There is no AS/NZS-specific Nyloc nut standard. Australian industrial supply universally references the international standards: DIN 985 / ISO 10511 for the low-profile (thin) metric variant, and DIN 982 / ISO 7040 for the standard-height metric variant. ASME B18.16 covers the imperial UNC/UNF Nyloc nuts seen on imported American equipment. Property class designation follows the same numbering as standard hex nuts (Class 8, Class 10) for carbon steel and A2-70 / A4-70 for stainless. What's the difference between a Nyloc nut and an all-metal lock nut? A Nyloc nut achieves vibration resistance through a nylon insert that grips the bolt thread by elastic deformation. An all-metal lock nut (typically DIN 980 V Stover-pattern) achieves the same effect through metal-on-metal interference — the top section of the nut is slightly distorted from circular, so the metal threads themselves deform elastically against the bolt thread. Key differences: all-metal nuts work at much higher temperatures (rated to 200°C continuous service vs Nyloc's 120°C limit), tolerate more reuses (5–10 cycles vs single-use), require higher installation torque, and cost more. Choose all-metal for high-temperature, heavy-vibration, or critical applications; choose Nyloc for general industrial work below 120°C where cost matters. What size Nyloc nut do I need for an M8 bolt? An M8 bolt takes an M8 Nyloc nut. The metric thread sizing is identical between bolt and nut. An M8 Nyloc to DIN 985 has a 13 mm across-flats (AF) hex measurement — the same as a standard M8 hex nut, so a 13 mm spanner fits both. Approximate body height is 9.5 mm. Match the property class to the bolt grade — Class 8 nut for Grade 8.8 bolt, Class 10 nut for Grade 10.9 bolt. Are Nyloc nuts available in stainless steel? Yes — both 304 (A2-70) and 316 (A4-70) stainless are widely stocked. Choose 304 for general indoor and most outdoor applications away from salt water; choose 316 for marine, coastal industrial sites within roughly 1 km of the surf, swimming pool fittings, food processing brines, and chemical environments. AIMS holds metric M3 through M16 in 316 stainless and a wider range in 304. Apply anti-seize to the bolt thread before installation to prevent stainless thread galling — the nylon portion of the Nyloc does not need lubrication. Can a Nyloc nut be used outdoors? Yes — provided the material is matched to the environment. Zinc-plated carbon steel Nyloc is suitable for sheltered outdoor and most light outdoor use; for full weather exposure choose 304 stainless; for marine, coastal industrial within 1 km of surf, swimming pool fittings or chemical environments, choose 316 stainless. The nylon insert itself is unaffected by normal outdoor exposure — UV degradation of the insert is minor over typical service life. Ensure the threads are clean before installation; outdoor applications often expose threads to grit and rust that destroys the nylon insert before locking can develop. What are the other names for a Nyloc nut? Several names refer to the same fastener: Nyloc nut (dominant Australian trade term, after Nyloc Corporation), Nylock nut (common spelling variant), nylon insert lock nut (engineering term), nylon insert nut, stop nut and elastic stop nut (older trade language, mostly American), ESL nut (engineering abbreviation), and self-locking nut (generic engineering term that also covers all-metal alternatives). On AU industrial drawings and parts lists, "Nyloc" or "DIN 985" are the most common designations. How tight should a Nyloc nut be tightened? Tighten a Nyloc nut to the same torque as a standard hex nut of the same size and grade — the nylon insert does not change the recommended tightening torque. The locking effect is independent of clamping load. Note that installing a Nyloc requires more torque than a standard nut to wind it down (because the nylon grip resists rotation from the moment the bolt thread engages the insert) — this is correct and intended, the prevailing torque mechanism doing its job. The final clamping torque is what matches the standard nut spec; the additional run-down torque is the locking effect engaging. When should I NOT use a Nyloc nut? Avoid Nyloc nuts in applications above 120°C service temperature (exhaust systems, manifolds, kilns, ovens, near hot machinery), in critical aviation and lifting equipment where engineered all-metal lock nuts are required by spec, where the bolt is too short to fully pass through the nylon insert (the lock effect needs the bolt thread to enter the insert), where threads are contaminated with grit / rust / paint / debris (the nylon insert is destroyed before locking develops), where the assembly will see chemical attack on nylon (strong acids, some solvents, high-concentration ammonia), and after multiple reuses where the nylon has degraded. For above-120°C service, switch to all-metal Stover (DIN 980 V); for chemical exposure, switch to stainless body with verified compatibility or all-metal lock nut. Need the right spanner for that bolt? Our Spanner Size Chart lists every common metric and imperial size. Pair this with our Metric Bolt Size Guide for the thread pitch, AF dimension and grade options at every common size. People Also Ask — Nyloc Nuts Q: What is a nyloc nut used for? A nyloc nut (nylon insert lock nut) is used wherever vibration or movement could cause a standard nut to loosen over time. The nylon insert grips the bolt thread, resisting self-loosening without thread adhesive. Common applications include automotive, machinery, conveyor systems, and any assembly subject to cyclic loading or vibration. Q: How many times can a nyloc nut be reused? Nyloc nuts are designed for single use. Each removal cycle deforms the nylon insert slightly, reducing its locking grip. For safety-critical or high-vibration assemblies, always fit a new nyloc nut. In low-load, non-critical applications careful reuse is sometimes accepted, but replacing with a new nut is the recommended practice. Q: What is the difference between a nyloc nut and a standard hex nut? A standard hex nut relies on friction between thread surfaces alone and can loosen under vibration. A nyloc nut adds a nylon insert at the top that deforms around the bolt thread, providing positive locking resistance. Nyloc nuts require greater installation torque and maintain their clamping force much better under dynamic or vibrating loads. Q: Can nyloc nuts be used at high temperatures? No — the nylon insert softens above approximately 80–90°C, significantly reducing its locking effectiveness. For elevated-temperature applications such as engine bays, exhaust components, or industrial ovens, use all-metal prevailing-torque lock nuts (serrated flange or distorted thread types) instead of nyloc nuts. Q: What grades and materials are nyloc nuts available in? Nyloc nuts are available in Class 5 through Class 10 property classes in carbon steel, and in stainless steel grades 304 and 316 for corrosion-resistant applications. Marine, food processing, and outdoor environments typically use stainless 316. Match the nut grade to the bolt grade — never mix grades in a structural joint. For bin and hopper flow-aid hardware, browse the AIMS industrial pneumatic vibrator range (ball, piston, and turbine). For die nuts, see our die nuts range stocked across Australia.A nyloc nut and a threadlocker solve the same problem — vibration loosening — by different means: one mechanically, one chemically. They can be used together on critical joints, or a threadlocker on a plain hex nut can do the job on its own where a nyloc isn't practical. See our Loctite Threadlocker Guide for grade selection.
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