Product Guides
How to Identify High Tensile Bolts for Your Projects
Quick & Easy: How to Identify High Tensile Bolts When your project demands extra strength – whether it's for a vehicle upgrade or heavy machinery – high tensile bolts are a must. At AIMS Industrial, we’re here to help you understand what to look for in a fun and easy way. Understanding Bolt Grades Bolt grades indicate the strength and durability of the bolt. In Australia, you will commonly encounter these grades: Grade Description 8.8 Medium carbon steel, quenched and tempered 10.9 Alloy steel, quenched and tempered for extra strength 12.9 Alloy steel with the highest tensile strength How to Identify High Tensile Bolts Look for the grade markings stamped on the bolt head – these numbers tell you the bolt’s strength: 8.8: Marked with "8.8" 10.9: Marked with "10.9" 12.9: Marked with "12.9" Choose the Right Bolt for Your Application Not every project requires the same level of strength. Here are some of our top picks available at AIMS Industrial: Metric Hex Bolt - Grade 8.8 High Tensile Zinc Finish – Ideal for many structural applications. Bumax 10.9 Stainless Steel High Tensile Hex Bolt – Perfect for projects needing extra corrosion resistance. M20 x 24 x 80 Socket Head Shoulder Screw Plain High Tensile G12.9 – The top choice when maximum strength is essential. Safety, Time and Money Selecting the right high tensile bolt is crucial for the safety and longevity of your projects. Always check the bolt head for grade markings and choose the one that best fits your application. Explore our full range of high-quality fasteners on our Bolts Collection for more options. For a comprehensive guide CLICK HERE At AIMS Industrial, we make sure you have the right tools for every project. Happy bolting! People Also Ask — High-Tensile Bolt Identification Q: How can I tell if a bolt is high-tensile? The quickest way is to read the head markings. Metric high-tensile bolts carry a property class number stamped on the head, such as 8.8, 10.9 or 12.9 — the higher the number, the stronger the bolt. Imperial bolts use radial lines on the head, where more lines indicate a higher grade. A bolt with no markings is generally a low-grade commercial fastener and should not be assumed to be high-tensile. So before relying on a bolt for a structural or high-load joint, check the head: a clear property class number or a set of radial lines tells you it is a graded, high-tensile fastener rather than a general-purpose one. Q: What do the numbers like 8.8, 10.9 and 12.9 mean? These are metric property class markings, and they encode the bolt's strength. The first number relates to the bolt's tensile strength and the second to its yield strength as a proportion of tensile, so a higher pair of numbers means a stronger, harder bolt. In practice, 8.8 is the common high-tensile grade for general engineering, 10.9 is used for more demanding joints, and 12.9 is among the highest standard grades for the most heavily loaded applications. The system lets you compare bolts at a glance — a 10.9 is stronger than an 8.8 — which is why matching the property class to the joint's requirement matters. Q: How do imperial bolt grade markings work? Imperial bolts show their grade through radial lines stamped on the head rather than numbers. No lines indicate a low-grade bolt, three radial lines indicate a common medium-high grade, and six radial lines indicate a higher grade again — more lines means a stronger bolt. Because the markings differ from the metric number system, it is important not to confuse the two: an unmarked head is not the same as a graded metric bolt. When working in imperial, count the radial lines to read the grade, and confirm against the supplier's specification if the joint is critical. Mixing up imperial and metric grade systems is a common and avoidable error. Q: Why does using the correct bolt grade matter? Bolt grade determines how much tension and shear a fastener can safely carry. Using a bolt that is too low a grade in a high-load joint risks the bolt yielding or failing, which in structural, lifting or machinery applications can be dangerous. Conversely, the grade affects the correct tightening torque, so fitting the wrong grade and torquing it as if it were another can over- or under-stress the joint. Matching the bolt's property class or grade to the engineering requirement — and torquing it accordingly — is what keeps the joint safe and reliable. When a joint is critical, always confirm the specified grade rather than substituting whatever is on hand. Q: Can I substitute a higher-grade bolt for a lower one? It is often acceptable to use a higher-grade bolt where a lower grade is specified, since the stronger bolt has greater load capacity — but it is not automatic. Higher-grade bolts are harder and can be more brittle, the correct tightening torque changes with grade, and some applications deliberately specify a particular grade for reasons such as controlled failure or ductility. Going the other way — substituting a lower grade where a higher one is called for — should never be done, as it under-rates the joint. The safe rule is to match the specified grade where you can, and only step up after confirming the higher grade and its torque suit the application. For champion, see our champion range stocked across Australia. Need bumax? Browse the AIMS range at bumax.
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U-Bolt Guide: Bend Types, Pipe Clamp, Exhaust, Leaf Spring & Roof Rack Applications
U-bolts decoded: square vs semi-round vs round bend, leaf spring replacement safety, exhaust clamp crush mechanism, pipe mounting and the U-bolt vs Bull Dog grip distinction.
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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 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. Share: Share on Facebook Share on X Pin on Pinterest Previous Post Bolt Extractor Guide: Easy-Outs, Spiral Flute, Multi-Spline & Bolt Extractor Sockets Next Post Reciprocating Saw Blade Guide: TPI Selection, Bi-Metal vs Carbide, Wood/Metal/Demolition Blade Choice People Also Ask — Grease Nipples & Zerk Fittings Q: What is a grease nipple and what is it used for? A grease nipple (also known as a Zerk fitting, grease fitting or lubrication nipple) is a small threaded fitting installed in machinery to allow grease to be injected into a bearing, joint or pivot point through a grease gun. The fitting contains a spring-loaded ball check valve that opens under pressure from the grease gun and closes when pressure is removed, preventing contaminants from entering. They are found on wheel hubs, suspension joints, universal joints, conveyor bearings, agricultural equipment and almost any machine with a grease-lubricated bearing. Q: What is the difference between straight, 45-degree and 90-degree grease nipples? Straight grease nipples suit locations where the grease gun can be applied in a straight line, typically on the side of a bearing housing or joint. 45-degree and 90-degree angled nipples are used where space restrictions prevent straight-on access — the angled body points the inlet in a more accessible direction while the grease flow is redirected. Using the wrong angle can make greasing awkward or impossible in confined machinery. Where access is very restricted, hydraulic-style flush nipples (button-head) are also available. Q: How do I know when a bearing needs re-greasing? Re-greasing intervals depend on bearing speed, temperature, load and operating environment. Manufacturer-specified intervals are the primary guide. In the absence of specifications, a practical rule is to re-grease at a set number of operating hours based on the bearing size and speed. Signs that a bearing needs grease include elevated operating temperature, increased noise, or visible grease depletion. Avoid over-greasing — excessive grease builds up pressure inside the bearing, generates heat and can force seals. Re-grease slowly and stop as soon as clean grease appears at the seal lips or purge point. Q: Why is my grease gun not pumping grease through the nipple? The most common causes are a blocked or frozen grease nipple ball valve, a damaged coupling that is not sealing over the nipple head, or hardened or contaminated grease in the nipple passage. Try removing the nipple and cleaning the ball valve, or replace the nipple. Check that the grease gun coupler is fully seated and not leaking around the nipple. In cold conditions, grease becomes much harder to pump — warming the grease gun or the fitting can help. If the bearing housing is already overfull, grease will not pump in because there is no room for it to go. Q: What thread size are most standard grease nipples? The most common thread sizes for grease nipples in metric markets are M6 × 1.0 (common on European and Australian equipment) and M8 × 1.0. In imperial applications, 1/4-28 UNF and 1/8-27 NPT are the most common. Before replacing a grease nipple, identify the thread by using a thread gauge or measuring carefully — cross-threading a replacement nipple in an aluminium or cast iron housing can cause expensive damage. Grease nipples are available in a wide range of metric and imperial thread sizes to suit different equipment. Related Posts bordo Reciprocating Saw Blade Guide: TPI Selection, Bi-Metal vs Carbide, Wood/Metal/Demolition Blade Choice May 11, 2026 AIMS Industrial bolt-extractor Bolt Extractor Guide: Easy-Outs, Spiral Flute, Multi-Spline & Bolt Extractor Sockets May 11, 2026 AIMS Industrial Charts Choosing the Right Drill Bit: Types, Sizes & Charts May 11, 2026 admin
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Bolt extractors: spiral fluted, square, multi-spline and bolt extractor sockets compared. Left-hand drills, hardened-bolt failure mode and weld-a-nut technique.
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How to Identify High-Tensile Bolts: Grade Markings Decoded
Read bolt head markings, decode ISO 898-1 metric property classes (4.6, 8.8, 10.9, 12.9) and SAE J429 imperial grades, check AS/NZS 1252.1 structural bolts, and avoid counterfeits. Practical Australian guide with selection tables.
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Fastener Quick Guide: Thread, Grade, Head & Drive Types
If you spend any time in a workshop, on site, or specifying parts at a desk, fasteners are one of those things you stop noticing — until the wrong one fails. This guide walks through every major fastener category in plain language, lines up the Australian Standards that apply, and points you to deep guides where you need them. Use it to orient yourself, decode a part number, or confirm you're holding the right thing before you torque it down. Fastener Categories at a Glance Every fastener falls into one of a handful of families. Here's the rapid-look table — what it does, where you see it, and the headline Australian Standard. Category Common AU Use Headline Standard Hex bolts & set screws Steel structures, plant, machine assembly AS 1110 / AS 1111 (metric ISO precision & product grade hex) Socket head cap screws Tooling, jigs, hydraulic blocks, machine guards ISO 4762 / DIN 912 Nuts (hex, nyloc, castle, flange) Mating threads on bolts and studs AS 1112 series Washers (flat, spring, Belleville) Load spreading and anti-loosening AS 1237 (flat), AS 1252 (HSFG assemblies) Screws (self-tapping, wood, machine) Sheet metal, timber, fixtures AS 3566 (self-drilling Class 3/4 coatings) Anchors (chemical, mechanical, dynabolt) Concrete, masonry, brick ETA / ICC-ES + AS 5216 (post-installed in concrete) Rivets, pins, threaded rod Sheet joining, alignment, structural ties AS 1444 (steel), AS 2465 (precision) Stainless steel fasteners Marine, food & pharma, outdoor exposure AS 4291 (mech properties) — A2 / A4 grades If you already know which family you're in, jump down. If you're staring at a fastener and not sure, the next section covers thread systems — almost every mis-buy starts there. Thread Systems — Metric, Imperial & British Thread system is the single most common source of fastener mistakes in Australia. We use metric on most modern equipment, but legacy plant, US machinery, and the plumbing/gas trades keep imperial and British threads alive. The four families you'll meet: Metric (ISO 261 / ISO 262) Standard on every new piece of locally specified equipment. Designated as M(diameter) × (pitch) — for example M10 × 1.5. If the pitch is omitted, assume the coarse default for that diameter. Fine pitches (M10 × 1.25, M12 × 1.25) exist for vibration-prone joints or thin-wall applications. Use a thread pitch gauge or a known-good companion fastener to confirm before ordering. Unified Thread Standard (UTS) — UNC, UNF, UNEF The US imperial system. Diameter is in inches or as a number gauge (#6, #8, #10), and pitch is expressed as threads per inch (TPI). UNC (coarse) is the default for general work; UNF (fine) shows up in automotive and aerospace; UNEF (extra fine) is niche. A 1/4-20 UNC bolt is 1/4" diameter, 20 TPI. UTS turns up on US-built machinery, older Holden/Ford gear, and a lot of imported tooling. British threads — BSW, BSF, BSP / BSPP / BSPT, NPT BSW (Whitworth) and BSF (Fine) are largely retired from new builds but still found on older Australian equipment, classic cars, and heritage steel. BSP is the dominant pipe thread for fluid & gas work in Australia (parallel BSPP for sealing-by-O-ring, tapered BSPT for thread-seal). NPT is the US tapered pipe thread — common on imported pneumatics and US fluid power gear. BSP and NPT look similar but are NOT interchangeable; mixing them strips threads and leaks. Full BSP vs NPT vs UNC guide. Quick metric-to-imperial size cross-reference For body diameter only — never a thread-matching reference. Use this when you're trying to pick a spanner or visualise sizes, not when you're sizing a replacement bolt. Metric (mm) Closest imperial body Closest UTS thread M3 1/8" #5-40 / #6-32 M4 5/32" #8-32 M5 3/16" #10-24 M6 1/4" 1/4-20 UNC M8 5/16" 5/16-18 UNC M10 3/8" 3/8-16 UNC M12 1/2" 1/2-13 UNC M14 9/16" 9/16-12 UNC M16 5/8" 5/8-11 UNC M20 3/4" 3/4-10 UNC M24 1" 1"-8 UNC For the deep cross-reference with full pitch data, tap drill sizes, and tightening info, see our Metric & Imperial Fastener Reference Guide and the Tap Drill Size Chart. Property Classes & Grades Property class tells you how strong the steel is — the most important factor after thread match. Mismatch a grade and you either over-engineer (waste money) or under-engineer (risk failure). Three systems are in active use in Australia. Metric property class (ISO 898-1) Marked on the head as a two-number code — for example 8.8, 10.9, 12.9. The first digit, multiplied by 100, gives the nominal tensile strength in MPa. The second digit, divided by 10, gives the yield-to-tensile ratio. 4.6 / 5.6 / 6.8 — low/medium strength. General-purpose mild steel bolts. OK for non-critical work. 8.8 — the workhorse of structural and mechanical work. ~800 MPa tensile, ~640 MPa yield. Galv or zinc plated. Specify for any load-bearing joint unless engineer says otherwise. 10.9 — high tensile. Used in structural HSFG assemblies (AS/NZS 1252), heavy machinery, automotive. Almost always plain or black, occasionally zinc. 12.9 — very high tensile. Socket head cap screws, hydraulic blocks, precision tooling. Brittle if mis-applied — not a "stronger 10.9", use only where specified. If you're identifying high-tensile in the field, see How to Identify High Tensile Bolts. For torque values per grade and size, the Metric Bolt Torque Chart is the reference. Full background → Bolt Grade Chart. Imperial — SAE J429 The US grade system uses radial slashes on the head: Grade 2 — no head markings. Low-carbon steel. Common in hardware-store bolts. Grade 5 — three radial slashes. Medium-carbon, heat-treated. Loosely equivalent to metric 8.8. Grade 8 — six radial slashes. Alloy steel, quenched & tempered. Loosely equivalent to metric 10.9. SAE grades are common on imported US automotive, mining gear, and pre-2000 plant. Don't substitute SAE for metric on a thread basis — even at near-equivalent strength, the pitches don't match. Stainless steel — ISO 3506 / AS 4291 Stainless grades are marked as a material code + property class, separated by a hyphen — for example A2-70 or A4-80. A2 — austenitic stainless, broadly equivalent to 304/18-8. General outdoor, marine-adjacent, food service. A4 — austenitic stainless with molybdenum (316). Required for marine, coastal, chloride, food & pharma. -70 — 700 MPa tensile, standard cold-worked. The volume product. -80 — 800 MPa tensile, higher cold-work. Stronger but harder to install, more galling risk. Full guide → Stainless Steel Fastener Grades Explained. For coastal builds, marine, food & pharma, default to A4-70 (316) and use anti-galling lubricant on assembly. Head Types Head choice affects clamp force, tool access, appearance, and removal risk. The big ones in Australian workshops: Hex head The default for structural and mechanical bolts. Standard hex (AS 1110/AS 1111) accepts a spanner or socket. Easy to torque to spec, easy to remove. Specify hex unless you have a reason not to. Socket head cap screw (SHCS) Cylindrical head with internal hex drive. Sits flush in a counterbore, tolerates higher torque than equivalent hex (denser head material), and is the go-to for machined assemblies, hydraulic manifolds, jigs and fixtures. Almost always Grade 12.9. Full background → Socket Head Cap Screw Guide. Button head Low-profile dome with internal hex. Decorative, fingertip-safe, but lower clamp force than SHCS (thinner head, less material under the recess). Use where appearance matters or knuckle clearance is tight. Not for high-torque structural work. Countersunk (CSK) — flat & raised Tapered head designed to sit flush in a chamfered hole. Standard angles in Australia are 90° (metric ISO) and 82° (UTS imperial — common on US sheet-metal hardware). Mixing the two leaves the head proud or distorts the chamfer. Available with Phillips, slotted, Torx, or socket drives. Pan, dome & truss Pan head: low cylindrical sides with rounded top — the default machine-screw head. Dome (round head): higher-profile, more decorative. Truss: wide flange-style head spreading load on soft materials (sheet metal, plastics). Used widely across covers, panels, signage. Flange head Integrated serrated or smooth washer under the head — spreads load and resists loosening without needing a separate washer. Common on automotive, mining haul-truck, and white-goods chassis work. Once torqued, the serrations bite the substrate. Carriage / coach bolt head Smooth dome with a square shoulder under the head. Square shoulder bites into timber and prevents rotation while the nut is tightened from below. Old-school but unbeatable for timber framing, deck framing, gates and fencing. Full background → Coach Bolt & Coach Screw Guide. Cup & tee head Cup head (round head with square shank, similar to carriage) used on agricultural and trailer gear. Tee head — wide T-shape — for slot mounts and machine T-slots. Full deep-dive across all head families → Screw Head Types Guide. Drive Types Drive type is how you turn the fastener. Wrong drive = stripped head and a stuck bolt. The major drives: Hex / Allen (internal hex) Hexagonal recess in the head, turned with an Allen key or hex bit. The default drive for socket head cap screws, button head, low-head SHCS and many grub screws. Sizing is the across-flats measurement (e.g. 5 mm hex on an M8 SHCS). Imperial Allen drives still appear on US tooling. Torx (star, 6-lobe) Six-lobed star recess. Higher torque transfer than hex, less cam-out than Phillips, and the security versions (Torx Plus, Torx Security with pin) are vandalism-resistant. Used widely on cars, white goods, electrical assembly. Sizes are T(number) — e.g. T25, T30. Full guide → Torx Bit Sizes Guide. Phillips Cross-shaped recess (PH0-PH4). Designed in the 1930s to cam out under high torque (preventing over-tightening on assembly lines). That cam-out is the trade-off — Phillips strips easier than any other modern drive. Use where the spec requires Phillips; otherwise prefer Pozidriv, Torx, or hex. Pozidriv (PZ) Looks like Phillips with extra fine ribs at 45° in the recess. Engages deeper, cam-outs less, transmits more torque. Common on European screws and modern self-tapping fasteners. Use a Pozidriv bit (not Phillips) — the wrong bit destroys the head. Slotted (flat) The original screw drive. Centring is poor, cam-out is high, and it's only specified where heritage appearance matters or where field-improvised drivers (coin, knife edge) are useful. Avoid for production work. Square (Robertson) Square recess. Excellent torque transfer, self-centring, common in cabinet-making and construction screws. Underused in industrial work but loved by joiners and timber-frame installers. Combination drives Phillips/slot, Phillips/square, Torx/hex — pick the bit that fits best. Avoid double-driving (don't alternate Phillips and slot on the same screw; you'll round both). Nut Types Nuts are not a commodity. The choice between hex, nyloc, castle, flange and dome decides whether the joint loosens, comes apart, or seizes. The main families: Standard hex nuts The default. AS 1112.1 series for ISO metric hex nuts. Match the grade to the bolt — Grade 8 nut on Grade 8.8 bolt; Grade 10 nut on 10.9; Grade 12 nut on 12.9. A weak nut on a strong bolt strips the nut threads before reaching torque spec. Nylon insert lock nuts (Nyloc) Hex nut with a nylon collar pressed into the top. The collar grips the bolt thread and resists vibration loosening. Use once where possible — the nylon loses grip on each reuse, and is rated to about 100-120 °C continuous (the nylon softens above that). Detailed background → Nyloc Nut Guide. AIMS carries a strong Nylon Lock Nuts range. All-metal lock nuts (prevailing torque) The nut thread itself is deformed or has a metal ring that grips the bolt. Higher temperature rating than Nyloc, can be reused more times, and trusted in vibration-heavy automotive and rail work. Castle nuts Crown-shaped slots cut into the top of a hex nut. A cotter pin (split pin) drops through a transverse hole in the bolt and through one slot, mechanically locking the nut against rotation. The default for tapered-joint applications — tie-rod ends, ball joints, axle nuts. Critical safety rule: always tighten to the next slot, never loosen back. Loosening releases the taper-seat clamping force. See stuck bolts removal guide for related rigging. Flange nuts Integrated wide flange under the hex. Spreads load, reduces marking on soft substrates, and the serrated variants resist loosening. Auto chassis and mining equipment. Dome / cap / acorn nuts Hex nut with a sealed dome over the bolt end. Finger-safe, weatherproof, decorative. Common on guardrail and trailer assemblies. The bolt has to be short enough to fit inside the dome. Wing nuts Two wings for hand tightening. Light-duty assemblies, clamps, fixtures requiring frequent removal. K-lock / Kep nuts Hex nut with a captive serrated free-spinning washer. Saves a step on assembly lines. Common on electrical and sheet-metal panel work. Purlin / cup nuts Roofing and cladding nuts designed for purlin connections — wide load distribution under the nut, often supplied as bolt+nut+washer assemblies. See Purlin Bolts & Nuts. For lock nuts other than nylon, AIMS carries Hex Lock Nuts and the full Nuts range. Washer Types Washers are not optional decoration. They spread load, prevent thread damage to the substrate, and (in their lock variants) help resist loosening. The families: Flat washers Round, flat steel discs. Three common Australian patterns: Standard flat (AS 1237.1) — the everyday workhorse. Inside diameter sits with light clearance over the bolt thread. Heavy / structural (AS 1252) — thicker, larger OD. For HSFG (high-strength friction grip) structural assemblies. Fender / mudguard — wide OD relative to ID. Spreads load on soft or thin substrates (sheet metal, timber, plastic). See Flat & Round Washers. Spring washers (single-coil / DIN 127) Split, slightly conical. Compressed under the bolt head and the edges bite into the nut and substrate. Their effectiveness against modern vibration is debated — many engineering specifications now favour Nyloc or wedge-locking systems instead. Still standard on general workshop work. Spring Washers range. Belleville (disc / conical) washers Dished steel discs that act as springs. Maintain clamp force as the joint relaxes, expands or compresses (thermal cycles, gaskets bedding in). Stacked in series or parallel to tune spring rate. Used widely in flanged joints, gasket-sealed assemblies, and machinery with thermal cycling. Internal & external tooth lock washers Teeth around the ID (internal) or OD (external) bite into the bolt head/nut and the substrate. Cheap, effective on softer substrates. Less reliable on hard surfaces (no bite). Common on electrical earthing — the teeth cut through paint and oxide to reach base metal. Wedge-lock washers (NordLock-style) Pairs of cam washers — radial cams between the washers, serrations on the outer faces. As the joint vibrates, the cams resist back-rotation. Trusted in mining, rail, defence. Specify when vibration is critical. Sealing & bonded washers Steel washer with a vulcanised rubber (EPDM, NBR, FKM) ring on one face. Seals the bolt hole against weather, fluid, gas. Standard on roofing screws, automotive sumps, and any fluid-tight bolt hole. Don't confuse with Dowty / bonded seal washers (those have the rubber bonded inside the steel washer for hydraulic port sealing). Specialty Fasteners Beyond the main families, a handful of specialty fasteners come up often enough to be worth knowing. Set screws & grub screws Headless screws with internal hex (or slotted) drive, threaded full-length. Used in shaft collars, pulleys, knobs and adjusters where the screw must sit flush or below the surface. Point styles — cup, flat, dog, cone, knurled — each suit different gripping jobs. AIMS carries a strong Grub Screws range. Shoulder bolts (stripper bolts) Precision-ground unthreaded shoulder section sized for a slip fit, with a smaller-diameter threaded end. Used as pivots, dowels, bearing supports, and in stamping dies. ISO 7379. Don't substitute a hex bolt and washer — the shoulder geometry is the load-bearing feature. Anchor bolts & chemical anchors For concrete and masonry. Mechanical anchors (dynabolts, sleeve anchors, wedge anchors) expand inside the hole as you tighten. Chemical anchors (epoxy or vinyl ester resin into a drilled hole) suit cracked concrete, edge-of-slab work, and the highest pullout loads. AS 5216 covers post-installed anchors in concrete. See the full Anchors range. Eye bolts & U-bolts Eye bolts: forged loop on a threaded shank — lifting points and rigging attachment. Critical safety: only use rated lifting eye bolts (forged, stamped with WLL) for overhead lifting. Hardware-grade eye bolts are NOT lifting hardware. U-bolts (U-Bolts range): two-thread U shape with mating plate. For pipe brackets, suspension fittings, and trailer leaf-spring assemblies. Threaded rod (all-thread / studding) Continuously threaded steel rod sold by the metre or length. Cut to size on site for hanging supports, threaded inserts, anchor stud assemblies. Plain mild steel, galvanised, 8.8, 10.9, and stainless A2/A4 grades. Range: All Thread Rod. Rivets & rivet nuts Permanent fastening for sheet metal where you can only access one side (blind rivets), or where lower-cost mass assembly matters (solid rivets). Rivet nuts (rivnuts) install a permanent threaded insert into thin sheet. Full Rivets range. Pins — clevis, dowel, roll, cotter Clevis pins (with head and cross-hole, secured by a split pin) form pinned joints — rigging, linkages, agricultural gear. Dowel pins (precision-ground cylinders) align mated parts in tooling and machine assembly. Roll pins (spring pins) — cylindrical pins formed from spring steel, installed into a tight bore. Cotter / split pins secure castle nuts and clevis pins. Australian Standards Quick Reference The fastener standards you're most likely to meet on a drawing, in a spec, or on a certificate of conformance. currency of edition years before quoting in a formal compliance document. Standard Covers AS 1110 / AS 1110.1 / AS 1110.2 ISO metric hexagon precision bolts & screws (Grades A & B) AS 1111 / AS 1111.1 / AS 1111.2 ISO metric hexagon product grade C bolts & screws AS 1112.1–1112.4 ISO metric hexagon nuts (style 1, style 2, thin, chamfered) AS 1252 HSFG bolts, nuts & washers for structural steel — Grade 8.8/S AS 1237 series Plain washers for metric bolts, screws & nuts AS 2465 Unified hexagon bolts, screws & nuts (UNC/UNF — imperial) AS 3566 Self-drilling screws for the building & construction industries (Class 3 / Class 4 corrosion) AS 4291.1 Mechanical properties of corrosion-resistant stainless steel fasteners (A1/A2/A3/A4) AS 5216 Design of post-installed and cast-in fastenings for use in concrete ISO 898-1 Mechanical properties of fasteners — Grade 4.6 through 12.9 ISO 3506 Mechanical properties of stainless steel fasteners — A2, A4, etc. ISO 4762 / DIN 912 Socket head cap screws (SHCS) DIN 985 Prevailing torque type hex nuts with non-metallic insert (Nyloc) Selection Quick Rules Thread match comes first Never mix metric and imperial threads. The pitches don't match, and you'll either cross-thread (visible damage) or get a few turns of false engagement before the joint fails under load. If you can't read the markings, use a thread pitch gauge — every workshop should have one. Match coarse to coarse and fine to fine within the same system. Match grade across the joint The nut grade must match or exceed the bolt grade. Mismatched grades are one of the most common preventable failures — a Grade 6 nut on a Grade 10.9 bolt will strip its threads well below the bolt's rated torque. Torque to spec, not by feel Tightening "until it feels right" overloads small fasteners and under-loads large ones. Use the Metric Bolt Torque Chart as your reference. Wet/dry/lubricated torque values are not the same — read the spec carefully. Match the corrosion environment Indoor, dry, climate-controlled: zinc or plain finish is fine. Outdoor, exposed to weather, coastal: galvanised or stainless A2 minimum. Marine, splash zone, food & pharma: stainless A4 (316) and anti-galling lube on assembly. Mixing dissimilar metals (steel bolt in aluminium plate, untreated) causes galvanic corrosion — use a barrier or matched-material fastener. Plan for re-use (or don't) Nyloc nuts: ideally single-use. Critical structural fasteners (HSFG, head studs, suspension): always replace per OEM spec. Adhesive thread locker (Loctite): clean off old residue with primer before re-applying. If a joint comes apart and the threads look polished or burred, replace the fastener. Tooling matters A good caliper measures bolt diameter and head. A thread pitch gauge confirms pitch. A torque wrench (calibrated, in date) delivers spec torque. Spending five extra minutes with the right tool prevents an hour fixing a stripped joint. AIMS' Note on Fastener Sourcing AIMS stocks the volume range across Hobson, Bremick, Bumax, Sutton, Inox World and other Australian-trusted brands — see the full Fasteners range, or jump into a specific family: Bolts, Nuts, Washers, Screws, Anchors, Rivets, All Thread Rod. For volume runs, custom sizes, certified material (mill certs, hot-dip galv to AS/NZS 4680), or anything you can't find on-site, give us a call. When you ring, having the following handy speeds the quote: thread system + diameter + pitch + length, grade or material, head type, finish/coating, quantity required, and the application. If it's a replacement, the part number off the old fastener (or a clear photo of the head markings) is often enough. For broader Australian-made and stocked-in-AU brands: Hobson (full range), Bremick, Bumax (high-tensile stainless), Inox World, Sutton Tools (cutting/threading consumables). Frequently Asked Questions What's the difference between a bolt and a screw? In Australian practice, a bolt is designed to pass through a clearance hole and be secured by a nut on the far side. A screw threads directly into a mating threaded hole (tapped material or female thread). Many fasteners blur the line — socket head cap screws are technically screws by this rule even when used like bolts. Use the manufacturer's terminology if certifying to a spec. How do I tell metric from imperial without a thread gauge? Look at the head markings. Metric uses property class digits like 8.8 or 10.9. Imperial SAE uses radial slashes (Grade 5 = three slashes, Grade 8 = six). If the diameter is a clean millimetre value (M6, M8, M10) it's metric; if it's a fractional inch (1/4", 3/8", 1/2") or a # number (#8, #10), it's imperial. A thread pitch gauge resolves any doubt in 10 seconds and costs less than one mis-bought box of bolts. Can I use a Grade 12.9 bolt anywhere I'd use a Grade 8.8? Not safely as a blanket rule. 12.9 is harder and more brittle than 8.8 — it can fail suddenly under shock loads or in corrosive environments (hydrogen embrittlement risk is higher). 12.9 is specified by design where its strength is needed in compression-clamped joints with controlled torque. For general structural and mechanical work, 8.8 is the engineered choice — substitute up only with engineering sign-off. What's the maximum service temperature for a Nyloc nut? The nylon insert is rated for about 100-120 °C continuous service. Above that the nylon softens and loses grip, and the locking function fails. For higher-temp service use all-metal prevailing torque lock nuts, castle nuts with split pins, or wedge-lock washers. Full background → Nyloc Nut Guide. manufacturer-specific upper limits before high-temp service. When do I need stainless A4 vs A2? A4 (316 grade, with molybdenum) for marine exposure, coastal builds within ~1 km of breaking surf, chloride-rich industrial environments, food & pharma. A2 (304-equivalent) for general outdoor in low-chloride environments and indoor wet areas. If in doubt and you're within sight of the ocean, specify A4 — the upcharge is small against the cost of replacing rusted fasteners later. Why does my Phillips bit keep stripping screws? Phillips was designed to cam out — that's the original feature, not a defect. The trade-off is poor tolerance for misalignment, worn bits, and over-torque. Three fixes: (1) use a fresh bit, (2) press firmly into the screw and torque slowly, (3) where the spec allows, switch to Pozidriv, Torx, or hex drive. See the Torx Bit Sizes Guide. What thread is BSP, and is it the same as NPT? BSP (British Standard Pipe) is the dominant Australian pipe and fluid thread. It comes in BSPP (parallel — sealed by an O-ring or bonded seal washer at a port face) and BSPT (tapered — sealed by the thread itself, usually with PTFE tape or thread compound). NPT is the US tapered pipe thread. BSP and NPT have different thread angles (55° vs 60°) and different taper rates — they do not interchange. Mixing them strips threads and leaks fluid or gas. Full background → BSP vs NPT vs UNC Guide. How tight is "tight enough" for a bolt? Use a torque wrench and the Metric Bolt Torque Chart for the grade, diameter, and condition (dry, lubricated). Critical joints — structural, suspension, head studs, pressure-containing — should always be torqued to spec, not by feel. For non-critical assembly work, a calibrated torque wrench used at 70-80% of recommended dry torque is a safe default. Why does my flat washer keep loosening even with a spring washer underneath? Modern engineering research has shown that DIN 127 single-coil spring washers are not very effective against high-frequency vibration. They flatten under torque and provide minimal anti-rotation force. For real vibration resistance, use Nyloc nuts, wedge-lock washers (NordLock-style), or thread-locking adhesive (Loctite 243 medium-strength, 263 high-strength). A flat washer alone, correctly torqued, often outperforms a flat-plus-spring combination on a properly tensioned joint. What's the difference between coach screws and coach bolts? Coach bolts (also called carriage bolts) have a smooth domed head with a square shoulder under the head; the shaft is threaded only on the lower portion and is used with a nut on the far side. Coach screws (also called lag screws or lag bolts) have a hex head and a tapered wood-screw thread for direct driving into timber — no nut. Both are timber-framing fasteners. Full background → Coach Bolt & Coach Screw Guide. Are Australian fastener standards different from the rest of the world? AS standards are largely aligned with ISO and DIN equivalents — for example AS 1110 maps to ISO 4014. The Australian-specific standards mainly cover hot-dip galvanised coatings (AS/NZS 4680), structural HSFG assemblies (AS 1252), and self-drilling screws for the Australian climate (AS 3566 Class 3/Class 4). Imported fasteners marked to ISO or DIN are generally compatible with AS-specified work, but a certificate of conformance or mill certificate is the safe document when audit risk applies. How do I get a stuck or seized bolt out? The escalation ladder runs from heat + penetrant (CRC 5.56, WD-40, Loctite Freeze & Release) through impact (impact driver, breaker bar) to thread-rescue (extractor bits, left-hand drill bits) to last-resort (cut and replace). The full procedure is in the stuck bolts & nuts guide. What's the right anchor for fixing into concrete? Light load, non-cracked concrete: dynabolt or sleeve anchor. Medium load, cracked concrete possible: through-bolt or wedge anchor rated for cracked concrete. High load, edge-of-slab, or vibration: chemical anchor (epoxy or vinyl ester) with threaded rod. AS 5216 is the design standard. AIMS carries the full Anchors range — call us if you need help matching anchor to substrate. What head and drive should I use for outdoor timber decking? Stainless A2-70 (or A4-70 if coastal) self-drilling Type 17 screws to AS 3566 Class 3 (or Class 4 for severe marine) — Pozidriv or square drive, countersunk head with ribbed underhead to flush-finish into hardwood. For structural timber connections (joists, bearers, ledgers), coach screws or coach bolts (galvanised or stainless) sized per AS 1684 timber framing. What's an A2-70 marking telling me? A2 = austenitic stainless steel (broadly 304-grade equivalent, 18% chromium / 8% nickel). 70 = property class 700 MPa nominal tensile strength, cold-worked to standard hardness. For tougher applications use A2-80 (cold-worked harder, 800 MPa) — same material, higher work-hardening. For chloride / marine exposure, step up to A4-70 (316 with molybdenum). Full guide → Stainless Steel Fasteners. For pop-rivet guns and nutsert tools, browse the AIMS rivet tools collection.
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 AnnealingHeat 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
Threaded rod: all names (allthread, Booker rod, studding), grades 4.6 vs 8.8, metric sizes M6–M36, galvanised vs stainless, the nut trick for cutting, joining with coupling nuts, and acme thread explained.
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. 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. 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. 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.
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.
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