Product Guides
AIMS Tap & Die Selection Guide: Hand, Spiral Point, Spiral Flute & Forming
A practical guide to selecting the right tap and die for the thread you're cutting. Covers hand taps (taper, plug, bottoming), spiral point taps for through holes, spiral flute taps for blind holes, thread forming taps for ductile material, machine nut taps, die nuts, button dies and die holders. Includes thread system selection (metric, BSP, BSPT, NPT, UNC, UNF, BSW, BSF), tap drill sizing, brand selection across Sutton Tools and Bordo, and AS/NZS/ISO standards.
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AIMS Drill Bit Selection Guide: Choose by Material, Application & Cost
A practical guide to selecting the right drill bit for the workpiece you're cutting. Covers HSS, cobalt HSS, solid carbide, carbide-tipped, masonry, tile and glass drill bits, plus jobber, stub, step and SDS sub-types. Includes drill point geometry, coatings, brand selection across Sutton Tools, Bordo and P&N, and AS/NZS/ISO standards relevant to Australian industry.
Read moreThread Restoration Tools Guide: Die Nuts, Chasers, Files & Restorer Kits — When to Use Each
Thread restoration tools clean and reform damaged threads on bolts, studs, threaded rod and inside threaded holes — without removing parent metal. They are the AU mechanic's daily-driver tool for cleaning rusted wheel studs, the restorer's tool for refreshing original threads on classic car hardware, the maintenance fitter's tool for clearing road grime and corrosion from machinery threads, and the right answer when a tap-and-die set would remove too much material. This guide covers the four product families — die nuts (the entry-level workhorse), thread chasers (premium kits), thread files (multi-pitch hand files) and thread restorer kits (comprehensive metric+SAE) — the critical distinction from tap-and-die, the Lang Tools OEM-of-OEMs story, and the Sutton + Goliath + Bordo + Lang Tools range at AIMS — grounded in 16+ forum-validated insights from Practical Machinist, Garage Journal, Grassroots Motorsports and AU automotive forums. AIMS Industrial stocks 45 thread restoration products across 6 brands — the deepest supply across the entire Sutton brand series. Sutton Tools dominates die nut supply with 10 SKUs (AU patriot, Thomastown VIC). Goliath covers thread files plus die nut sets (14 SKUs total). Bordo provides the value chrome-alloy die nut range (8 SKUs). Lang Tools is the premium kit specialist (10 SKUs — and the actual OEM behind every Snap-On/Mac/Matco/Cornwell/Craftsman thread chaser kit). See the Thread Chasers collection. What is thread restoration — and how it differs from tap-and-die Thread restoration is the process of cleaning and reforming damaged external or internal threads without removing parent metal. The damage usually comes from one of four sources: Corrosion and rust — exposed bolts on chassis components, exhaust manifolds, suspension hardware. The thread profile is still intact but covered in oxide layers that prevent the nut running on. Mechanical damage — burrs from cross-threading, dings from impact, minor flattening from over-torquing. The thread crest deformed slightly but the thread root is intact. Paint, sealant or contamination — overspray on factory hardware during restoration, dried thread-locker residue, road grime, sealant overflow. Bolt/stud stretching damage — slight thread profile distortion from extreme torque or thermal cycling. In all four cases, the original thread is recoverable. Thread restoration tools reform and clean the existing thread profile. A tap-and-die set, by contrast, cuts material away to create a fresh thread — which removes some of the original parent metal and makes the thread loose if not used carefully. This is the single most-asked question in the cluster: "thread chaser vs tap" generates 20+ AU monthly searches by itself. The forum-validated answer from Garage Journal: "A tap can remove material and make the threads loose, while a chaser just reforms the thread and cleans out anything that shouldn't be there." The four thread restoration product families AIMS stocks four distinct product families across the thread restoration category. Knowing which tool fits which job is the difference between a clean restoration and a damaged thread: Product family Best for Price tier AIMS supply Die nuts External threads — bolts, studs, threaded rod. Entry-level, single-size hexagonal nut spun on with a spanner Lowest 28 SKUs (Sutton, Goliath, Bordo) Thread chasers External or internal threads — production kit format with multiple sizes. Mechanical reform geometry Mid 12 SKUs (Lang Tools premium, Draper BSPT specialty) Thread files External threads, light damage and burrs. Multi-pitch hand file with 4 sides of different pitches Mid 4 SKUs (Goliath specialty) Thread restorer kits Comprehensive multi-size workshop kits — Metric + SAE in one case. Internal and external coverage Highest 9 SKUs (Lang Tools) Most workshops end up owning multiple families: a Sutton die nut set in the most-used thread standard, a thread file for in-field cleanup, and a Lang Tools restorer kit for full coverage when needed. Die nuts — the entry-level workhorse A die nut is a hexagonal hardened steel nut with thread-cutting teeth on the inside. You spin it onto a damaged bolt or stud with a spanner. The hardened teeth reform the thread profile, clear corrosion and burrs, and produce a clean thread that a regular nut can run on smoothly. Die nuts are the most common entry point to thread restoration in AU workshops. Reasons: Cost — a single die nut is cheap; a basic 16-piece Metric set is affordable for any mechanic. Simplicity — a standard spanner is all you need. No die stock, no die holder, no special tool. External thread focus — covers the most common damage scenario (rusty bolts, dirty studs). Wide standards coverage — Metric (coarse and fine), UNC, UNF, BSW, BSF, BSP, BSPT, BSPF, Whitworth, NPT all available. Die nut vs button die vs split die — the geometry distinction: Die nut (hex die): Hexagonal, used for restoring/chasing existing threads with a spanner. Cannot cut new threads (the geometry is unforgiving — no progressive cut). Restoration tool only. Button die: Round circular die held in a die stock (round handle). Has a cutting taper and a finishing section. Cuts new threads — part of a tap-and-die set. Split die: Round circular die with a split for adjustment in a die stock. The split allows the die to be expanded slightly for an undersize cut (rough pass) then closed for the final cut. Cuts new threads — premium tap-and-die. This is the critical distinction — if you spin a die nut onto an intact thread, it cleans and chases. If you try to spin a die nut onto a bare un-threaded rod expecting it to cut new threads, it won't work. Use the right die for the job. Die nut sizing by thread standard Die nuts are sold by thread spec — diameter and pitch. The AU workshop standards covered at AIMS: Standard Typical use AIMS Sutton SKUs AIMS Goliath / Bordo SKUs Metric Coarse Most modern AU automotive, machinery, fasteners Sutton M440 Metric + 16-piece Metric Set Goliath EDN624C M6-M24 set + Bordo Chrome Alloy Metric Fine Bearing housings, precision components, fuel system fittings Sutton M441 Metric Fine Bordo Metric Fine UNC (Unified Coarse) American automotive (Falcon, Mustang, classic American iron), agricultural machinery Sutton M445 UNC + 10-piece UNC Set Goliath EDN141F set + Bordo Chrome Alloy UNF (Unified Fine) American automotive engine internals, aerospace, precision fasteners Sutton M446 UNF + 10-piece UNF Set Bordo Chrome Alloy BSW (British Standard Whitworth) British and Australian pre-1960 vehicles, vintage motorcycles (Triumph, BSA, Norton), classic restoration Sutton M447 BSW Bordo BSW Chrome Alloy BSF (British Standard Fine) British classic vehicles fine threads, vintage motorcycle engines Sutton M448 BSF Goliath EDN141B BSF Set + Bordo BSF Chrome Alloy BSP (British Standard Pipe, parallel) Plumbing fittings, hydraulic fittings, compressed air fittings - Goliath EDN181BSP Set BSPT (British Standard Pipe Taper) Pressure pipe fittings, hydraulic, gas (AU plumbing reg requirement) - Goliath EDN181BSPT Set BSPF (British Standard Pipe Female) Mating BSP fittings, female-thread cleanup Sutton M452 BSPF Bordo BSPF Chrome Alloy NPT (US National Pipe Taper) American hydraulic and pneumatic fittings, imported machinery - Goliath EDN181NPT Set + Goliath NPT singles For the workshop covering everything in one purchase, the Goliath EDNULTIM "Ultimate" Die Nut Set is the most comprehensive single SKU at AIMS — covers the broadest range of standards in one carded set. For Metric-only AU shops, the Sutton M454SDN1 16-piece Metric Set is the AU patriot workshop default. For die nut adapters that convert button-die geometries to die nut format (when restoring vintage tooling), see the Goliath Button Die to Die Nut Adaptor Set. Thread chasers — production kit format Thread chasers are the next tier up from die nuts — typically sold in production kits that cover multiple sizes in a single fitted case. The chaser itself works the same way as a die nut (reforms threads without removing parent metal), but the kits are designed for professional automotive workshop and tool truck distribution. The Lang Tools OEM story — the AU buyer-guide centrepiece This is the most-cited fact across AU and US thread restoration forums, and it's worth knowing before you spend tool-truck money: Lang Tools is the OEM for virtually every premium-branded thread chaser kit. Direct forum quote from Garage Journal: "Virtually every single thread chase tool set sold today is made by Lang Tools. SnapOn, Mac, Matco, Cornwell, Craftsman, Kastar, etc. are all made in USA by Lang Tools and then rebranded and upcharged by others." A Lang Tools 48-piece kit typically sells for around workshop-tier pricing. The same physical kit rebadged as Snap-On costs three to four times the price. Identical product. Same factory. Different sticker. This is why AIMS stocks Lang Tools directly. AU mechanics and tradies get the production-grade kit without the tool-truck mark-up. The Lang Tools range at AIMS: Lang Tools 48-Piece Metric and SAE Kit — the workshop comprehensive kit. Same physical product as the Snap-On equivalent at a fraction of the price. Lang Tools 26-Piece Fine and Coarse SAE Kit — for American iron and classic restoration work. Lang Tools 15-Piece Metric Kit — modern AU automotive default. Lang Tools 6-Piece Metric Tap Restorer Set — internal thread restoration in a tap format. Lang Tools 6-Piece UNC Tap Restorer Set — internal UNC thread restoration. Lang Tools Spindle Rethreader Kit, 8 Pieces (Metric + Imperial) — wheel stud / axle thread restoration specialty. Plus 4 individual Lang Tools restorer files (LG2573 3-piece set, LG2665 / LG2666 Imperial, LG2670 Metric). Draper BSPT specialty chasers For BSPT (British Standard Pipe Taper) specifically — common on AU plumbing and hydraulic fittings: Draper Imperial BSPT Thread Chaser — single chaser Draper Imperial BSPT Thread Chaser with Holder/Guide — guided system for tapered pipe threads Thread files — multi-pitch hand files Thread files are hand files with cutting teeth machined to specific thread pitches. The standard design is a square-shank file with each of the four sides carrying teeth at a different pitch (typically 4–8 different pitches per file, covering the most common standards in that thread family). The operator selects the side that matches the damaged thread, presses the file teeth into the thread profile, and runs the file along the thread to reform and clean it. Thread files work best on: External threads only (the file wraps around the bolt) Soft to medium-hardness metals — mild steel, brass, aluminium, unhardened steel Light damage — burrs, dings, paint, light corrosion Field repair — when a die nut isn't available or the bolt can't be removed from the assembly Thread files struggle on hardened bolts (grade 8.8, 10.9, 12.9 — the file teeth aren't hard enough to cut hardened steel) and on severely damaged threads where significant material is missing. AIMS Goliath thread file range — the AU specialty pick, covers all major thread standards: Goliath FILEMET Internal/External Metric Thread File — for modern AU automotive and machinery Goliath FILEUN Internal/External UNC/UNF Thread File — for American automotive and imperial fasteners Goliath FILEGAS Internal/External BSP Thread File — for plumbing, hydraulic, gas fittings Goliath FILEBSW Internal/External Whitworth Thread File — for British classic vehicle and vintage motorcycle restoration Internal vs external thread file geometry. The Goliath range covers both — internal thread file geometry is a round or tapered file with teeth on the curved surface, used to clean threads inside a tapped hole. External thread file is the standard flat-side multi-pitch format that wraps around bolts and studs. Thread restorer kits — comprehensive workshop coverage The largest thread restorer kits cover both Metric and SAE in a single case, with separate dies for each common thread spec. These are the workshop's "buy once, cover everything" option. The Lang Tools 48-piece kit is the comprehensive AU workshop standard. For workshop coverage logic: Mostly modern AU vehicles + machinery: Lang Tools 15-piece Metric kit. Covers the day-to-day work without paying for SAE you don't use. Mixed AU + American classic + heavy machinery: Lang Tools 48-piece Metric + SAE kit. The full-coverage option. American-only specialty: Lang Tools 26-piece SAE fine + coarse kit. Wheel stud and axle specialty: Lang Tools 8-piece Spindle Rethreader Kit. Designed for the spinning-on-the-spindle wheel stud restoration that other kits handle awkwardly. The Champion CTRT-1 Thread Restorer Tool is a specialty single-tool option for specific restoration jobs. Specialty thread chasers — spark plug, oxygen sensor, wheel stud Beyond the general-purpose die nut and chaser kits, three specialty thread chasers solve specific automotive workshop problems that come up often enough to warrant dedicated tools: Spark plug thread chasers The AU spark plug thread cluster is real — "spark plug thread chaser" generates around 70 monthly searches. The need: spark plug threads in aluminium cylinder heads get carbon-fouled, oil-contaminated, and over-torqued. A standard die nut won't fit (spark plug threads are typically 14mm × 1.25 metric, sometimes 18mm × 1.5, occasionally 5/8" × 18 UNF on older engines, often blind holes deep in the head). The fix is a long-reach spark plug thread chaser designed to clean the carbon and reform the thread without removing aluminium parent metal. Critical for engines like the AU Falcon BA-BF I6 (where the spark plug bores are deep set), Holden LS V8s, modern direct-injection engines with tight tolerances. Oxygen sensor thread chasers O2 sensors and AFR sensors thread into exhaust manifolds and catalytic converters at high temperature. After 5–10 years of thermal cycling, the threads are typically rusted, distorted from heat creep, and have crystallised exhaust residue baked into them. A standard die nut won't reach (exhaust manifolds have limited access) and standard cutting fluid burns off at exhaust temperature. O2 sensor specific chasers (M18 × 1.5 typically) are made for this access scenario. Common practitioner workflow: penetrating oil overnight, heat the manifold to about 150°C, chase the thread, fit the new sensor with anti-seize. Wheel stud rethreader kits Wheel studs get damaged from cross-threaded nut installation (impact gun on a tilted nut), curb strikes, and corrosion. Standard die nut works but is awkward to spin around a stud that's still mounted in the hub. The Lang Tools 8-piece Spindle Rethreader Kit is the production workshop solution — covers Metric and Imperial wheel stud sizes (M12, M14, 7/16", 1/2") in a format designed for in-place workflow on hub-mounted studs. AU vehicle thread standards quick map Which die nut do you need for which vehicle? The AU automotive reality: Vehicle category Dominant thread standard Recommended die nut set Modern Japanese (Toyota, Mazda, Honda, Subaru, Nissan post-1980) Metric Coarse + Metric Fine Sutton 16-piece Metric set + M441 Metric Fine singles Modern Korean (Hyundai, Kia) Metric Coarse + Metric Fine Sutton 16-piece Metric set Modern European (BMW, Mercedes, Audi, VW) Metric Coarse + Metric Fine Sutton + Metric Fine specialty bits AU-built modern (Falcon BA-FG, Commodore VE-VF, Ute) Predominantly Metric (engine internals sometimes UNF) Sutton 16-piece Metric + UNF supplement for engine work Classic American (Mustang, Camaro, Charger, Trans Am, El Camino) UNC + UNF Sutton 10-piece UNC + 10-piece UNF sets, or Lang Tools 26-piece SAE kit Vintage British (FX/FJ Holden, Morris, Austin, MG, Mini) BSW + BSF Goliath BSF set + Bordo BSW Chrome Alloy singles Vintage Japanese (pre-1970 Datsun, Toyota, Hino) JIS (functionally identical to Metric) Sutton Metric set Vintage motorcycle (Triumph, BSA, Norton, AJS pre-1970) BSF on engine, BSW on cycle parts, BSP on plumbing Goliath Whitworth thread file + BSW/BSF die nuts Heavy machinery, agricultural (older Massey, Case, John Deere, Caterpillar) UNC + UNF + Whitworth for vintage Lang Tools 26-piece SAE + Goliath Whitworth file Truck and trailer (heavy commercial) Metric + UNC + some Metric Fine for hub fittings Lang Tools 48-piece Metric+SAE kit Plumbing and hydraulic systems BSP + BSPT + occasional NPT (imported) Goliath BSP set + BSPT set + Draper BSPT chasers Thread restoration vs tap-and-die — when to use which The cluster's #1 question. The forum-validated decision matrix: Damage type Tool of choice Why Rust, dirt, paint, road grime on intact thread Die nut or thread chaser Cleans without removing parent metal — preserves the original thread fit Light burrs, cross-threading dings, dried sealant Thread file or die nut Reforms damaged thread crest without cutting away material Multiple minor damage points across multiple thread sizes Thread restorer kit Comprehensive coverage in one purchase Wheel stud / axle thread damage Spindle rethreader kit Designed for the spinning-on-the-spindle workflow Stripped or significantly damaged thread (multiple thread profiles missing) Helicoil / Recoil / TimeSert thread insert See our Stripped Thread Repair Guide — restoration tools won't recover missing material Need to cut completely new threads in an undrilled hole or unthreaded rod Tap-and-die set See our Tap & Die Guide — restoration tools cannot cut new threads Need to chase a thread but worried about over-cutting Thread chaser / die nut (NOT tap) Tap can remove too much material if not perfectly straight; chaser reforms without cutting For severely damaged threads where the parent metal is missing or stripped, see our Stripped Thread Repair Guide. When matching old Recoil part numbers to current RC kit codes, our Recoil thread repair part numbers cross-reference covers all 277 kits across the 2007, 2013 and 2023 catalogues. For cutting fresh threads from scratch, see our Tap & Die Cutting Threads Guide. Step-by-step thread restoration technique The standard procedure for any external thread restoration job: Identify the thread standard and pitch. Use a thread pitch gauge against the undamaged section of the thread. Common AU standards: Metric (M6, M8, M10, M12, M14, M16, M18, M20, M22, M24), UNC, UNF, BSW, BSF, BSP, BSPT, NPT. Get this wrong and you'll destroy the thread. Clean the workpiece. Wire brush rust and dirt off the thread first. The die nut or thread file will work harder if you ask it to chew through scale and dirt. Apply cutting fluid or thread lubricant. Reduces friction, extends tool life, gives a cleaner thread profile. See our Cutting Fluids Guide. Position the die nut or thread chaser squarely on the thread. Start it by hand on the undamaged section so it aligns with the existing thread. If it won't start by hand, do not force it — re-check the thread spec. Spin the die nut onto the thread with a spanner. Apply steady, even rotation. The die nut should feel firm but turnable. If it binds, back off, clean the thread, re-apply lubricant. Test with the mating nut periodically. The mating nut should run on smoothly without forcing. If it still binds, continue chasing. If the mating nut destroys it, you've gone too far — the thread is now undersize. Clean swarf after restoration. Metal filings from the chasing process must be wiped off. Galling and binding result if left. For thread files: identify the correct pitch side, align the file teeth with the existing thread pattern, push or pull lightly along the thread. Test with mating nut every 3–4 passes. Stop when smooth. Common mistakes — forum-validated Mistake Cause Prevention Used a tap instead of a chaser/die nut Tap cuts material away; can make threads loose if not straight Thread restoration tools reform, not cut. Buy the right tool. Wrong thread pitch identified M10 × 1.25 vs M10 × 1.5; UNF vs UNC; BSP vs BSPT Use a thread pitch gauge on the undamaged section before any restoration tool Forced die nut on damaged thread Didn't start by hand on undamaged section first Always hand-start; if it won't start, recheck the spec No cutting fluid Dry chase tool struggles, generates heat, dulls fast Apply cutting oil or thread lubricant before each use Tap used on hardened bolt HSS tap fails on grade 10.9/12.9 hardened steel For hardened bolts, use carbide chase tool or replace fastener Thread file on hardened bolt File teeth aren't hard enough to cut hardened steel Thread file works on softer fasteners — switch to die nut for harder grades Skipped Bunnings tier, bought Snap-On tool truck kit Paid $300 for same product as Lang Tools $80 Lang Tools is the OEM — same kit, fraction of the price Tried to cut new threads with a die nut Die nut geometry doesn't have progressive cut — for restoration only For cutting new threads, use a button die in a die stock (see Tap & Die Guide) BSP die nut on BSPT thread BSP is parallel, BSPT is tapered — different geometry Verify whether the original thread is parallel or tapered before choosing the chase tool Wheel stud over-restoration Restored stud now undersize, wheel nut won't seat Test fit the mating nut frequently; stop as soon as it runs smoothly AU brand reality — Sutton + Goliath + Bordo + Lang + Draper + Champion at AIMS AIMS Industrial stocks 45 thread restoration products across 6 brands — the deepest supply across the Sutton brand series. The supply ladder: Sutton Tools (AU patriot, Thomastown VIC) — 10 die nut SKUs Sutton dominates the die nut category at AIMS with 10 SKUs covering Metric, Metric Fine, UNC, UNF, BSW, BSF, BSPF in individual carbon steel die nuts plus three multi-piece sets. The 16-piece Metric set is the AU workshop default; the 10-piece UNC and 10-piece UNF sets cover American iron and imperial work. Goliath (Goliath cutting tools, AU industrial) — 10 die nut SKUs + 4 thread files Goliath provides the most comprehensive die nut SET coverage — Metric Coarse, BSF, UNF, BSP, BSPT, NPT sets plus "The Ultimate Die Nut Set" covering everything in one carded pack. Plus the unique Button Die to Die Nut adaptor for vintage tooling restoration. The thread file range (FILEMET, FILEUN, FILEGAS, FILEBSW) covers all major standards in the multi-pitch hand file format. Bordo (AU value, Castle Hill NSW) — 8 die nut SKUs Bordo provides the value-tier chrome-alloy die nut range. Same thread spec coverage as Sutton (Metric, Metric Fine, UNC, UNF, BSW, BSF, BSPF, BSPT) at workshop-friendly pricing. Lang Tools (USA, the OEM-of-OEMs) — 10 premium kits and files Lang Tools is the actual manufacturer behind Snap-On, Mac, Matco, Cornwell, Craftsman and Kastar thread chaser kits. AIMS stocks Lang Tools directly — same product, mark-up-free. The 48-piece Metric + SAE kit is the comprehensive workshop pick; the 26-piece SAE kit is American iron specialty; the spindle rethreader kit is the wheel stud / axle specialty. Draper (UK, BSPT specialty) — 2 SKUs Draper covers the BSPT (British Standard Pipe Taper) specialty for AU plumbing, hydraulic and gas fitting work. Single chaser + chaser with holder/guide for the production format. Champion (specialty restorer tool) — 1 SKU The Champion CTRT-1 is a specialty thread restorer tool for specific applications. Honest scope — brands NOT stocked at AIMS The international thread chaser market includes premium tool-truck brands AIMS does not stock: Snap-On, Mac Tools, Matco, Cornwell, Craftsman (USA) — premium-branded tool truck kits. Same physical product as Lang Tools (Lang is the OEM). 3-4x the price for the rebadge. Kastar (USA) — Lang Tools rebrand under another name. ARP (USA) — performance specialty thread chasers. Hanson, Irwin (USA) — general-purpose thread chasers. Toledo (AU) — AU general tool range with thread file options. For these brands, source through our supplier network — call (02) 9773 0122 or use the contact form with your spec. Thread restoration selection checklist Before buying, run through this 8-point checklist: Identify the thread standard. Metric / Metric Fine / UNC / UNF / BSW / BSF / BSP / BSPT / NPT / Whitworth — verify with a thread pitch gauge. External or internal threads? External = die nut, thread chaser, thread file. Internal = thread tap restorer (Lang Tools 6-piece sets) or specialty restoration tool. Volume of work. Single bolt = single die nut. Multiple sizes = Sutton 16-piece Metric set or Goliath "Ultimate" set. Production / mixed workshop = Lang Tools 48-piece kit. AU automotive only, AU + American, or specialty pipe? Modern AU = Metric. American classic = SAE/UNF/UNC. Pipe = BSP/BSPT/NPT. Vintage British = BSW/BSF. Severity of damage. Light burrs/rust = thread file or die nut. Moderate damage = thread chaser. Severe / stripped = Helicoil (different tool family). Cost vs frequency. One job = buy single die nut. Repeated work = invest in a kit. Production workshop = Lang Tools comprehensive kit pays back fast. Wheel stud / axle specialty? Lang Tools 8-piece Spindle Rethreader Kit is purpose-built for the workflow. Pipe threads specifically? Draper BSPT chasers + Goliath BSP/BSPT/NPT die nut sets cover this specialty cleanly. Frequently Asked Questions Is a die nut a thread restorer? Yes. A die nut is the most common type of external thread restorer — a hexagonal hardened steel nut with thread-cutting teeth on the inside that you spin onto a damaged bolt with a spanner to clean and reform the thread. Die nuts work on external threads (bolts, studs, threaded rod) and are designed for restoration only, not for cutting new threads. What is the difference between a die nut and a regular die? A die nut is hexagonal and used with a spanner for thread restoration — it cannot cut new threads. A regular split die or button die is round, held in a die stock (round handle), and used to cut fresh threads in a tap-and-die set. Same family of tools, different jobs. Die nuts have unforgiving cutting geometry — they reform threads cleanly but cannot progressively cut new ones. What is the difference between a thread chaser and a tap? A tap cuts material away to create new threads. A thread chaser reforms the existing thread without removing parent metal. Use a tap to create new threads in an undrilled hole. Use a chaser to clean dirt, rust, paint or minor damage from an existing thread. Forum-validated: "A tap can remove material and make the threads loose, while a chaser just reforms the thread and cleans out anything that shouldn't be there." Why is Lang Tools recommended over Snap-On thread chasers? Because Lang Tools is the actual manufacturer of every Snap-On, Mac, Matco, Cornwell, Craftsman and Kastar thread chaser kit. They're the OEM. Direct Garage Journal forum quote: "Virtually every single thread chase tool set sold today is made by Lang Tools." The same 48-piece kit sells as Lang Tools for workshop-tier pricing and as Snap-On for three to four times the price. Same factory, same product, just a different sticker. AIMS stocks Lang Tools direct — no tool-truck mark-up. Can I use a die nut to cut new threads? No. Die nuts are designed for thread restoration only — their geometry doesn't include the progressive cutting taper needed to start fresh threads in unthreaded material. For cutting new threads, use a button die (round, in a die stock) or a split die — both available in a proper tap-and-die set. See our Tap & Die Cutting Threads Guide. What thread standard die nut do I need for my Australian car? Modern AU vehicles (post-1970) are predominantly Metric — bolts/studs are M6 to M24 with coarse pitch dominating. Some specialty fittings (bearings, fuel system) use Metric Fine. American imports and classics (Falcon V8, Mustang, Camaro, Charger, etc.) use UNC / UNF. Pre-1960 British vehicles (Holden FX/FJ era, Morris, Austin, MG, Triumph motorcycle) use BSW / BSF. Vintage motorcycle engines often use BSF or BSW. For modern AU automotive workshop coverage, the Sutton 16-piece Metric set covers the daily-driver range. What is the difference between BSP, BSPT and BSPF? BSP (British Standard Pipe, parallel) is the standard pipe thread for plumbing and pneumatic fittings — both mating threads are parallel. BSPT (British Standard Pipe Taper) has tapered threads on the male side, designed for pressure-sealing applications (hydraulic, gas) where the taper creates a seal. BSPF (British Standard Pipe Female) is the female counterpart to BSP — the female-thread cleanup tool. AU plumbing and hydraulic work uses all three; identify whether the original is parallel or tapered before choosing the chase tool. Can a thread file fix a stripped bolt? Only if the strip is minor — light burrs, cross-threading dings, or surface damage to the thread crest. If the thread profile has significant parent metal missing (multiple thread crests gone, holes through the side of the thread), neither a file nor a chaser will recover it. For severely stripped threads, you need a thread insert (Helicoil, Recoil or TimeSert) — see our Stripped Thread Repair Guide. Thread files work on undamaged-but-dirty or lightly-damaged threads. What is a spindle rethreader kit used for? A spindle rethreader kit is specifically designed for wheel stud and axle thread restoration. The geometry differs from a standard die nut to handle the workflow of restoring threads on a spinning axle or a wheel stud that's still mounted in the hub — where you can't easily get a standard spanner around a hex die nut. The Lang Tools 8-piece Metric + Imperial Spindle Rethreader Kit covers wheel studs in most AU and American passenger vehicles and light commercial. Do I need cutting fluid when using a die nut or thread chaser? Yes. Cutting fluid reduces friction, extends the tool's life by 3–5x, and produces a cleaner thread profile. Use cutting oil (HSS-compatible), penetrating oil + cutting oil mix, or specialty thread cutting paste. WD-40 is a workshop substitute but not as effective. Dry chasing dulls the tool fast and can gall the workpiece. See our Cutting Fluids Guide. How do I identify thread pitch on a damaged thread? Use a thread pitch gauge on an undamaged section of the thread (typically the end of the bolt below the threaded portion, or further down the bolt where damage hasn't occurred). The gauge has fingers cut to standard pitches — try each one until the fingers fit perfectly into the thread valleys without gaps. Common AU pitches: M6 × 1.0, M8 × 1.25, M10 × 1.5, M12 × 1.75, M14 × 2.0, M16 × 2.0. UNC examples: 1/4" × 20 TPI, 3/8" × 16 TPI, 1/2" × 13 TPI. Verify before any restoration tool touches the thread. Can I use a die nut on a hardened bolt? Yes, but with limits. Standard carbon-steel die nuts (like the Sutton M440 range) work fine on grade 8.8 hardened bolts (most modern AU automotive fasteners). For grade 10.9 and 12.9 hardened bolts (engine main bearing caps, conrod bolts, ARP performance fasteners), HSS die nuts (Goliath EDN series) work better — the harder cutting teeth handle the harder workpiece. For extreme-hardness specialty bolts, replace the fastener rather than chase it. Are thread files only for external threads? No. Goliath's range covers both external and internal thread files. External thread files are flat-sided multi-pitch designs that wrap around bolts and studs. Internal thread files have a tapered or curved profile with cutting teeth designed to clean inside threaded holes. For the workshop covering both, Goliath FILEMET (Metric), FILEUN (UNC/UNF), FILEGAS (BSP) and FILEBSW (Whitworth) all carry the internal/external designation. What's the price difference between Lang Tools and Snap-On? Substantial. A 48-piece Lang Tools Metric + SAE kit typically sells in Australia for around workshop-tier pricing. The same physical product rebadged as Snap-On retails for three to four times the price through the tool truck. As confirmed across multiple AU and US automotive forums: same factory, same physical product, just a different sticker. AIMS stocks Lang Tools direct so AU mechanics get the production-grade kit without the rebadge mark-up. Where do I buy thread restoration tools in Australia? AIMS Industrial stocks 45 thread restoration products across Sutton Tools (10 die nut SKUs — AU patriot), Goliath (10 die nut sets + 4 thread files), Bordo (8 die nut SKUs — AU value), Lang Tools (10 premium kits and files — the OEM of Snap-On/Mac/Matco), Draper (2 BSPT specialty) and Champion (1 specialty). See the Thread Chasers collection. For Snap-On, Mac, Matco, Cornwell, Craftsman, Kastar, ARP or other specialty brands, source through the supplier network on request. Need the right spanner for that bolt? Our Spanner Size Chart lists every common metric and imperial size. Cross-reference our Tap Types guide when picking between taper, plug, bottoming, gun and spiral flute taps.
Read moreNC Spotting Drill Guide: Sizes, Angles & Pre-drilling
NC spotting drills create precise centring spots that prevent twist drill wander on CNC machining centres. They are the first tool in the drilling sequence for every accurate hole on a CNC mill — a 0.5mm wander from a drill without a spot becomes a positional tolerance failure on the inspection report. This guide covers the 90° vs 120° vs 142° point angle selection rule (the universal "matching the following drill's point" principle), DIN 1897 vs DIN 333 (the spotting drill vs centre drill disambiguation), HSS cobalt vs VHM solid carbide with AlCrN coating, CNC speed and feed by material, and the AIMS Sutton + Bordo range — grounded in 18+ forum-validated insights from Practical Machinist, Hobby-Machinist, Home Shop Machinist BBS and CNCCookbook. AIMS stocks 10 NC spotting drill products. Sutton Tools dominates 9:1 with the deepest range of any product in our Sutton brand series — from cobalt HSS TiN workshop tier (D175 90°, D176 120°, plus 4-piece and 5-piece sets) through to VHM solid carbide premium CNC tier (D355 90°, D364 90° AlCrN, D365 142°, D365 142° AlCrN). See the Spotting Drill Bits & Sets collection. What is an NC spotting drill — and why every CNC job starts with one An NC spotting drill (also called a spot drill or NC spot drill) is a short, rigid drill bit designed to create a small conical depression at the precise location where a follow-up drill bit will enter the workpiece. The "NC" prefix indicates the tool is intended for Numerical Control (CNC) machining centres rather than manual lathe centre work. The reason every accurate CNC drilling job starts with a spotting drill: standard twist drills wander when they first contact a workpiece. The drill point cannot resist sideways force well, so the bit drifts in the direction of any flat, hard spot or surface imperfection — 0.2 to 0.5mm of wander on a 6mm drill is typical. On a positional tolerance of ±0.1mm, that's a fail. The spotting drill creates a centred conical pocket the following drill seats into, fixing the hole location before the wandering force can act. Spotting drills are short — typically 30–60mm overall length — which makes them rigid. The short flute length combined with the larger shank diameter gives them resistance to deflection that a long jobber drill simply cannot match. They cut only 1–3mm deep into the workpiece — just enough to create a registration cone, not a hole. Spotting drill vs centre drill — the DIN 1897 vs DIN 333 disambiguation The most-asked question in CNC machining tooling: what's the difference between a spotting drill and a centre drill? They look similar at a glance, but they are different tools for different jobs. Property NC Spotting Drill (DIN 1897) Centre Drill (DIN 333) Designed for CNC machining centres, hole-start centring before drilling Lathe tailstock support, creating a 60° centre in workpiece end face Geometry Single conical point — 90°, 120° or 142° included angle Combined drill-and-countersink — small pilot point + 60° countersink shoulder Cutting depth 1-3mm shallow centring spot Deep enough to seat a lathe centre (typically 3-15mm) Standard DIN 1897 DIN 333 (Form A, B, R) / ANSI B94-11 Length Short and rigid (30-60mm typical) Short but with characteristic stepped pilot geometry Use case Production CNC drilling — start every hole with a spot Lathe work — support workpiece between centres Typical material 5% or 8% cobalt HSS, or solid carbide (VHM) HSS or cobalt HSS — carbide rare for centre drills Workshop reality: many shops use centre drills as spotting drills. It works, but it's a compromise. Centre drills are designed for a different geometry (the 60° countersink follows a small pilot drill), and using one as a spot drill gives a less-clean centring cone than a purpose-built spotting drill. The follow-up twist drill can chatter on entry. The Practical Machinist consensus: if you're doing volume CNC work, buy proper NC spotting drills. If you have one centre drill on hand for the occasional spot, it'll do. For deep coverage of centre drills specifically — including the BS 328 / DIN 333 standards, lathe centre drilling technique, and the centre-drill vs combined-drill-countersink distinction — see our Centre Drill Bit Guide. The point angle decision — 90° vs 120° vs 142° Point angle is the most consequential decision when selecting an NC spotting drill. The choice depends on the drill bit that will follow the spot. Spotting drill angle Best for Why this angle Sutton SKU 90° Twin-purpose spotting and chamfering. Also for follow-up drills with <115° points Creates a 90° chamfer at hole entry. Two jobs in one tool — spotting + chamfering Sutton D175 90° HSS Cobalt TiN · Sutton D355 90° VHM · Sutton D364 90° VHM AlCrN 120° Production CNC default — when follow-up drill is standard 118° point Sits 2° wider than 118° drill — drill centre contacts spot bottom first, no chatter Sutton D176 120° HSS Cobalt TiN 142° For follow-up drills with 135-140° points (some imported and carbide drills) Sits 2-7° wider than 135-140° drill — same drill-centre-first principle Sutton D365 142° VHM · Sutton D365 142° VHM AlCrN The "118° drill = 120° spotting drill" rule The universal CNC convention: the spotting drill must have a LARGER included angle than the drill that follows. This sounds counter-intuitive, but the geometry is unambiguous. When a follow-up drill enters the spot, the drill's point must contact the bottom of the spot first — at the centre. If the spotting drill has a smaller (more pointed) angle than the follow-up drill, the drill's cutting lips contact the spot wall before the drill point reaches the spot bottom. The result is chatter, drill walk, and a sub-centred hole. By making the spot wider than the drill, the drill point reaches the centre of the spot before the cutting lips touch the wall. The drill seats cleanly, cuts true to centre, and the resulting hole is on-position. Follow-up drill point angle Correct spotting drill angle Typical drill type 118° 120° Standard HSS jobber drill, most workshop drill bits 135° 140° or 142° Split-point HSS or cobalt drill, carbide drill 140° 142° Some imported carbide drills Under 115° 90° Soft-material drills (timber, plastic) — also gives chamfer bonus Forum-validated practitioner direct quote from Practical Machinist: "Using 120 for a 118 drill gives less drill wear and more tool life with the drill that follows it, with less chatter at the entrance and better finish." The 2° margin is the workshop standard. The 90° exception — when chamfering matters. 90° spotting drills are used when the same operation should also chamfer the hole entrance (e.g. for tap entry, deburring, or socket-head cap screw seat). The 90° point creates a 45° chamfer at the hole edge. The trade-off is potential chatter when the follow-up drill enters (the 118° drill cutting lips can contact the 90° wall before the drill point reaches the centre). For production volume, 120° is preferred — for occasional work where chamfering saves an operation, 90° wins. HSS Cobalt vs VHM Solid Carbide — the cost vs performance decision Sutton's NC spotting drill range splits into two material families: cobalt HSS for the workshop tier, and VHM (Vollhartmetall — solid tungsten carbide) for the premium CNC tier. Property HSS Cobalt (5% or 8%) VHM Solid Carbide Best for Workshop CNC, mixed-material work, manual mills, hobby machining Production CNC, high-volume runs, hardened steel and stainless Cost 1x (baseline) 3-5x baseline Cutting speed Standard — runs at HSS feeds and speeds 2-3x HSS speed capability Heat tolerance Softens above ~600°C Stable to ~1000°C+ Brittleness Tolerant of imperfect setups, minor vibration Brittle — chips on chatter, side-load, or workpiece movement Manual mill use Suits manual machining Risk of chipping — needs rigid CNC setup Re-sharpenable Yes (specialist service) No — consumed Sutton SKUs D175 90°, D176 120° + 4pc and 5pc sets D355 90°, D364 90° AlCrN, D365 142°, D365 142° AlCrN The decision rule: for production CNC running mostly steel and stainless at standard feeds and speeds, VHM solid carbide is the right choice — the 3-5x cost is paid back through 2-3x cycle time reduction and longer tool life on demanding materials. For workshop CNC, manual mills, mould toolmaking and hobby machining, cobalt HSS is the practical pick — cheaper to replace when the geometry inevitably gets damaged, and tolerant of imperfect setups. Forum-validated practitioner reality from Hobby-Machinist: "Carbide spot drills are brittle on manual mills — they chip with the slightest chatter or workpiece movement. Cobalt HSS is the practical choice for non-CNC work." VHM brittleness is a real constraint, not a marketing point. Coatings — TiN vs AlCrN Sutton's spotting drill coatings split into two tiers: TiN (titanium nitride, gold finish) on the cobalt HSS series, and AlCrN (aluminium chromium nitride, dark grey/blue finish) on the premium VHM carbide series. TiN (titanium nitride) — entry premium coating. Increases surface hardness to ~2300 HV (vs ~700-900 HV uncoated HSS). Friction coefficient reduced. Standard for cobalt HSS spotting drills. Best for mild steel, free-machining steels, brass, aluminium. AlCrN (aluminium chromium nitride) — premium coating, optimised for elevated temperatures. Surface hardness ~3200 HV. Resists thermal degradation above 800°C — suits dry high-speed CNC cutting where thermal generation is a problem. Standard for the Sutton D364 and D365 AlCrN variants. Best for stainless steel, titanium, hardened steel, and dry-cut CNC. The choice between coated and uncoated, TiN and AlCrN, follows the production volume and material profile. Occasional shop use: uncoated or TiN. Daily CNC production in mixed materials: AlCrN. Stainless / hardened / dry cutting: AlCrN mandatory. Sizing for CNC work — diameter and depth NC spotting drills are available from approximately 3mm diameter up to 16mm. The diameter selection rule is straightforward: the spotting drill diameter should be slightly larger than the smallest hole diameter on the workpiece. A common production approach is to use a single spotting drill diameter (5mm, 6mm or 8mm depending on workshop standard) for all holes on a given component. Spotting drill diameter Best for Typical AIMS Sutton SKU coverage 3-5mm Small precision parts, electronics enclosures, mould components Within D175 / D176 ranges, smaller sets 6mm Workshop CNC default — covers most general parts D175, D176, D355, D365 single bits 8mm Production CNC default — covers most heavier parts D175, D176, D355, D364, D365 single bits 10-12mm Larger parts, heavy structural components D175, D176 larger sizes; D365 142° for matching carbide jobber drills Spotting depth. The forum-validated workshop default is 1/16" (1.6mm) for most production CNC. Some programmers reduce to 0.005" (0.13mm) — fingernail depth — for verification spots that confirm hole locations before the full job runs. Practical Machinist consensus: spot deeper than the chisel edge of the follow-up drill (typically 0.5-1mm) to ensure the drill point lands cleanly in the spotted cone. Set vs individual selection. Mixed-work shops typically buy the Sutton D1750004 90° 4-piece set, D175SDT5 90° 5-piece set, or D1760004 120° 4-piece set for one-stop coverage across diameters. Production shops with a single dominant diameter buy individual D175 or D176 bits in volume for replacement. Speed and feed — RPM by diameter, IPM by material NC spotting drill speeds and feeds depend on cutter diameter, material, and the cutter substrate (HSS cobalt vs VHM carbide). The table below consolidates manufacturer data and forum-validated practitioner figures. Material HSS cobalt SFM VHM carbide SFM Typical feed Mild steel (1018, 1020) 80-100 SFM 250-400 SFM 0.003-0.006 IPR Stainless 304 / 316 30-50 SFM 120-200 SFM 0.002-0.004 IPR (slower) Aluminium 6061 200-300 SFM 500-800 SFM 0.004-0.008 IPR Brass / bronze 150-250 SFM 400-600 SFM 0.003-0.006 IPR Hardened steel (35-45 HRC) Not recommended 80-150 SFM 0.001-0.003 IPR — VHM mandatory Cast iron (grey) 60-90 SFM 250-350 SFM 0.003-0.005 IPR — dry cut OK Practitioner reference figures. Forum-validated production speeds from Practical Machinist for general CNC spotting: 5/16" (8mm) VHM carbide spot drill in mild steel: 6,000 RPM at 5 IPM 5/16" VHM in stainless 304: drop to 4,000 RPM at 4 IPM with sulfur cutting oil 6mm HSS cobalt in mild steel: 2,000-3,000 RPM at 0.005 IPR feed Spotting depth: 0.062" (1.6mm) standard production default For broader cutting speed reference across all machining operations, see our Cutting Speeds and Feeds Chart. G82 dwell vs G81 — CNC programming for spot drills The CNC programming convention for spot drilling: use G82 (drill with dwell) rather than G81 (standard drill cycle). The dwell holds the spotting drill at the bottom of the spot for a fraction of a second, allowing the cutting edges to remove any high spots in the cone and producing a perfectly uniform chamfer geometry. Typical G82 dwell time for spot drilling: 0.1 to 0.5 seconds. The dwell: Ensures the spot reaches full programmed depth (chip evacuation completes) Produces a uniform chamfer around the hole edge (critical when the spotting drill doubles as a chamfer tool) Settles the spindle deflection — first-pass spots can be slightly off-centre from spindle dynamic deflection that the dwell allows to relax The "0.005" verification spot" trick. Forum-validated CNC programmer practice from Practical Machinist: when verifying a new program before committing to the full job, reduce the spotting depth to 0.005" (0.13mm) — fingernail depth. This creates a visible witness mark at every hole location. The operator can inspect the spotted workpiece against the drawing before committing to deeper spotting and drilling. Saves a damaged part if the program has a hole position error. The "do we still need pilot drills?" question Pilot holes — drilling a smaller diameter hole first before the final drill — used to be standard practice for any drill above ~6mm in steel. Modern split-point drills (especially in cobalt and carbide) have largely eliminated this need for everyday CNC work. Practical Machinist consensus: "Any CNC machine should drive a split-point drill into aluminium, mild steel, and annealed higher-strength steels up to 7/8"-1" diameter without a pilot hole." Modern drill geometry handles its own centring. Pilot holes are still justified in specific scenarios: Long inserted drills or spade drills without their own pilot — these have no self-centring point and benefit from a stub pilot Very deep holes (depth-to-diameter ratios > 5:1) where chip evacuation is the constraint Hand drilling without a spotting cycle — manual drill press work where wander is hard to prevent Very large diameters (above 25mm) where the cutting load is high and centring forces are critical For routine CNC drilling on a machining centre: spotting drill plus the final drill is the standard sequence. No pilot. The spotting drill does the centring work the pilot drill used to do. Materials — what each Sutton spotting drill is best for The Sutton range maps to specific material categories. Picking the right substrate and coating for the workpiece material matters more than picking a brand. Workpiece material Best Sutton SKU choice Why Mild steel (1018, 1020) D175 90° / D176 120° HSS Cobalt TiN Workshop tier — cost effective for general production, TiN coating sufficient Stainless 304 / 316 D364 90° VHM AlCrN / D365 142° VHM AlCrN AlCrN coating handles stainless's heat generation and work-hardening tendency Aluminium 6061 / 7075 D175 90° HSS Cobalt TiN (uncoated also OK) Aluminium is soft — VHM carbide overkill, HSS works at higher speeds Brass / Bronze D175 90° / D176 120° HSS Cobalt TiN HSS sufficient — match angle to follow-up drill Hardened steel (35-45 HRC) D355 90° / D365 142° VHM (with AlCrN for production) HSS will burn — VHM solid carbide mandatory Cast iron D175 / D176 HSS Cobalt TiN, or D355 VHM for production Cast iron dust is abrasive — TiN or VHM extends life Plastic / composite D175 90° HSS Cobalt TiN, run dry HSS is fine — slow speed, sharp edges critical Cutting fluid selection Spotting drill operations are short — 0.5 to 1 second at depth on most cycles. This makes cutting fluid less critical than for through-drilling, but the right fluid still extends tool life significantly. Air blast — fastest, no fluid handling. Standard for production aluminium and free-machining brass work. Flood coolant (water-soluble emulsion) — CNC machining centre default. 5-10% emulsion in water. Standard for steel, stainless, alloy steels. Through-spindle coolant (TSC) — premium CNC option. Coolant delivered through the spindle and out the cutter centre. Suits production VHM carbide work. Sulfur-based cutting oil — specifically for stainless 304/316 and difficult-to-machine alloys. Forum-validated practitioner standard for stainless spotting. Mineral cutting oil (general) — for manual mills running cobalt HSS spotting drills without flood coolant. Do not use water alone (flash-rusts the spot bottom on steel), WD-40 (burns off, not a cutting lubricant), or engine oil (viscosity wrong for high-RPM work). See our Cutting Fluids Guide for full workshop selection. Manual mills vs CNC machining centres — the VHM brittleness reality This is the single biggest setup-versus-tooling trap. VHM solid carbide spotting drills are designed for rigid, accurate CNC machining centres — they assume the spindle, fixture and workpiece are all moving in known controlled ways. Manual mills do not provide this. What kills VHM on manual mills: Chatter — quill deflection, belt drive vibration, workpiece resonance. VHM chips before it cuts. Side load — drilling off-perpendicular, accidentally moving the table during the cycle. VHM has no flexibility. Workpiece movement — a Kurt vise can flex 0.05mm under heavy clamp; that's enough to shatter a 6mm VHM spot drill on entry. Variable feed rate — manual quill feed is not constant. VHM wants smooth steady feed. The practical rule for manual mills: use cobalt HSS spotting drills. The Sutton D175 90°, Sutton D176 120° and the Bordo HSS Cobalt are all suited to manual mill use. They tolerate the imperfect setup that VHM cannot. For hobby CNC routers and small benchtop CNCs — the same rule applies. Sub-3HP spindles, polymer bed flex, less-than-perfect way alignment all contribute to setup imperfection that brittles VHM. Start with cobalt HSS; upgrade to VHM only if you've verified your setup is rigid enough. Common failure modes Failure mode Cause Prevention Spotting drill chips on entry VHM in non-rigid setup, workpiece moves on first contact Use cobalt HSS for non-rigid setups; verify fixture rigidity before VHM use Follow-up drill chatters when entering spot Spotting drill angle smaller than drill angle (90° spot + 118° drill) Match: 120° spot for 118° drill, 142° spot for 135-140° drill Hole position off after drilling Spot too shallow — drill point didn't reach centre of spot Spot at least 0.5mm deeper than follow-up drill chisel edge Spotting drill burns / blue tinge (HSS) RPM too high, no coolant, prolonged dry cut Stick to material-appropriate SFM table; ensure coolant or fluid flow Spot bottom not centred Spindle deflection, no G82 dwell Add 0.1-0.5 sec G82 dwell; check spindle runout VHM coating worn / dull Cut count exceeded, material harder than rated Replace; AlCrN-coated for stainless and hardened work HSS edges deformed Material harder than HSS (workpiece overheated, hard spot) Switch to VHM; check for material certification Programmer mis-set spot depth Multi-hole job, all spots at wrong depth Use 0.005" verification spot before committing to full job depth Stainless work-hardens before next pass Slow feed or dwell on stainless — work-hardens surface Maintain continuous feed; never dwell on stainless Spotting drill walks off centre Surface imperfection at start point; flat/scale spot Verify clean surface; consider light facing pass before spotting AU brand reality — Sutton 9:1 at AIMS, honest scope on imports AIMS Industrial stocks the deepest Sutton Tools NC spotting drill range of any Sutton brand category we've covered — 9 SKUs across cobalt HSS TiN and VHM solid carbide tiers, with 90°, 120° and 142° point angles. The Sutton range is comprehensive enough to be a single-brand workshop solution for AU CNC machining centres. Sutton Tools (AU patriot — 9 SKUs) Cobalt HSS TiN — workshop tier (5 SKUs): Sutton D175 90° Spotting Drill Bit, DIN 1897, Cobalt Steel, TiN — the workshop 90° default. For follow-up drills with point angles under 115°, or when chamfering is wanted. Sutton D1750004 90° Spotting Drill 4-Piece Set, 5% Cobalt HSS, TiN — 90° set covering common diameters in a single carded pack. Sutton D175SDT5 90° Spotting Drill 5-Piece Set, 5% Cobalt HSS, TiN — extended 90° set, broader diameter coverage. Sutton D176 120° Spotting Drill Bit, DIN 1897, Cobalt Steel, TiN — the workshop 120° default. For 118° follow-up drills. The most common production CNC spotting angle. Sutton D1760004 120° Spotting Drill 4-Piece Set, 5% Cobalt HSS, TiN — 120° set for shops standardising on 118° drills. VHM Solid Carbide — premium CNC tier (4 SKUs): Sutton D355 90° Carbide Spotting Drill Bit, VHM — solid carbide 90° for production CNC. Suitable for steel, stainless and harder materials. Sutton D364 90° Carbide Spotting Drill Bit, VHM, AlCrN coated — premium 90° with AlCrN coating. Best pick for production stainless and high-speed dry CNC work. Sutton D365 142° Carbide Spotting Drill Bit, VHM — solid carbide 142° for 135-140° follow-up drills. Sutton D365 142° Carbide Spot Drill, VHM, AlCrN coated — premium 142° with AlCrN. The top-tier pick for production CNC with carbide jobber drills. Bordo (AU value — 1 SKU) Bordo HSS Cobalt TiAlN Coated Spotting Drill Bit — value-tier alternative to the Sutton D175/D176. TiAlN coating offers similar thermal performance to AlCrN at lower cost. Honest scope — brands NOT stocked at AIMS The international NC spotting drill market includes premium specialty brands AIMS does not currently stock: Sandvik Coromant (Sweden) — global production CNC specialty premium Iscar (Israel) — production CNC specialty Garr Tool, Harvey Performance, OSG (USA / Japan) — US/JP production CNC premium Walter, Gühring, Fraisa (Germany) — European production CNC specialty Niagara Cutter, Helical Solutions (USA) — US machining centre specialty Mitsubishi Materials (Japan) — JP production CNC premium For these brands, we'll source through our supplier network — call AIMS on (02) 9773 0122 or use the contact form with your spec. AU CNC manufacturing — where Sutton spotting drills earn their keep The Australian CNC manufacturing sector is smaller than the US or European markets but technically demanding. Sutton Tools' Thomastown VIC manufacturing facility serves this sector directly, and the NC spotting drill range is one of Sutton's bread-and-butter product families for AU machine shops. Sectors using Sutton NC spotting drills in production: Aerospace and defence — Marand (Melbourne), BAE Systems (Williamtown), ASC (Adelaide naval shipbuilding) — precision machining of aluminium and titanium components requiring tight positional tolerances. AlCrN-coated VHM is the standard tooling. Mining equipment — Bisalloy steel processing, WesTrac Caterpillar component remanufacture, Komatsu service centres. Heavy structural component drilling on CNC machining centres. D175 90° and D176 120° cobalt HSS dominant for general production. Agricultural and earthmoving machinery — chassis and implement manufacture, often in mild steel and HSLA grades. Cost-effective HSS cobalt range standard. Mould toolmaking — plastic injection mould and die-casting mould production. Precision spotting of cooling channels, ejector pin holes, vent holes. Mix of HSS and VHM depending on mould steel hardness. Precision component manufacture — instrumentation, medical devices, electronics enclosures. D175 90° + smaller diameter sets dominant. Repair and maintenance shops — manual mill work on Bridgeport-style machines, where VHM brittleness is a real constraint. Cobalt HSS the standard pick. Sutton's competitive position: against Sandvik Coromant, Iscar, Garr, OSG and other international premium brands, Sutton competes on AU-manufactured origin, local technical support, and short supply chain. For Australian production shops doing volume work, Sutton's D175/D176 HSS cobalt range is the workshop-cost standard, and the D355/D364/D365 VHM range is the premium production tier — both available off-the-shelf at AIMS rather than imported lead-time. NC spotting drill selection checklist + common mistakes Before buying, run through this 8-point checklist: Identify the follow-up drill angle. Standard 118° HSS = 120° spot. Split-point 135° = 140° or 142° spot. Match the angle. Decide HSS Cobalt or VHM Carbide. Workshop/manual mill = HSS cobalt. Production CNC = VHM. Hardened steel/stainless production = VHM AlCrN. Pick the coating. Mild steel/aluminium/brass = TiN. Stainless/hardened/dry CNC = AlCrN. Both are sufficient for general workshop use. Diameter. Workshop default 5-6mm for general parts; 8mm for heavier work. Match to your smallest production hole. Set vs single. Mixed work = 4 or 5-piece set. Production with one dominant diameter = singles in volume. CNC programming. Use G82 dwell, not G81. Spot depth 1.6mm (1/16") standard, 0.13mm (0.005") for verification. Cutting fluid. Match to material. Stainless = sulfur cutting oil. Steel = water-based emulsion. Aluminium = air blast OK. Backup plan. Stock at least one matching pilot HSS bit in case the VHM tip chips mid-job. Top 10 forum-validated mistakes: Using a centre drill as a spot drill — works but compromises quality. Buy the right tool. Wrong point angle — 90° spot with 118° drill gives chatter. Match the geometry. VHM carbide on a manual mill — chips at the first vibration. Use cobalt HSS. Spot too shallow — drill doesn't seat in cone. Spot at least chisel-depth + 0.5mm. Spot too deep — wastes cycle time, no benefit beyond 1/16" for production. Standard is 0.062". G81 instead of G82 — no dwell means non-uniform chamfer. Use G82 with 0.1-0.5 sec dwell. Spotting in stainless without sulfur oil — work-hardens before next pass. Use sulfur-based cutting fluid. HSS in hardened steel — burns the cutting edges in seconds. Use VHM. Pilot drill plus spotting drill plus final drill — redundant for diameters under 7/8". Spot + drill only. Trying to chamfer with a 120° spot drill — produces non-standard 60° chamfer. Use 90° if chamfering required. Frequently Asked Questions What is an NC spotting drill used for? An NC spotting drill creates a small conical depression at the precise location where a follow-up drill bit will enter a workpiece on a CNC machining centre. The spot prevents twist drill wander — without it, a standard drill can drift 0.2-0.5mm from the intended hole location, which fails most positional tolerance specs. Every accurate CNC drilling job starts with a spotting drill. What is the difference between a spotting drill and a centre drill? A spotting drill (DIN 1897) is a single-conical-point tool used on CNC machining centres to create a centring spot for a following drill. A centre drill (DIN 333) is a combined drill-and-countersink used on lathes to create a 60° centre in the workpiece end face for tailstock support. Spotting drills come in 90°, 120° and 142° point angles to match follow-up drills; centre drills have a fixed 60° countersink for lathe centre fit. See our Centre Drill Bit Guide for the centre-drill deep-dive. Which point angle should I buy — 90, 120 or 142 degrees? Match the spotting drill angle to the follow-up drill point angle, with the spotting drill 2-7 degrees wider. Standard 118° HSS jobber drill = 120° spotting drill (Sutton D176). Split-point 135° cobalt or carbide drill = 140° or 142° spotting drill (Sutton D365). For occasional work or when chamfering is also wanted, 90° (Sutton D175 or D355) serves both jobs — spotting plus 45° chamfer at hole entry. Why does my drill chatter after spotting? Almost always because the spotting drill angle is smaller (more pointed) than the follow-up drill angle. A 90° spotting drill creates a 45° cone wall; a 118° drill's cutting lips contact the cone wall before the drill point reaches the centre, causing chatter. Fix: use a 120° spotting drill with a 118° follow-up drill. The spot needs to be wider than the drill. HSS Cobalt or VHM Carbide — which should I buy? VHM Solid Carbide for production CNC machining centres running mostly steel and stainless at standard or high feeds and speeds, where the 3-5x cost is paid back through 2-3x cycle time reduction and longer tool life. HSS Cobalt for workshop CNC, manual mills, mould toolmaking and hobby machining where setup rigidity is imperfect and VHM brittleness becomes a problem. Workshop reality: VHM chips on chatter, cobalt HSS tolerates it. What is DIN 1897? DIN 1897 is the German industrial standard for NC spotting drills — short, rigid drills with single conical points for CNC hole-start centring. It defines the diameter sizes, overall length, shank type and tolerance class. Sutton D175 and D176 are DIN 1897 compliant. The standard differs from DIN 333 (centre drills for lathe work) — two different products for two different jobs. What does VHM mean? VHM is the German abbreviation for "Vollhartmetall" — literally "full hard metal" — meaning solid tungsten carbide. The opposite is carbide-tipped (HSS body with carbide tips brazed on the cutting edges). VHM is more rigid, holds an edge longer, and tolerates higher cutting speeds than HSS or carbide-tipped tools, but is brittle and chips on impact or vibration. Sutton's D355, D364 and D365 are VHM. Sutton's D175 and D176 are HSS cobalt — not VHM. What does AlCrN coating do? AlCrN (aluminium chromium nitride) is a premium thin-film coating applied to cutting tools — particularly VHM carbide. It increases surface hardness to ~3200 HV and resists thermal degradation above 800°C. The coating is dark grey to blue in colour. Best for stainless steel, hardened steel and dry high-speed CNC cutting where thermal generation is a constraint. Sutton's D364 90° AlCrN and D365 142° AlCrN variants are the premium picks for production stainless work. Do I need a pilot drill before spotting? No. The whole point of using a spotting drill is to eliminate the need for a pilot. Modern split-point twist drills (HSS, cobalt or carbide) handle their own centring on diameters up to 7/8"-1" in steel and aluminium when started in a properly spotted hole. Pilot drills are only justified for very large diameters (above 25mm), very deep holes (depth-to-diameter > 5:1), or specialty long-inserted/spade drills without self-centring geometry. Should I use G82 dwell when spot drilling? Yes. G82 (drill with dwell) is the CNC programming standard for spot drilling. The dwell — typically 0.1 to 0.5 seconds at depth — ensures the spot reaches programmed depth, produces a uniform chamfer around the hole edge, and allows spindle deflection to settle for a centred cone bottom. G81 (standard drill cycle) without dwell can produce off-centre or non-uniform spots. How deep should I spot drill? The standard production CNC default is 0.062" (1.6mm or 1/16") deep. This is enough to create a registration cone for the follow-up drill while minimising cycle time. For verification spots (confirming hole locations before committing to the full job), reduce to 0.005" (0.13mm) — fingernail depth — which creates a visible witness mark without removing meaningful material. Spot at least chisel-depth + 0.5mm of the follow-up drill, ensuring the drill point lands inside the cone. What RPM and feed should I run a spot drill at? For a 5/16" (8mm) VHM carbide spot drill in mild steel: 6,000 RPM at 5 IPM (forum-validated CNC default). For 6mm HSS cobalt in mild steel: 2,000-3,000 RPM at 0.005 IPR. Stainless 304 needs to drop to 4,000 RPM or slower with sulfur cutting oil. Always use the SFM tables (80-100 SFM for HSS cobalt in mild steel; 250-400 SFM for VHM carbide) and apply your spindle's RPM equation. Can VHM carbide spot drills be used on a manual mill? Risky. VHM solid carbide is brittle — it chips with chatter, side load or workpiece movement. Manual mills (Bridgeport-style) introduce all three: quill deflection, manual feed inconsistency, and vise flex. Cobalt HSS is the practical pick for manual machining. Save VHM for rigid CNC machining centres. The Sutton D175 90° and D176 120° HSS cobalt range is the AU manual mill default. Why is Sutton not using DIN 1897 on the VHM range? DIN 1897 specifies cobalt HSS substrate. The Sutton D355, D364 and D365 are VHM solid carbide — outside DIN 1897 scope but still designed for the same NC spotting drill function. Sutton uses Sutton's own internal geometry specification for the carbide range, with the same 90° / 120° / 142° point angle options as the DIN 1897 HSS range. Functionally equivalent for the user — just different substrate and standard reference. Where do I buy NC spotting drills in Australia? AIMS Industrial stocks 10 NC spotting drill products — 9 Sutton Tools (D175 90°, D176 120°, D355 90°, D364 90° AlCrN, D365 142°, D365 142° AlCrN, plus 90° 4pc and 5pc sets and 120° 4pc set) and 1 Bordo (HSS Cobalt TiAlN). See the Spotting Drill Bits & Sets collection. For Sandvik Coromant, Iscar, Garr, Harvey Performance, OSG, Walter or Gühring, source through our supplier network on request. Cross-reference our Drill Bit Size Chart for the exact metric, fractional, letter or number drill you need. Looking for carbide drill bits? Our carbide drill bits range covers the common sizes and brands.
Read moreSpot Weld Drill Bit Guide: How to Use a Spot Weld Cutter
Spot weld drill bits: 6mm and 8mm sizing, hand vs swan neck vs revolver geometries, HSS cobalt vs TCT for UHSS and boron, centre punch technique, and Sutton + Bordo selection for Australian panel beaters and smash repair workshops.
Read moreAnnular Cutter Guide: Weldon Shank, Pilot Pins, Sizing & Magnetic Drill Cutter Selection
Annular cutters explained: 3/4 inch Weldon shank standard, pilot pin slug ejection, HSS vs TCT selection, RPM by diameter, depth-of-cut sizing 25 to 110mm, drill press adapters and forum-validated buying advice for AU fabricators.
Read moreCarbide Burr Guide: Shapes, Cuts & Applications
A carbide burr is a small rotary cutting tool with a tungsten carbide cutting head and a steel shank, designed to spin at high RPM in a die grinder, flex-shaft tool or pencil grinder. It cuts, shapes, deburrs and bevels metal, hard plastics, fibreglass and other tough materials by removing chips with rows of helical teeth — not by abrasion. Rotary burr, carbide bur, die grinder bit and tungsten carbide rotary file all describe the same tool family. This guide decodes carbide burrs from first principles: the ANSI B94.19 shape codes (SA through SN), single vs double vs diamond cut, the RPM-by-head-diameter chart that prevents broken teeth and wrist injuries, the aluminium chip-welding problem and three field fixes for it, and the brand reality at the Australian industrial trade tier. Coverage is built for the AU fitter, welder, fabricator, mining maintenance tech and mould-maker — not the consumer or hobby buyer. If you're doing edge work by hand with a Shaviv or Noga deburring blade, see our Deburring Tool Guide. This article is the power-tool counterpart — when the work is too coarse, too deep or too internal for a hand blade. What is a carbide burr and what is it used for? A carbide burr is a rotary cutter that removes material from metal, hard plastics and composites by cutting — not grinding. It has a tungsten carbide head fluted with helical teeth, brazed or solid-sintered onto a steel shank, and it spins between 10,000 and 90,000 RPM in a die grinder, flex-shaft tool or pencil grinder. Typical jobs include weld bead removal, weld bevel prep on cast iron and steel, internal port cleanup in cylinder heads and intake manifolds, deburring hard-to-reach edges, sculpting and engraving in dies and moulds, removing rust scale from fabrication weld zones, and smoothing rough oxy-cut or plasma-cut profiles. Tungsten carbide is roughly three times harder than high-speed steel and holds an edge at temperatures that would soften HSS. That's why carbide burrs cut hardened steel, stainless and cast iron — work that would dull or destroy a comparable HSS rotary file in minutes. AIMS stocks 234 carbide burrs across Pferd (German engineered, the universal forum gold standard), Sutton Tools (Australian manufacturer), Bordo (Australian value tier), Saber and Klingspor — browse the full range at /collections/burrs, plus dedicated burr sets for starter kits. Carbide burr vs HSS burr vs rotary file vs end mill The names overlap because the tools overlap — but four important distinctions separate them. Carbide burr vs HSS burr: HSS (high-speed steel) burrs cost less but lose their edge fast on anything harder than mild steel. Carbide holds its edge through stainless, hardened tool steel, cast iron and weld bead. For any production or trade workshop, carbide is the only realistic choice. HSS burrs survive only in light-duty hobby/wood scenarios. Carbide burr vs "rotary file": No real difference. "Rotary file" is the older industrial term (the burr was originally a powered version of a hand file); "carbide burr" describes the same physical tool. ANSI B94.19 — the US standard — calls them carbide burs; DIN 8033 (the German standard Pferd uses) calls them rotary tungsten carbide files. Same tool. Carbide burr vs end mill: An end mill is a precision milling cutter run in a CNC or manual mill spindle at low-to-moderate RPM, with rigid setup and coolant. A carbide burr is hand-held in a die grinder at very high RPM with no rigid setup. End mills have 2–6 flutes; burrs have 8–24+ teeth. Reddit r/CNC sums it up: "Burrs are nothing but crude endmills with many teeth, and often funny shapes convenient" for shaping work that doesn't need CNC-level precision. Carbide burr vs grinding stone / mounted point: A grinding stone removes material by abrasion (each abrasive grain is essentially a tiny chisel). A carbide burr removes material by cutting (each tooth peels a chip). Burrs cut faster than stones on most metals, leave a cleaner finish, and don't load up with metal swarf the way an abrasive stone does. Stones still win on extremely hard material (hardened tool steel above HRC 60) and on sharpening jobs. Tool Best for RPM range Notes HSS burr / rotary file Mild steel, brass, light deburring 3,000–20,000 Cheap; short life on hard material Carbide burr Steel, stainless, cast iron, weld bead, ports 10,000–90,000 (by head size) Workshop standard; primary tool End mill (in die grinder) Soft materials, aluminium edge work 10,000–25,000 "Climb cut leaves no burred edges" — Practical Machinist consensus on aluminium Mounted point / grinding stone Hardened steel, ceramic, sharpening 15,000–25,000 Abrasion not cutting; loads with swarf Flap wheel / sanding point Surface finish, blending 10,000–22,000 Finishing not removal Single cut vs double cut vs diamond cut vs microcut The single biggest selection decision is cut style. Get this wrong on aluminium and the burr clogs in seconds. Get it wrong on steel and the burr loads, glazes and dies. Double cut (the default) Double cut burrs have two helices of teeth running in opposite directions that intersect — the result is many small teeth and many small chips. Smoother finish, faster removal on steel, stainless and cast iron, and less aggressive feel than single cut. Default choice for ferrous work. Single cut Single cut burrs have one helix of teeth with no cross-cut. Fewer, larger teeth and deeper chip gullets. Result: bigger chips that clear faster — which is exactly what aluminium, brass, copper, bronze and soft plastic need. The forum consensus on r/Machinists captures it: "The burr one for nonferrous is single cut but has much fewer flutes, almost like an endmill." Single cut also wins on hard anodised aluminium and on edges where double cut chip-welds and dies. Diamond cut (aluminium cut / NCC) Confusingly named — diamond cut burrs have nothing to do with actual diamond. They are double-cut burrs with extra chip-breaker grooves cross-cut across the diameter of each tooth, producing tiny chip-breakers along every cutting edge. Aggressive stock removal on hardened steel and weld bead. Pferd's "diamond cut" (forum-described as "amazing" on Reddit r/Tools) is the production-tier example. NCC (Non-Ferrous Cut) / aluminium cut A specialised single-cut geometry with wide chip gullets and an aluminium-friendly tooth profile, sometimes paired with a non-stick coating. Pferd's NCC range, Sutton aluminium-cut burrs and dedicated "Aluminium Cut" sets from Renegade, Alpha and others all play here. If you cut aluminium more than occasionally, an NCC burr is the upgrade that ends chip-welding. Microcut Many fine teeth — used for precision finishing, mould detail work, deburring delicate parts and intricate engraving where surface finish matters more than removal rate. Pferd's microcut range is the forum-validated reference: r/Tools quote, repeated across 10+ threads, calls Pferd 1/8" microcut "mind-blowing compared to dremel brand." Cut style Best for Avoid on Finish Double cut Steel, stainless, cast iron, weld bead Aluminium (chip welds) Smooth, controlled Single cut Aluminium, brass, copper, soft plastic, hard anodised Hardened steel (under-engages) Coarser, fast clearance Diamond cut Hardened steel, weld bead, mill scale, aggressive stock removal Aluminium (chip welds badly) Coarse NCC / aluminium cut Aluminium production work, anti-clog Steel (designed for soft metals) Clean on aluminium Microcut Mould detail, finishing, precision deburring Bulk stock removal (slow) Fine ANSI B94.19 shape codes — SA, SB, SC, SD, SE, SF, SG, SH, SJ, SK, SL, SM, SN Every carbide burr from every reputable manufacturer follows the ANSI B94.19 shape code system (or its DIN 8033 European equivalent — the two standards align on shape codes). Once you know the code, you can pick the right burr for the work from any catalogue worldwide. Code Shape Profile Best for SA Cylindrical (plain end) Straight cylinder, no end teeth Flat surfaces, broad contours, side-cutting edge removal — the all-rounder SB Cylindrical with end cut Cylinder with cutting teeth on end face Edge chamfering, slotting, finishing flat bottoms SC Cylindrical radius end Cylinder with rounded nose Die work, blending flat into curved, no sharp corner mark SD Ball Spherical head Concave radii, deburring round features, hollowing, internal porting SE Oval (egg) Elongated sphere General contour work — forgiving, less gouging (r/metalworking favourite for aluminium) SF Tree radius end Tapered with rounded tip Weld prep on curves, rounding edges, contour blending SG Tree pointed end Tapered with sharp point Narrow corners, internal angles, precision detail SH Flame Curved teardrop Sculpting, tapered recesses, detail shaping, art metalwork SJ Cone 60° 60° included-angle cone Chamfering, large countersinks, V-grooves SK Cone 90° 90° included-angle cone Standard countersinking, chamfering bolt holes for flush flat-head fit SL Cone radius (taper) Tapered with rounded tip Smooth tapered cuts, curved transitions SM Cone pointed Sharp tapered point Sharp tapered profiles, V-grooves, point-detail work SN Inverted cone Wider at tip, narrower at shank Dovetail slots, gib blocks, undercut work, T-slot cleanup European catalogues sometimes use DIN 8033 codes (ZYA, ZYAS, WRC, KEL, KUD, RBF, SPG, FLM, KSJ, KSK, KEL, SKM, WKN). The shapes are the same — Pferd's catalogue cross-references both systems. Pferd's WRC = ANSI SC (cylindrical radius end); KUD = SD (ball); RBF = SE (oval); etc. Practical pick list if you're buying first burrs for a general workshop: SD (ball) — porting, deburring, internal radii. The single most-used shape. SC (cylindrical radius) — die work, weld prep on curved profiles, broad surface contouring. SA or SB (cylindrical) — flat work, side-cutting along a profile. SF or SG (tree) — internal corners, narrow access. SH (flame) — tapered recesses, sculpting. This is exactly the 5-piece set most AU burr sets ship in — Sutton B900SCB5, P&N Workshop, and most 5-piece kits cover SA + SC + SD + SF + SH. Shank diameter — 1/4 inch, 6 mm, 1/8 inch, 3 mm The shank size has to match your tool's collet. The two big traps: 1/4" vs 6 mm. 1/4" = 6.35 mm. 6 mm = 6.00 mm. They're not interchangeable. A 6 mm burr in a 1/4" collet sits 0.35 mm undersize and won't grip securely; a 1/4" burr in a 6 mm collet won't seat fully. Many AU die grinders use 6 mm collets (Trax, some Pferd-branded), while US tools and many trade-tier 1/4" tools use 1/4". Check your collet size before ordering burrs in bulk. 1/8" vs 3 mm. Same trap at smaller scale — 1/8" = 3.175 mm vs 3 mm = 3.00 mm. Pencil die grinders and Dremel-class tools use one or the other. Mismatched shanks slip and run out of true, which damages both the burr and the collet. Shank size Tool class Head diameter range Notes 3 mm metric Pencil grinder (Pferd, Dotco-class metric) 3–12 mm head European/metric workshops 1/8" (3.175 mm) Dremel-class rotary tools, flex-shaft, pencil air grinders 1/8"–3/8" head US and consumer-tier 6 mm metric 1/4"-class die grinders sold with metric collets 3–25 mm head Confirm collet before bulk buying 1/4" (6.35 mm) Standard industrial die grinder 1/4"–3/4" head Trade workshop default 3/8" / 10 mm Heavy-duty industrial die grinders 1/2"–1" head Foundry, mining, large weld prep Long-shank burrs (sometimes 150–200 mm overall length) are made for reaching into deep cavities — engine port work, internal tank cleanup, deep mould detail. Pferd's long-shank range and Sutton's L-series cover this. The trade-off is more flex and more vibration at high RPM; treat long-shank burrs gently. Head diameter and length — sizing the cutter to the work Head diameter (the cutting head's outer diameter) determines how aggressively a burr cuts and how fast it can safely spin. Head length determines how deep into a cavity it can reach. Standard imperial heads run 1/8", 1/4", 3/8", 1/2", 5/8" and 3/4". Metric heads run 3, 6, 8, 10, 12, 16 and 20 mm. The most common workshop sizes are 1/4" (6 mm), 3/8" (10 mm) and 1/2" (12 mm) heads — these cover 90% of fabrication and maintenance work. Length codes vary by manufacturer. Pferd and ANSI use head length classes: short (around the head diameter), medium (around 1.5× diameter), long (around 2× diameter) and extra-long for deep cavity work. AU listings will quote actual head dimensions: "12 x 25 mm" is a 12 mm diameter, 25 mm long head. RPM by head diameter — the safety-critical chart Maximum safe RPM drops as head diameter rises. Spin a 1/2" burr at 60,000 RPM and the teeth at the outer edge are travelling supersonic — they shed at unpredictable angles, the carbide chips, and the cracking sound that follows is the burr disintegrating. The forum reality: Reddit r/Machinists locksmith thread: "At that RPM, you might be causing too much vibration for the teeth to handle. Try cutting the speed in half." Safety first: Always check the burr's stamped or labelled max RPM. Manufacturers (Pferd, Sutton) print or stamp it on the shank. Never exceed the rated RPM. Cheap unbranded burrs without RPM markings should be treated as suspect — use them at the conservative end of the chart below. Head diameter Typical RPM range Max safe RPM Typical tool 1/8" (3 mm) 45,000–90,000 ~100,000 Dremel, pencil air grinder (Dotco 60,000 class) 1/4" (6 mm) 25,000–35,000 ~45,000 Standard 1/4" die grinder 3/8" (10 mm) 15,000–25,000 ~30,000 Standard die grinder, slowed for larger heads 1/2" (12 mm) 12,000–22,000 ~22,000 Industrial die grinder, throttled 5/8" (16 mm) 10,000–18,000 ~18,000 Heavy die grinder, low-speed setting 3/4" (20 mm)+ 8,000–15,000 ~15,000 Heavy-duty industrial only Forum-validated reality from r/Tools: "Carbide burrs like to be spun at 10–25k. The M12 die grinder will stall if you are trying to run it at a low speed and apply too much pressure." Modern variable-speed cordless die grinders (Milwaukee M12/M18, Makita 18V, AEG) let you dial the right speed for the head; pneumatic die grinders rely on regulator pressure. What tool to use a carbide burr in The right host tool for a carbide burr is a die grinder — pneumatic or cordless 18V/12V — with a 1/4" or 6 mm collet for full-size burrs, or a pencil die grinder with a 1/8" or 3 mm collet for fine burrs. Die grinder (straight / inline) The standard host. Pneumatic die grinders run 18,000–25,000 RPM unloaded with 90 psi air, cordless 18V die grinders run 8,000–25,000 RPM variable-speed. AIMS stocks Trax pneumatic die grinders, Pferd air grinders, and Metabo electric die grinders — see our Air Tools & Pneumatic Tool Guide for the full tool-selection rundown. Angle die grinder Right-angle head — useful for reaching into tight cavities at 90° to the tool body. But Reddit r/MilwaukeeTool consensus: "Carbide burrs are nice but those are more of a straight die grinder tool" — angle die grinders are best with cut-off wheels and flap discs, not burrs. The right-angle gear set adds vibration that shortens burr life. Flex-shaft tool Common in jewellery, gunsmithing, mould and die work. The motor sits above, a flexible drive shaft transmits rotation to a hand-piece with the collet. Lower max RPM than a die grinder (typically 20,000) but excellent precision and access. Pferd, Foredom and Dremel make industrial flex-shaft systems. Pencil die grinder Slim, lightweight, very high RPM (45,000–90,000) — the tool of choice for fine work and 1/8"/3 mm burrs. Dotco, Pferd PG, and Milwaukee M12 pencil grinders all play here. Drill chuck — the WRONG tool Don't run carbide burrs in a drill. Two problems. First, drills max around 2,500–3,000 RPM — far too slow for a carbide burr to cut efficiently; instead it grabs and tears. Reddit r/Tools sums it up: "Drills suck at die grinding, die grinders are too fast (even at)..." Second, drill chucks have measurable runout (eccentricity), and the side-loads from a burr accelerate chuck wear. The same thread documents Milwaukee drills going "noticeably sloppy" after carbide burr use. If you only have a drill, buy a die grinder before buying burrs — anything else is a false economy. Dremel and consumer rotary tools Dremel-class rotary tools (Dremel 4000, Ryobi rotary, Ozito) take 1/8" shanks and run 10,000–35,000 RPM. They handle small Pferd-microcut and 1/8" burrs fine for light work, but underpower for sustained stock removal on steel. r/Dremel direct: "If you are not familiar with burrs, I'd avoid that route" — burrs grab and the lightweight body can be hard to control. Workshop reality: buy a real die grinder for trade work. Aluminium and non-ferrous — the chip-welding problem The #1 forum complaint about carbide burrs is aluminium clogging. r/metalworking: "Aluminum loves to fill up carbide burrs and cause them to overheat (why they make aluminum specific burrs)." The chip welds itself between the burr teeth, blocks chip clearance, and the burr stops cutting and starts smearing — generating heat, ruining the workpiece surface and shortening burr life. Three fixes, in increasing order of effectiveness: Fix 1 — Use lubrication WD-40, paraffin wax, beeswax or dedicated aluminium-cut lubricants break the chip-weld cycle. Practical Machinist consensus: "Use a lube helps the burr cut instead of jumping. Something like LPS or Breakfree. WD-40 works will especially with aluminum." The r/metalworking workshop trick: "Grab a tea candle and wax the burr regularly" — drag the spinning burr against a candle every 30 seconds. Fix 2 — Switch to single cut Single-cut burrs have wider chip gullets that clear aluminium chips before they can weld. If you cut aluminium more than occasionally, keep a single-cut SD ball or SC cylindrical for non-ferrous work and a double-cut for steel — don't try to use one burr for both. Fix 3 — Use a dedicated NCC / aluminium-cut burr NCC (Non-Ferrous Cut) burrs are engineered for soft metals: single-cut geometry with extra-wide chip gullets, sometimes paired with a non-stick coating. Pferd NCC, Sutton aluminium-cut and dedicated kits from Renegade Industrial and Alpha all play here. If aluminium is daily work, the NCC upgrade ends the chip-welding problem entirely. Recovering a clogged burr If a double-cut burr is already gummed solid with aluminium, you can recover it. Practical Machinist (Cleaning Aluminum Buildup thread): "Get as much out as you can by chipping it out, then put the tool in a container of muriatic acid. Muriatic acid will dissolve the aluminum." Hydrochloric (muriatic) acid attacks aluminium but doesn't attack tungsten carbide. Submerge the head, wait 15–30 minutes, neutralise with water, dry thoroughly. Wear gloves and eye protection — muriatic acid is corrosive. Materials matrix — what burr for what metal Material Cut style Recommended shape Speed Notes Mild steel Double cut SA/SC/SD/SF Moderate The workshop default — any reputable double-cut burr handles mild steel Tool steel (annealed) Double cut SA/SC/SD Moderate Standard double cut, slightly slower feed Hardened steel (HRC 45+) Diamond cut or Pferd C3 Plus SC/SD Slow, light pressure Cheap carbide chips; trade-tier brand essential Stainless steel Double cut SA/SC/SF Slow Work-hardening — keep feed up, don't dwell. Premium carbide only Cast iron (grey) Double cut SA/SC/SD Fast Cast iron is brittle and burrs cut beautifully — the natural fit. Weld bevel prep is the classic job Cast iron (white) / Bisalloy / Hardox Diamond cut / Pferd hard cut SC/SD Slow Treat as hardened — chips smaller, slower removal Aluminium / soft non-ferrous Single cut or NCC SA/SC/SD/SF Moderate-fast NEVER double cut without lubrication — chip welds in seconds. NCC is the upgrade Brass / bronze Single cut SA/SC/SD Moderate Similar to aluminium — single cut clears chips Copper Single cut SA/SC Moderate Gummy — wax or oil mandatory Hard plastic / acetal / nylon Single cut or coarse cut SC/SD Moderate, low pressure Heat-sensitive — don't dwell or plastic melts and welds Fibreglass / CFRP composites Coarse cut (CFRP-specific) SA/SC Moderate Dust hazard — use respirator, vacuum extraction. r/CNC consensus: coarse cut prevents heat build-up Wood (general) Single cut or wood-specific carbide SD/SF Fast Hardwood, root carving, sculpting What carbide burrs won't cut well: Concrete, masonry, brick, tile — these are abrasive jobs for diamond-tipped tools (see angle grinder guide for masonry options). Tungsten carbide itself — you can't burr a tungsten-carbide part; only diamond cuts diamond, and only diamond cuts tungsten carbide effectively. Glass and ceramic — diamond burrs only. Applications — where carbide burrs earn their keep The hand-portable cutting reach of a carbide burr in a die grinder is unmatched for several classes of work that no other tool does well. Weld bead and weld bevel prep Removing weld spatter, blending weld beads flat, beveling cracks before re-welding (especially cast iron repair work — Practical Machinist quote: "I often use a carbide burr in a die grinder to bevel cracks for welding (usually grey cast iron)"). SC and SF shapes are standard for this work. Deburring (power deburring) When a hand deburring tool like a Shaviv or Noga blade can't reach — deep internal ports, blind holes, edges inside castings, complex profiles — a carbide burr in a die grinder is the power-tool alternative. Faster but harder to control. SD ball and SF tree shapes dominate this work. Engine port work and intake manifold smoothing Performance engine builders use carbide burrs to match port floor profiles to gasket templates, blend casting flash, polish intake runners, and smooth combustion chamber edges. Long-shank SD ball and SF tree burrs are the go-tos. AU dyno shops, motorsport workshops, marine and aviation maintenance all use this technique. Mould and die work Toolmakers and mould-makers use microcut carbide burrs (Pferd's microcut range is the gold standard) to detail injection moulds, dies, and forms — work that's too fine for a milling cutter and too coarse for hand stoning. Sculpting, engraving, art metalwork Industrial sculpting (custom bike work, hot-rodding, knife-making, blacksmithing finish work). SH flame and SG tree-pointed burrs dominate this work. Drill-out and lock removal Locksmiths use SD ball and SC cylindrical carbide burrs to drill out anti-theft locks. Reddit r/Locksmith and r/metalworking threads make this one of the most-cited burr applications. General fabrication cleanup Removing tack welds, rounding cut edges, beveling oxy-cut profiles before welding, smoothing plasma-cut edges, removing mill scale before paint prep. Climb cut vs conventional cut — direction matters Like end mills, carbide burrs cut differently depending on the direction you feed them relative to rotation. Climb cut (cut direction same as workpiece motion under the tool) leaves a cleaner edge with less burring — Practical Machinist quote: "I like a small (I use an ⅛" 60,000 rpm Dotco) die grinder with a carbide burr, climb cut. Very quick and leaves no burred edges." But climb cut can grab and run; controllable only with rigid setups or skilled hand control. Conventional cut (opposite direction) is more controllable, less grabby, and the standard for hand-held work. Slightly more raised edge to clean up after. For most hand-held die grinder work, conventional cut is safer. For finish work where edge quality matters most, controlled climb cut earns its place. Brand reality — Pferd, Sutton, Bordo, and the rest Carbide burr quality varies enormously. Premium brands hold their edge through full shifts; cheap import burrs chip on the first hard contact and shed teeth at high RPM. Brand Tier Origin Forum reputation AIMS supply Pferd Premium Germany The universal Reddit gold standard. Quoted across 10+ threads: "Pferd makes some of the best carbide burrs I've used. 1/8" microcut (mind-blowing compared to dremel brand) (1/4" diamond cut are amazing too.) Very pricey but..." ✓ 150 SKUs — full range, microcut, NCC, diamond cut, miniature shank, long shank Sutton Tools Trade premium (AU) Thomastown, VIC "I have bought a set Pferd brand carbides they're not the cheapest option but have been holding up well" — same tier in AU. Sutton B900 sets are the AU trade standard ✓ 34 SKUs — B100/B200/B201/B300 cylindrical, B900 sets, VHM solid carbide Bordo Trade value (AU) AU brand AU value-tier — Express Cut sets cover the workshop basics at trade pricing ✓ 24 SKUs — Express Cut sets, tree/radius/cylindrical, double cut Saber Trade value — Mid-tier value ✓ 15 SKUs — including 8020-S3 3-piece sets Klingspor Specialty Germany Better known for abrasives — burrs are a crossover line ✓ 5 SKUs P&N Consumer/retail AU Bunnings/Repco channel — limited industrial penetration 4 SKUs (AIMS limited) Noga Specialty (deburring) Israel Better known for hand deburring blades; small burr range ✓ 2 SKUs Garryson UK premium UK Forum-respected premium tier Not stocked — source on request HU-Friedy US specialty USA Dental-crossover, Practical Machinist favourite: "The brand HU FRIEDY is what I stick with. They are American made" Not stocked — specialty source Holemaker, Xtorque, Renegade Industrial, ATB Retail-trade branded Various Total Tools / Sydney Tools / TradeTools house brands — mid-tier Not stocked — see Total Tools / Sydney Tools Cheap unbranded import (1/8" multi-piece eBay/Amazon kits) Hobby/disposable China r/Tools "Die grinder carbide Burr chipping" thread documents quality variance — "depending on its quality, more or less chipped" Not stocked — buy local pro brands instead The trade-off: Premium burrs cost 3–5× the price of budget imports but cut faster, last longer (often 10–20× the life on production work), and don't shed teeth at speed. For one-off jobs the budget burr might survive; for daily use the premium burr is the only economic choice. Practical Machinist sums it up: "Get a carbide burr with large teeth along with a tool with the power to use it and you will have good results. If it is only lasting minutes or..." — undersized tool plus aggressive burr equals minutes of life. Burr sets vs individual burrs — what makes sense when For a starter workshop, a 5-piece set covering SA + SC + SD + SF + SH gives you the shapes that handle 90% of jobs. Sutton B900SCB5, P&N 5-piece, Bordo Express Cut 5-piece and Pferd 5-piece kits all play here. 10-piece sets add SB (cylindrical end-cut), SE (oval), SG (tree pointed), SK (90° cone) and SN (inverted cone) — the next-most-common shapes. Pferd 10-piece 1/4" shank sets and the Sutton B900 ten-piece kits cover this. 15- to 20-piece kits add length variants (short and long versions of the same shape), additional cone angles, and sometimes both single-cut and double-cut versions of common shapes. Useful for general engineering or contract fabrication work where job variety is high. Beyond ~15 pieces you're better off buying individual burrs as you need them. Reddit r/metalworking advice: "I don't buy them as a set, just a few shapes that I need for whatever I need at the time. Over time, they add up to a good selection." Sets force you to pay for shapes you may never use; individual buying matches your actual workshop. Browse complete burr sets at AIMS for kit options. Maintenance, life and when to retire a burr Carbide is hard but brittle. Three failure modes finish most burrs: Chipping from impact. The most common death mode. Sudden hard contact (edge of a casting, weld crater, deeply pitted surface) chips one or more teeth. The burr keeps cutting on the remaining teeth but unevenly — chatter, rough finish and accelerated wear on the surviving teeth follow. Once chipped, the burr is generally retired for rough-cut work only. Loading and glazing. Aluminium chip-weld is the main cause (see the chip-welding section above). Glazing — where the cutting edges develop a smooth glassy surface — happens on stainless and hardened steel when the burr is run too slow or with too little chip load. Once truly glazed, the burr is finished. Overheating and brazing failure. On burrs where the carbide head is brazed onto a steel shank (most affordable burrs), excessive heat can soften the braze and the head fails off the shank. Solid-sintered carbide burrs (Pferd "Solid Carbide", Sutton VHM) eliminate this failure mode at higher cost. Cleaning the burr. A wire brush (brass for soft metals, steel for ferrous swarf) clears most loading between jobs. For stubborn aluminium clog, the muriatic-acid soak from the chip-welding section above is the workshop fix. Carbide burrs cannot be sharpened in the normal sense — once the teeth are dulled, you replace the burr. (Diamond resharpening services exist for high-value specialty burrs but aren't economic for general workshop burrs.) Common mistakes — what kills burrs and what to do instead Mistake What goes wrong What to do instead Using a burr in a drill chuck Drill too slow (≤3,000 RPM), drill runout damages burr + drill chuck Use a die grinder (10,000+ RPM). If only a drill is available, buy a die grinder before more burrs Running the burr too fast for its head diameter Teeth shed, head shatters, vibration becomes dangerous Check max RPM stamped on burr; follow the RPM-by-diameter chart above Double-cut burr on aluminium without lube Chip welds, burr stops cutting and smears — workpiece ruined Use single cut or NCC; or apply WD-40 / wax to a double-cut Single-cut burr on hardened steel Fewer larger teeth under-engage on hard surface, slow cutting, glazing Use double cut for hard ferrous; reserve single cut for non-ferrous Too much feed pressure Burr grabs and chips, or stalls a cordless die grinder Let the burr's RPM do the cutting; light steady pressure No PPE Carbide chips and metal swarf travel at speed — eye injuries are common Safety glasses minimum, face shield for heavy work, gloves for hot workpieces. See safety glasses and respiratory protection for dust Mismatched shank in collet (1/4" in 6 mm or vice versa) Slip, runout, damaged collet Match shank to collet exactly; check before ordering bulk Buying cheap unbranded burrs for production work Chipping, short life, false economy Trade-tier brands (Pferd, Sutton, Bordo) hold up; budget burrs survive only light hobby use AIMS carbide burr range AIMS stocks 234 carbide burrs at the industrial trade tier — see the full range at /collections/burrs and dedicated kits at /collections/burr-sets. Pferd — 150 SKUs across the full ANSI/DIN range. Includes Pferd's microcut series (the forum-validated reference for fine work), NCC aluminium-cut for non-ferrous production, C3 Plus diamond cut for hardened steel and weld bead, KSK/KUD/WRC and miniature-shank pencil-grinder ranges. German engineering at the workshop standard. Sutton Tools — 34 SKUs, AU manufacturer (Thomastown, VIC). B100/B200/B201/B300 cylindrical square/radius end series, B900 master-cut 5-piece and 10-piece sets, VHM solid-carbide bright finish for premium applications. Bordo — 24 SKUs, AU value tier. Express Cut sets and individual tree/radius/cylindrical shapes for workshop use at trade pricing. Saber — 15 SKUs, including the 8020-S3 1/4" head 3-piece sets and broader range. Klingspor (5 SKUs), P&N (4 SKUs) and Noga (2 SKUs) round out the range. Not stocked at AIMS: Garryson (UK premium), HU-Friedy (US specialty), Total Tools / Sydney Tools / TradeTools branded ranges (Holemaker, Xtorque, Marxman, Renegade Industrial, ATB, Ri), and consumer-tier import kits. AIMS plays the industrial trade tier — call us on (02) 9773 0122 or visit contact us for specialty brand sourcing through our supplier network. Adjacent power-tool guides: Air Tools & Pneumatic Tool Guide covers die grinder selection; Deburring Tool Guide covers hand deburring blades (Shaviv, Noga); Bench Grinder Guide and Angle Grinder Guide cover the bigger abrasive tools. Frequently Asked Questions What is a carbide burr used for? A carbide burr is used to cut, shape, deburr and bevel metal, hard plastics, fibreglass and similar tough materials in a die grinder or rotary tool. Typical applications: weld bead removal, weld bevel prep, engine port work, deburring inside complex shapes, mould and die detail work, fabrication cleanup and metalworking sculpting. The carbide head holds its edge at temperatures and on hardness levels that destroy HSS rotary files. What's the difference between single cut, double cut and diamond cut? Single cut has one helix of teeth — fewer larger teeth, wider chip gullets — best for aluminium, brass, copper and other soft non-ferrous metals (clears chips before they weld). Double cut has two crossing helices — many small teeth — best for steel, stainless and cast iron (smoother finish, faster ferrous removal). Diamond cut is a double-cut burr with extra chip-breaker grooves for aggressive stock removal on hardened steel and weld bead. Microcut has very fine teeth for precision finishing. Can you use a carbide burr in a drill? You can — but you shouldn't. Drills run 1,500–3,000 RPM which is far below the 10,000–25,000 RPM a 1/4" carbide burr needs to cut properly. The burr grabs and tears rather than cuts, the finish is poor, and drill chucks have measurable runout that damages both the burr and the chuck bearings over time. Reddit r/Tools documents drills going "noticeably sloppy" after burr use. Use a die grinder — pneumatic, cordless 18V/12V or electric. What RPM should I run a carbide burr at? RPM depends on head diameter. As a guide: 1/8" head 45,000–90,000 RPM; 1/4" head 25,000–35,000 RPM; 3/8" head 15,000–25,000 RPM; 1/2" head 12,000–22,000 RPM; 5/8"+ 10,000–18,000 RPM. Always check the max RPM stamped on the burr shank. Exceeding the rated RPM risks shedding teeth and shattering the head — at carbide-burr speeds, the outer teeth of a 1/2" burr move supersonic. Forum consensus: "When in doubt, slow down." Why does aluminium clog my carbide burr — and how do I clean it? Aluminium chip-welds itself between the teeth of a double-cut burr because the chips can't clear fast enough. The clog overheats the burr and the workpiece. Three fixes: (1) lubricate with WD-40, paraffin wax or a tea candle while cutting — Practical Machinist standard practice; (2) switch to a single-cut burr with wider chip gullets; (3) use a dedicated NCC (Non-Ferrous Cut) aluminium burr. To clean a clogged burr, chip out what you can with a brass pick then soak the carbide head in muriatic (hydrochloric) acid for 15–30 minutes — the acid dissolves aluminium but doesn't attack the carbide. Wear PPE. What's the difference between a carbide burr and a rotary file? None, in modern usage. "Rotary file" is the older term — burrs were originally described as powered rotary versions of a hand file. ANSI B94.19 calls them "burs" and DIN 8033 calls them "rotary tungsten carbide files." Same physical tool. The "burr" term has won the marketing battle, especially in retail. Can a carbide burr cut hardened steel? Yes — carbide burrs are the standard tool for shaping hardened steel up to around HRC 60. Use a double-cut or diamond-cut burr from a trade-tier brand (Pferd C3 Plus, Sutton VHM, premium Bordo) at the low end of the RPM range with light feed pressure. Cheap import burrs chip on the first hard contact. For tungsten carbide itself or material above HRC 65, you need diamond burrs not carbide. Will a carbide burr cut concrete or masonry? No — carbide burrs are designed for metal, hard plastic and composite cutting, not abrasive material. Concrete, masonry, brick and tile destroy the cutting teeth almost immediately. For masonry use diamond-tipped tools (diamond cup wheels, diamond core bits) — see our angle grinder guide for diamond options. Carbide burrs can be used for very light cleanup on cement/grout but it's not their job. What's the difference between Pferd, Sutton, Bordo and Bunnings burrs? Pferd (German) is the universal forum gold standard at premium tier — the most-quoted burr brand on Reddit. Sutton Tools (Australian, Thomastown VIC) is the AU trade premium equivalent. Bordo (Australian) sits at trade-value tier — solid quality at lower price points. Bunnings-channel brands (P&N, Ozito, Ryobi) play the consumer/light-trade tier — fine for occasional use but not built for production. The price/life economics tip strongly toward Pferd/Sutton for daily use; toward P&N/budget for occasional hobby work. Are diamond-cut carbide burrs better than double-cut? Not better — different. Diamond-cut burrs are double-cut burrs with extra cross-cut grooves that create chip-breakers along each cutting tooth. They remove stock faster on hardened steel and weld bead but leave a rougher finish, and they're worse than standard double-cut on aluminium (more chip-welding). Use diamond cut when you want aggressive removal on tough ferrous material; use standard double-cut for general steel/stainless/cast iron work where finish matters. What size shank do most carbide burrs use — 1/4" or 6 mm? Both are common — and they're not interchangeable. 1/4" = 6.35 mm, 6 mm = 6.00 mm. Industrial die grinders sold in Australia run both collet sizes; you have to check which yours has before ordering burrs in bulk. Trade-tier 1/4" is the US/UK standard and dominates Pferd and Sutton catalogues. 6 mm metric is more common in European-spec pencil grinders and some Trax tools. Mismatched shanks slip, run out of true, damage the collet and shorten burr life. Can I use a Dremel-size (1/8") burr in a die grinder? Only if the die grinder has a 1/8" or 3 mm collet (or a 1/4"-to-1/8" reducer). Most full-size die grinders take 1/4" or 6 mm shanks only — a 1/8" burr won't grip. Pencil-class die grinders (Dotco, Pferd PG, Milwaukee M12 pencil) take 1/8" and 3 mm and are the right host for small-head burrs at the very high RPM they prefer (up to 60,000–90,000 RPM). What is a microcut carbide burr used for? Microcut burrs have many fine teeth — used for precision finishing, mould and die detail work, deburring small parts, intricate engraving and any work where surface finish matters more than removal speed. Pferd's microcut range is the forum-validated reference: Reddit r/Tools, quoted across 10+ threads, calls Pferd 1/8" microcut "mind-blowing compared to dremel brand" for fine work. Slower stock removal but much cleaner finish. How do I know when to retire a carbide burr? Retire a burr when it (a) has visibly chipped teeth that cause chatter and rough cutting, (b) cuts noticeably slower than a new burr of the same shape on the same material, (c) glazes/shines on the cutting edges and stops biting, or (d) the head separates from the shank on brazed burrs. Once retired from primary work, a partly-worn burr can often be relegated to rough-cut prep work on scrap or to soft material. Carbide cannot be sharpened in the normal sense — replacement is the answer. Why does my carbide burr keep chipping? Three common causes. First, impact load — running into edges of castings, weld craters, or hard scale chips teeth. Second, too-fast RPM for the head diameter — at supersonic tooth speeds carbide is brittle and shatters. Third, cheap import quality — Reddit r/Tools "Die grinder carbide Burr chipping" thread documents the quality variance. Solution: use trade-tier brands (Pferd, Sutton, premium Bordo), follow the RPM chart, and approach hard edges with controlled light feed rather than aggressive plunge cuts. For the drive-ratio formula and worked RPM examples, see our Pulley Speed Ratio Calculator guide. People Also Ask — Carbide Burrs Q: What are carbide burrs used for? Carbide burrs (also called die grinder bits or rotary files) are used for grinding, shaping, deburring, and removing material from metal, composites, plastics, and ceramics. Common applications include weld dressing, porting engine components, cleaning up castings, removing burrs from machined edges, and shaping or blending contours that are difficult to reach with conventional tooling. They are used in die grinders, rotary tools, and flexible-shaft machines. Q: What are the different carbide burr cut types and when do I use each? Single-cut burrs have one set of helical flutes and produce a smoother finish with longer chips — suited to ferrous metals. Double-cut (cross-cut) burrs have two overlapping sets of flutes and cut faster with smaller chips, making them more versatile across metals, non-ferrous, and hard materials. Aluminium-cut (upcut) burrs have a coarser, more open flute pattern that prevents the aluminium chips from welding to the burr. Diamond-cut burrs are used on very hard materials including carbide and ceramic. Q: What shank size and speed should I use with carbide burrs? Common shank diameters are 6mm and 3mm, matched to the collet size of the die grinder. Operating speed varies with burr diameter — smaller burrs run faster; larger burrs run slower to maintain an appropriate surface speed. Exceeding the recommended RPM for a given head diameter risks vibration, premature wear, and safety hazards. Consult the tool manufacturer's speed recommendations for the specific burr diameter being used. Q: How do I get the best results and longest life from a carbide burr? Apply consistent, moderate cutting pressure — excessive pressure generates heat and chips the cutting edges; too light a pressure causes rubbing. Move the burr continuously to avoid dwelling in one spot, which creates grooves and localised heat. Ensure the workpiece is securely clamped. For ferrous metals, a light application of cutting oil reduces heat and extends burr life. Keep the grinder at the recommended speed; dropping below speed under load causes rubbing. Inspect burr cutting edges before use for chips or damage. Q: What safety precautions apply when using carbide burrs? Always wear appropriate eye protection — safety glasses are the minimum; a face shield is recommended for overhead work or heavy stock removal. Wear appropriate gloves and ensure loose clothing is clear of the rotating tool. Secure the workpiece — never hold it by hand while grinding. Follow the die grinder manufacturer's maximum RPM and never exceed the burr's rated speed. Flying chips are a hazard to others in the area; consider positioning and barriers when working near colleagues.
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Read moreCobalt Drill Bit Guide: HSS-Co Grades, M35, M42 & When to Upgrade
The single most-asked question in any Australian metal-working workshop: "What drill bit do I use for stainless steel?" The answer, ninety percent of the time, is a cobalt drill bit. Understanding why takes a few minutes — and getting the wrong cobalt drill bit (or the right cobalt drill bit but using it incorrectly) is the difference between drilling 304 stainless cleanly all day and replacing burnt bits every five holes. Cobalt drill bits are not a coating. They are not "cobalt-coloured" because of a finish. The cobalt is alloyed into the high-speed steel itself — typically 5% (M35 grade) or 8% (M42 grade) — which raises the steel's hot hardness and lets the cutting edge survive the heat that ordinary HSS can't handle. That's the whole engineering story, and it's why cobalt is the standard for stainless, hardened steel, cast iron and high-tensile bolts. This guide covers what cobalt drill bits actually are, the grade differences (M35, M42, HSS-PM), the materials they're designed for, the technique that makes them last (and the technique that wastes them in five seconds), brand selection in the Australian market, and the cost reality of when cobalt pays back vs staying with premium HSS or upgrading further to solid carbide. For the broader drill bit selection guide covering all materials and bit types, see our Choosing the Right Drill Bit guide and Types of Drill Bits reference. This article focuses specifically on cobalt as a substrate choice. Need another reference chart? Browse the full AIMS Engineering Reference Charts library — drill bit sizes, tap drill, torque, viscosity, GD&T, AS/NZS standards and more. Cobalt Drill Bit Selector — Choose by Job This guide is a working selector tool — not just a reference. Use it to choose the right cobalt drill for your job. Pick your scenario below for a direct path to the right product, or scroll down for the full M35-vs-M42 grade comparison and material-by-material selection. How to use: 1. Pick your scenario 2. View the product 3. Choose your size from the variant selector Stainless Steel Drilling M35 cobalt — workshop standard Sutton D108 View → Heavy-Duty Production M42 cobalt bulk pack Sutton D109 View → 19-pc Metric Cobalt Set 1mm-10mm in case Sutton D109SM2 View → Imperial Cobalt Sizes 1/16" - 1/2" range Sutton D108 View → Hardened Steel (>30 HRC) Black Magic stub — TiAlN coated Sutton D153 View → Premium Coated Cobalt Black Magic jobber TiAlN Sutton D169 View → Browse Full Cobalt Range All sizes + grades + sets Collection View → Compare to HSS / Carbide Decision guide Selection Guide View → Cobalt drills are the right answer for stainless steel, hardened steel (up to ~50 HRC), titanium, high-tensile bolts, and anything where HSS bright drills work-harden and snap. For mild steel + occasional drilling, regular HSS is more economical (see Drill Bit Selection Guide). Need help? Call (02) 9773 0122. Jump to: M35 vs M42 vs HSS / Carbide Stainless Hardened Steel Speed/Feed/Fluid Identification Brands Cost Analysis Related Selectors AIMS Top Picks — Pick the Right Cobalt Drill Bit Cobalt (HSS-Co, typically M35 or M42) drills bridge the gap between HSS jobber and solid carbide — better than HSS on tough materials (stainless, work-hardened steel), cheaper than carbide, more forgiving on hand-held + manual machines. AIMS stocks Sutton's professional cobalt range plus Bordo value-tier cobalt. Call (02) 9773 0122 for size advice. Workshop Default — Sutton D108 Range Application AIMS recommendation Why this one Workshop default — metric sizes Sutton D108 Cobalt Jobber Metric The AU workshop standard cobalt drill. Colour-tempered for visual identification. 1.0–13.0mm metric range Imperial workshop sizes Sutton D108 Cobalt Jobber Imperial Same D108 in imperial (1/16"–1/2") — for older drawings + US machinery work Heavy duty production (bulk pack) Sutton D109 Heavy Duty Cobalt Bulk Pack D109 = upgraded cobalt content for production volume. Bulk pack pricing for fab shops Left-hand cobalt (stud extraction) Sutton D202 Left-Hand Cobalt Jobber Left-hand cut direction — for broken stud extraction. The cobalt + reverse rotation combo backs out broken bolts as it drills Bordo Value-Tier Cobalt Application AIMS recommendation Why this one Bordo 2011 series (workshop value) Bordo HSS Cobalt Jobber 2011 Series Bordo's professional cobalt range — workshop value tier vs Sutton D108. Mid-price quality Bordo 2010 series Bordo HSS Cobalt Jobber 2010 Series Entry-level Bordo cobalt — for occasional cobalt work where premium tier isn't justified When to Step Up from Cobalt to Carbide Cobalt is the right answer for ~80% of stainless, work-hardened and heat-treated steel work. Step up to solid carbide when you're doing PRODUCTION volume (50+ holes/day in tough material), or when the material is over 40 HRC (hardened tool steel, Inconel, hardened bearing steel). For carbide drilling, AIMS stocks Sutton D300/D304/D306/D310/D323 VHM TiCN/AlCrN range — see the Drill Bit Selection Guide. Buying tip from AIMS: Cobalt drill bits look identical to HSS — the cobalt is alloyed throughout, not coated. Sutton's D108/D109 use a heat-temper colour as a visual identifier. If your drill isn't colour-tempered or marked "HSS-Co" / "M35" / "M42", it's probably HSS, not cobalt. Use cobalt for stainless 304/316 (drills 2-3× longer than HSS) and for any material where HSS work-hardens. For mild steel, HSS jobber (Sutton D101/D102 Bullet) is still the more economical choice.What is a cobalt drill bit? A cobalt drill bit is a high-speed steel (HSS) drill bit with cobalt alloyed into the steel itself. The cobalt is part of the steel — not a surface treatment, not a coating. You cannot scrape the cobalt off; it is the steel. The two main cobalt grades are designated by their cobalt content: M35 grade — 5% cobalt. The standard cobalt drill bit. Significantly better than plain HSS in heat-generating cuts. The default upgrade choice from M2 HSS for stainless steel and most hardened metals. M42 grade — 8% cobalt. The premium cobalt grade. Higher hot hardness still, longer life in stainless and very hard steels. About 30–40% more expensive than M35; chosen for production-volume work or particularly demanding materials. The cobalt addition raises the steel's red hardness — the temperature at which the steel begins to soften and lose its cutting edge. Standard M2 HSS softens around 600°C; M35 cobalt holds its edge to about 650°C; M42 to about 700°C. That additional 50–100°C is the difference between cutting cleanly through stainless steel and burning the cutting edge off in three holes. Visually, cobalt drill bits typically have a duller, more golden or bronze tint than bright HSS — but colour alone is not a reliable indicator. Cheap drill bits sometimes use surface colouring to imply cobalt content that doesn't exist. The only reliable indicator is the manufacturer's marking and the brand reputation behind it. M35 vs M42 vs HSS-PM — cobalt grade selection Grade Cobalt content Red hardness Best for Cost (vs M2 HSS) M2 HSS (baseline) 0% ~600°C Mild steel, aluminium, brass, copper, plastics, timber 1× M35 (5% Co) 5% ~650°C Stainless 304/316, hardened steel to ~30 HRC, cast iron, high-tensile bolts up to grade 8.8 ~1.5–2× M42 (8% Co) 8% ~700°C Heavy stainless production, 17-4 PH, hardened steel to ~45 HRC, high-tensile bolts grade 10.9, abrasive materials ~2.5–3× HSS-PM (Powder Metallurgy HSS, e.g. ASP 2030, T15) 5–10% (varies) ~700°C, plus toughness boost Same materials as M42, plus very interrupted cuts and shock-loaded applications. Premium specialty. ~3–5× Solid carbide (next step up) — ~900°C+ Hardened steel above 45 HRC, titanium, abrasive composites, production CNC ~5–10× M2 HSS The practical selection rule: Drilling stainless 304 or 316 occasionally in a workshop? Use M35. The cost premium over M2 HSS is small; the performance gain is enormous. Production drilling in stainless, repetitive work, or material harder than 304? M42. The extra 30–40% cost is paid back many times over in tool life. Hardened steel above 45 HRC, or any application where M42 still struggles? Solid carbide. Cobalt's red hardness ceiling has been reached. HSS-PM is specialist territory — interrupted cuts in hardened material, shock-loaded applications, high-precision sharpenability. Most workshops never need it. Cobalt vs HSS, cobalt vs carbide — where each fits Three substrates, three different sweet spots. The choice isn't "best material" — it's matching the substrate to the application. Property M2 HSS M35/M42 cobalt Solid carbide Hardness ~63–66 HRC ~67–70 HRC ~89–93 HRA (≈75–80 HRC) Hot hardness ceiling 600°C 650–700°C 900°C+ Toughness (resistance to chipping) High Slightly lower than M2 Brittle — chips easily Resharpenable Yes (basic grinder) Yes (with care) Specialist regrinding only — not economical Cost (10 mm twist drill) ~$8–15 ~$15–35 (M35) or $25–50 (M42) ~$50–120 Best for Mild steel, soft non-ferrous, timber, plastics Stainless, hardened steel, high-tensile bolts, cast iron Above ~45 HRC, titanium, hardened production work Worst for Stainless (work-hardens, burns out) Above ~45 HRC (cobalt softens before cutting) Interrupted cuts (shatters), DIY hand drilling (snaps) The pattern: as you move from M2 HSS → cobalt → carbide, hardness goes up but toughness goes down. Cobalt sits in a sweet middle position — hard enough for stainless and hardened steel up to about 45 HRC, tough enough to survive hand drilling and interrupted cuts that would shatter solid carbide. For most Australian workshop drilling needs above mild steel, cobalt is the right answer. For the analogous decision on end mills, see our Carbide vs HSS End Mill deep-dive — the substrate logic is similar but the application differences (rotational drilling vs side-cutting milling) shift the breakpoints. Stainless steel: the cobalt sweet spot Austenitic stainless steel — 304 and 316, the most common AU industry grades — has one specific behaviour that defeats ordinary HSS drill bits and makes cobalt the right choice: work-hardening under heat and pressure. When a drill bit cuts stainless steel, friction generates heat at the cutting edge. The stainless steel surface beneath the cutting edge responds to this heat by becoming harder — a layer typically 0.05–0.2 mm thick that's measurably harder than the parent material. If the drill bit can't cut through this hardened layer, it rubs instead of cuts; rubbing generates more heat; more heat creates a deeper hardened layer; and the bit either burns its cutting edge off (HSS) or simply skates across a now-hardened surface. Cobalt's higher red hardness lets the cutting edge stay sharp at the temperatures that work-harden stainless. The bit cuts through the work-hardened layer faster than a new layer forms. Combined with correct technique, cobalt drills stainless cleanly. The same cobalt-HSS logic applies up the scale: for larger-diameter structural stainless holes that exceed twist drill capacity (16-50mm+), the cobalt-grade annular cutter in a magnetic drill uses the same red-hardness advantage with the same technique rules — slow RPM relative to mild steel, continuous coolant, solid steady feed, never pause mid-cut. The stainless steel work-hardening warning If you drill stainless steel at high RPM, with light pressure, or with pauses mid-hole, you create a work-hardened zone that even a premium M42 cobalt cannot drill through. The correct technique is the opposite of intuition: slow speed, firm consistent pressure, continuous cutting fluid, no pausing once started. Pecking — lifting the bit and restarting — is the classic failure mode. Once you create the hardened zone, the drill is finished and probably so is the bit. Forum reality: r/metalworking's "Can't for the life of me drill through stainless steel" thread (110+ comments) is almost entirely diagnoses of work-hardening from incorrect technique. The correct stainless steel drilling technique: Slow speed. A 6 mm cobalt bit in 304 stainless wants approximately 200–400 RPM, not 1,000+. A 12 mm bit wants 60–120 RPM. The general rule: about one-third the speed you'd run for mild steel. Firm consistent pressure. Push the bit hard enough that it's continuously cutting (chips coming off, not dust). Light pressure equals rubbing equals work-hardening. Continuous cutting fluid. Even a few drops of thread-cutting oil or dedicated stainless fluid (Trefolex, Tap Magic) makes a substantial difference in bit life and finish quality. Soluble oil also works on benchtop drilling. Don't peck or pause. Once the bit is engaged, keep cutting until the hole is through. Lifting the bit creates a perfect work-hardened ring at the depth you stopped — then the next cut hits hardened material before any fresh cutting can start. Start with a centre punch. Cobalt bits don't like wandering; a centre-punched divot keeps the bit on target from the first revolution. Use a sharp bit, not a tired one. A dull cobalt bit on stainless is just creating heat and hardening the material. Resharpen or replace. For full speeds and feeds reference across all material/bit combinations, see our Cutting Speeds and Feeds Chart. For cutting fluid selection by application, see our Cutting Fluids Guide. Hardened steel: cobalt's outer limit Cobalt drill bits handle hardened steel up to approximately 45 HRC reliably with M42 and 30–35 HRC with M35. Above that, you're approaching the cobalt ceiling and solid carbide is the appropriate next step. Material hardness Recommended substrate Notes Up to ~25 HRC (mild and medium-tensile steel) M2 HSS Cobalt is overkill — premium HSS handles this fine 25–35 HRC (high-tensile bolts grade 8.8, some heat-treated steel) M35 cobalt Standard cobalt territory 35–45 HRC (heat-treated tool steel, hardened spring steel, grade 10.9 bolts) M42 cobalt Slow speed and good fluid mandatory 45–55 HRC (hardened tool steel, dies) Solid carbide (TiAlN coated) Cobalt softens at the cutting temperatures generated; carbide handles it 55+ HRC (case-hardened surfaces, hardened bearings) Solid carbide or specialty (CBN grinding) Drilling becomes very difficult; sometimes annealing is required first The "stuck bolt" scenario. Snapped grade 8.8 bolts, broken taps, hardened studs — the classic AU workshop "I need to drill out something hard" job. Forum consensus from Practical Machinist and Reddit r/Machinists is consistent: M42 cobalt is the standard first attempt; if M42 won't bite, the bolt is harder than 45 HRC and it's solid carbide territory. For broken tap removal specifically, see our Broken Tap Removal Guide. Cast iron, high-tensile bolts and abrasive materials Beyond stainless and hardened steel, cobalt drill bits are the right choice for several other Australian-workshop materials: Cast iron — abrasive but not particularly hard. Cobalt's wear resistance pays off; the chip is short and crumbly which doesn't load the flutes. Drill cast iron dry — adding cutting fluid creates an abrasive paste that wears the bit faster than dry cutting. M35 is usually sufficient. High-tensile bolts (grade 8.8, 10.9, 12.9) — bolt grades 8.8 and above are heat-treated and run 30–45 HRC. Cobalt is the appropriate substrate; M42 for the harder grades. Drill slowly with cutting fluid, don't peck. Spring steel and music wire — heat-treated, 50–55 HRC. M42 cobalt occasionally works at very low speeds; solid carbide is more reliable. Inconel and high-temperature alloys — work-hardens severely, generates high heat. M42 cobalt is workable for one-off holes; production volume = solid carbide with appropriate coatings. Titanium and titanium alloys — low thermal conductivity means heat stays in the bit. M42 cobalt is marginal; solid carbide with AlCrN or similar coating is the standard production choice. Abrasive composites (fibreglass, carbon fibre) — pure abrasive wear regardless of hardness. Solid carbide or PCD-tipped is the long-life choice; cobalt works for small volumes. Speed, feed, and cutting fluid for cobalt Cobalt's hot-hardness advantage only delivers if you give the bit the conditions to use it. Wrong speed and feed make a $30 cobalt drill bit perform like a $5 HSS — burning out fast and leaving a rough hole. Material Cobalt cutting speed (V_c, m/min) RPM for 6 mm bit RPM for 10 mm bit Cutting fluid Stainless 304 15–22 800–1,170 480–700 Trefolex / Tap Magic / sulphurised cutting oil Stainless 316 12–18 640–960 380–570 Same — 316 needs slightly slower Hardened steel 30–40 HRC 10–15 530–800 320–480 Sulphurised oil, slow steady feed Cast iron (grey) 25–35 1,330–1,860 800–1,110 Dry — no fluid Mild steel (cobalt overkill) 30–45 1,600–2,400 950–1,430 Soluble oil or none for short jobs Aluminium (cobalt overkill but works) 60–100 3,180–5,300 1,910–3,180 WD-40 or kerosene The general rule for cobalt vs HSS speeds: cobalt runs at the same speed as HSS in mild steel, about 1.5× HSS speed in stainless (because HSS shouldn't really be used in stainless), and well below HSS speed in hardened material. Slower than you might think — many DIY drilling failures come from running cobalt at the same speed you'd use for mild steel HSS. Feed rate matters as much as speed. Light feed (low pressure on a hand drill, low feed setting on a drill press) creates rubbing rather than cutting and burns the bit. A cobalt drill bit wants firm, consistent feed pressure that produces continuous chips — a chip should be coming out of the hole every revolution. Hand drill vs drill press technique Cobalt drill bits work in both, but the technique differs. On a drill press: set the speed correctly for the material and bit diameter; clamp the work; apply firm continuous feed; use cutting fluid liberally. Drill press technique is mostly about the setup — once the speed and clamping are right, the cutting itself is straightforward. In a hand drill (battery or corded): the challenge is the operator. You need to maintain consistent feed pressure, hold the drill straight (no wobbling), and stop cleanly through the back side of the work. Hand-drilling stainless with cobalt is achievable but requires: The drill set to low speed — most cordless drills have a Hi/Lo selector. Use Lo. If yours has variable trigger, run it at maybe 30–40% trigger pull. A centre punch on the marked spot before starting (cobalt bits hate wandering) Both hands on the drill, body weight behind it, feeding firmly A squirt of cutting fluid applied before starting and re-applied if you stop No stopping mid-hole. If you must stop, lift the bit clear and re-apply fluid before continuing. Watch the chip colour. Bright silver chips = correct technique. Blue or brown chips = too much heat — slow down or apply more fluid. Hand-drilling thicker stainless (above 6 mm) with a small cobalt bit is hard work. For repetitive work in stainless, a drill press or magnetic base drill makes the job dramatically easier. Cobalt drill bit identification — markings and what to look for How to tell whether a drill bit is genuinely cobalt — and what grade: Manufacturer marking. Premium cobalt drill bits are laser-marked or stamped with the grade designation (M35, M42, HSS-Co5, HSS-Co8). Sutton, Bordo, Tivoly, Dormer, Cleveland, Triumph and other premium brands all mark their cobalt clearly. Unmarked or vaguely-marked drill bits should be assumed to be standard HSS regardless of seller claims. Standards markings. Cobalt drill bits to DIN 338 = jobber-length cobalt twist drill DIN 1869 or DIN 340 = long series cobalt DIN 1897 = stub series cobalt The DIN number is followed by the grade: HSS-Co5, HSS-Co8 Colour is unreliable. Genuine cobalt is typically a duller gold/bronze tint than bright HSS, but cheap drill bits can be artificially coloured to look the same. Don't rely on colour alone. Magnetism. Cobalt drill bits remain magnetic (it's still steel, just alloyed). Solid carbide drill bits are barely magnetic — if a "carbide" drill bit sticks to a magnet strongly, it's likely not solid carbide. Brand reputation. A Sutton-marked, Tivoly-marked or Dormer-marked cobalt drill bit is genuine cobalt at the stated grade. An unbranded or generic-branded "cobalt" drill bit on eBay or marketplace at one-third the price of premium is a quality risk regardless of marketing claims. The Practical Machinist thread "Where can you get a REAL M42 cobalt drill?" exists because so much "M42" tooling on the cheap end of the market is mis-marked. Brand selection in the Australian market Sutton Tools (manufactured in Thomastown, Victoria) — Australia's premium cobalt drill bit manufacturer. Comprehensive M35 and M42 ranges across jobber, stub and long-series formats. The standard recommendation for most Australian workshops. AIMS stocks the Sutton range — see the Sutton Tools collection. Bordo — Australian-distributed range, strong on M35 cobalt and HSS. Good value for hand-drill use and moderate workshop volumes. AIMS-stocked. Tivoly (France) — premium European cobalt manufacturer, available in AU through specialist tool distributors. Excellent quality, premium price. Dormer (UK/Sweden, now Dormer Pramet) — premium European brand with full cobalt range. Available through industrial distributors. Other premium brands available in AU on order: Cleveland (USA), Triumph (USA), OSG (Japan), Mitsubishi (Japan), YG-1 (South Korea — value premium). Avoid: unbranded cobalt drill bits on eBay, marketplace listings, or budget retailers at unrealistic prices. Forum-validated reality: cheap "M42 cobalt" sets often turn out to be standard HSS coloured to look like cobalt, or M35 sold as M42, or cobalt content well below the marked grade. A premium HSS bit ($10) typically outperforms a $5 fake-cobalt every time. Cheap "cobalt" quality variance warning Budget drill bit sets marketed as "cobalt" or "M42" frequently fail testing — wrong cobalt content, wrong grain structure, or no cobalt at all. The Practical Machinist thread "Where can you get a REAL M42 cobalt drill?" runs to many pages of disappointed buyers. If a cobalt drill bit set costs less than premium HSS, scepticism is warranted. Stick to brands you can verify: Sutton, Bordo, Tivoly, Dormer, Cleveland, Triumph, OSG, Mitsubishi, YG-1. Cost reality: when does cobalt pay back vs premium HSS? The premium for genuine cobalt over premium HSS is real but smaller than people assume: Bit (10 mm jobber, premium AU brands) Approx AU price (single bit) Multiplier M2 HSS (premium, e.g. Sutton/Bordo) ~$8–15 1× M2 HSS with TiN coating (gold) ~$12–20 ~1.3× M35 cobalt (5%, e.g. Sutton M35) ~$15–25 ~1.5–2× M42 cobalt (8%, premium) ~$25–45 ~2.5–3× HSS-PM specialty (e.g. ASP 2030) ~$40–80 ~4–5× Solid carbide (TiAlN-coated) ~$50–120 ~5–8× The payback math: A premium HSS bit drilling stainless will drill maybe 5–10 holes before the cutting edge is gone, then needs resharpening or replacement. A premium M35 cobalt in the same stainless will drill 50–100 holes before resharpening is needed. The cobalt's life is roughly 10× longer in stainless. At 1.5–2× the bit cost, cobalt pays back the upgrade cost on the second hole and everything after that is pure savings. In materials where HSS works fine (mild steel, aluminium, brass, timber), cobalt is overkill — you're paying 1.5–2× for performance you don't need. Run HSS for the easy materials and keep cobalt for stainless, hardened steel, and the genuinely hard materials. Build a mixed kit: the right Australian workshop drill bit kit is a mix — premium HSS in common sizes for general work, plus M35 cobalt in 4–10 mm sizes for stainless and hardened material work. Add M42 for production-volume stainless. Solid carbide for jobs where cobalt has reached its limit. Common mistakes that kill cobalt drill bits early Cobalt drill bits should last a long time. When they fail prematurely, it's almost always one of these mistakes: Running too fast. The most common error. Cobalt's heat-resistance advantage doesn't help if you generate so much heat that even cobalt's ceiling is exceeded. In stainless, slower than your instinct says. Pecking — lifting and restarting. Each lift creates a work-hardened ring; the next cut hits the hard ring and burns out the cutting edge. Once you start, finish. No cutting fluid. Stainless and hardened steel need fluid. A few drops of thread-cutting oil makes the difference between a bit that lasts and a bit that burns out. Light feed pressure. Rubbing instead of cutting work-hardens the material and overheats the bit. Push firmly enough to be cutting continuously. Using cobalt where HSS would do. Not a failure, just waste — you're consuming expensive bits on jobs that don't need them. Using HSS or "cobalt"-marked-cheap-bit on stainless. Burns out, gets blamed on the work, gets replaced with another cheap bit, repeats. The real fix is genuine cobalt. Drilling cast iron with cutting fluid. Counter-intuitive but true — fluid + iron dust creates abrasive paste. Drill cast iron dry. Not centre-punching. Cobalt bits wander if not started in a punch mark. Wandered bits make oversized, off-centre holes and stress the cutting edge. Letting the bit stop in the hole. Battery dying mid-cut, drill press tripping, hand drill clutch slipping — all create the work-hardening trap. Buying unverified cheap "cobalt" bits. If it's not genuine, the cobalt benefit isn't there regardless of the marking. Cobalt drill bits at AIMS Industrial AIMS stocks Sutton M35 and M42 cobalt drill bits (Australian-made), Bordo M35 cobalt, and selected premium imports. Browse the full range in our dedicated Cobalt Drill Bits collection. For other drill bit types and the broader cutting tool range: Jobber Drill Bits collection — HSS jobber-length twist drills for general metal and timber work Sutton Tools collection — full Sutton range including HSS, cobalt and solid carbide drill bits, taps, reamers and end mills Carbide Drill Bits collection — for the next-step upgrade above cobalt's limit (hardened steel above 45 HRC, titanium, abrasive composites) For specific cobalt grades, sizes, or premium imports we don't show online, call us on (02) 9773 0122 or use our contact page. We can source most premium cobalt and carbide drill bits available in the Australian market. For the broader drill bit selection guide covering all materials, see our Choosing the Right Drill Bit Guide and Types of Drill Bits reference. When a fastener won't come loose with normal effort, walk through the full escalation in our How to Remove Stuck Bolts & Nuts guide — penetrant through to drill-out and weld-on. Related AIMS Selectors This guide complements AIMS's other drilling selectors. Use them together for complete coverage: Drill Bit Size Selector — every metric drill diameter linked to AIMS-stocked SKU. Drill Bit Selection Guide — broad guide on HSS vs cobalt vs carbide for general drilling. Tap Drill Size Selector — for threading work, gives you the tap + matching drill SKU. Tap & Die Selection Guide — companion guide on tap selection (also cobalt for stainless). HSS vs Carbide End Mill — when carbide is worth the cost (same material principle as drills). Cutting Speeds & Feeds Reference — RPM and feed rate for cobalt drilling by material. Cutting Tool Materials — HSS, cobalt, carbide grades compared. Cutting Tool Coatings — TiN, TiAlN, AlCrN, when each matters for cobalt drills. Cutting Tool Troubleshooting — walking drills, oversize holes, snapped tips. Or browse the full cobalt drill bits range + jobber drill bits + reduced shank for larger sizes — Sutton primary, Bordo and P&N alternates, in stock for next-day Australia-wide dispatch from our Milperra warehouse.Frequently Asked Questions What is the difference between HSS and cobalt drill bits? Cobalt drill bits are high-speed steel with cobalt alloyed into the steel itself — typically 5% (M35) or 8% (M42). The cobalt isn't a coating; it's part of the steel. The cobalt addition raises the steel's red hardness (the temperature at which the cutting edge begins to soften) from about 600°C for plain M2 HSS to 650–700°C for cobalt grades. This extra heat resistance makes cobalt the right choice for stainless steel, hardened steel, cast iron and high-tensile bolts where ordinary HSS burns the cutting edge off in a few holes. Are cobalt drill bits worth the extra cost? For drilling stainless steel, hardened steel, cast iron, or high-tensile bolts — yes, by a wide margin. A cobalt drill bit in stainless typically lasts 5–10× longer than HSS at 1.5–2× the price, paying back the upgrade cost on the second hole. For drilling mild steel, aluminium, brass, or timber where HSS works fine, cobalt is overkill — premium HSS is a smarter spend. Build a mixed kit: HSS for general work, cobalt M35 for stainless and hardened material, M42 for production-volume hard work, solid carbide for above 45 HRC. What is the difference between M35 and M42 cobalt drill bits? M35 contains 5% cobalt; M42 contains 8% cobalt. The higher cobalt content gives M42 a slightly higher red hardness (~700°C vs ~650°C for M35), longer tool life in stainless and hardened steel, but at 30–40% higher price. For occasional stainless drilling, M35 is sufficient and cost-effective. For production-volume stainless work or hardened steel above 35 HRC, M42 pays back the cost premium through longer tool life. Above 45 HRC, both are at their limit and solid carbide is the right next step. What is the best drill bit for stainless steel? A genuine M35 or M42 cobalt jobber drill bit from a verified premium brand (Sutton, Bordo, Tivoly, Dormer), used with correct technique: slow speed (about one-third of mild steel speed), firm consistent feed pressure, continuous cutting fluid, and no pausing once started. The combination of cobalt substrate plus correct technique handles 304 and 316 stainless cleanly. Cheap "cobalt" drill bits on eBay or budget retailers frequently fail because the cobalt content is below the marked grade or absent entirely. Why does my drill bit keep burning out in stainless steel? Almost always one of: running too fast (stainless wants slow speed — about one-third of mild steel RPM); pecking (lifting and restarting creates a work-hardened zone); insufficient cutting fluid (stainless needs continuous fluid); light feed pressure (rubbing instead of cutting work-hardens the material); or using HSS instead of cobalt. The mechanism is stainless steel's work-hardening behaviour — under heat and friction the surface gets harder, and if your bit can't cut through the hardened layer faster than new layers form, it rubs and burns. Fix: cobalt M35 or M42, slow speed, firm feed, continuous fluid, no pausing. Is M42 cobalt better than carbide for hardened steel? Up to about 45 HRC: M42 cobalt is the right choice. Cobalt is much tougher than carbide and survives the interrupted cuts and slight misalignment that hand drilling creates. Above 45 HRC: solid carbide takes over because cobalt softens at the cutting temperatures generated. The crossover point depends on how hard the material is and how production-grade your setup is — for occasional hand-drill work, M42 cobalt can stretch up to 50 HRC if you go slow with fluid; for production work, carbide above 45 HRC. Can cobalt drill bits be resharpened? Yes — cobalt is just alloyed HSS, so it sharpens on the same equipment as standard HSS drill bits. A drill bit sharpener (Drill Doctor, Tradesman) handles cobalt fine; a bench grinder with the right wheel and a steady hand also works. The cutting edge geometry matters: 135° split-point is the modern standard for stainless and metal drilling, much better than the older 118° tip. Cobalt holds a sharp edge well after regrinding. The regrindability is part of the cost story — a $25 cobalt bit with two regrinds at $5 each delivers $35 total cutting capacity. Are cobalt drill bits the same as cobalt-coated drill bits? No — and the distinction matters. Genuine cobalt drill bits have cobalt alloyed into the steel itself (5% for M35, 8% for M42). The cobalt is part of the steel and stays there even after resharpening. "Cobalt-coated" or "cobalt-finish" drill bits are HSS with a thin surface treatment — the coating wears off in normal use and is gone after the first regrind. Marketing language sometimes blurs this distinction; check for the M35 or M42 grade marking, and the brand reputation, to verify genuine cobalt. What cutting fluid should I use for drilling stainless with cobalt? For stainless steel: a sulphurised cutting oil is the standard recommendation — Trefolex, Tap Magic, Rocol RTD, or similar dedicated thread-cutting and stainless drilling fluids. Even general-purpose soluble oil or a few drops of motor oil is better than nothing. For hardened steel: same — sulphurised oil. For cast iron: nothing — drill dry, fluid creates abrasive paste. For mild steel: optional, but soluble oil extends tool life. For aluminium: WD-40 or kerosene work well; never sulphurised oil (stains aluminium). See our Cutting Fluids Guide for the full breakdown. Why are some cobalt drill bits gold-coloured and others silver? The colour difference is mostly cosmetic. Bright silver/grey is uncoated genuine cobalt — the natural colour of HSS-Co. Gold-tinted cobalt bits have a thin TiN (titanium nitride) coating over the cobalt substrate, intended to add slightly more wear resistance. The TiN coating wears off the cutting edge in normal use, after which the bit performs identically to uncoated cobalt. The colour is not a reliable indicator of cobalt grade — check the manufacturer's marking (M35, M42) for the actual grade. Cheap drill bits sometimes use gold colouring to imply cobalt content that doesn't exist. Can cobalt drill bits drill through hardened bolts? Yes — that's exactly what they're designed for. Grade 8.8 high-tensile bolts run about 30 HRC; grade 10.9 about 35 HRC; grade 12.9 about 40 HRC. M35 cobalt handles 8.8 cleanly; M42 cobalt handles up to 10.9 reliably and 12.9 with care. Above grade 12.9, you're approaching solid carbide territory. Technique matters: slow speed, cutting fluid, firm feed, no pecking. For broken bolt extraction specifically (snapped studs in tapped holes), see our broken tap removal guide — same principles apply for studs. What is HSS-PM and is it worth the extra cost over M42? HSS-PM stands for high-speed steel — powder metallurgy. The steel is produced from atomised powder rather than conventional ingot casting, giving a more uniform grain structure and higher toughness at the same hardness. Common designations include ASP 2030, T15, M48-PM. HSS-PM holds an edge as well as M42 cobalt with better toughness, particularly in interrupted cuts and shock-loaded applications. The cost premium is significant — typically 3–5× M2 HSS — and most workshops will never need it. Specialist territory for production-volume hard milling and drilling. How fast should I run a cobalt drill bit? Significantly slower than you'd run HSS in mild steel. For 304 stainless with a 6 mm cobalt bit: 800–1,170 RPM. For 10 mm: 480–700 RPM. For 12 mm in 316 stainless: 320–480 RPM. For hardened steel: lower again — about half those numbers. The general rule for cobalt: about one-third the speed of mild steel for stainless, half the speed for hardened material, and same speed as HSS for mild steel and aluminium. See our Cutting Speeds and Feeds Chart for the full reference table. Are budget cobalt drill bit sets worth buying? Generally no. The Practical Machinist thread "Where can you get a REAL M42 cobalt drill?" runs to many pages of buyers reporting that budget cobalt sets test out as standard HSS or low-cobalt M35 sold as M42. The cost saving is real (~30–50% off premium prices) but tool life is often half or less of premium cobalt — wiping out the saving on the first major job. A premium M35 from Sutton, Bordo, Tivoly or Dormer at $15–25 is a smarter spend than a $40 unbranded "M42" set with 13 sizes that may or may not actually be cobalt. Quality variance in cheap drill bit sets is huge; brand reputation is the only reliable check. What is a "split point" cobalt drill bit and why does it matter? A split-point drill bit has a small secondary cutting edge ground into the chisel point at the tip — converting the chisel from a wedge that pushes material aside into a cutting edge that cuts material away. The split point is sharper, starts cleanly without wandering, and reduces feed pressure required. For stainless steel and hardened material drilling, 135° split-point geometry is the standard recommendation — it cuts cleanly with less heat generation than the older 118° tip. Most premium cobalt drill bits come split-point as standard. If you're choosing between split-point and standard 118° cobalt for stainless work, choose split-point. For complete metric bolt sizing (M3-M24) with thread pitch and head dimensions, see our Metric Bolt Size Guide. Need sutton tools? Browse the AIMS range at sutton tools.
Read moreHole Saw Guide: Sizes, Arbors & Pilot Drills
Hole Saw Selector — Choose by Trade This guide is a working selector tool — not just a reference. Most hole saw buying decisions come down to "what trade am I doing?" Pick your scenario below for a direct path to the right kit, or scroll down for the full bi-metal vs TCT vs diamond comparison and material-by-material RPM guidance. How to use: 1. Pick your trade / material 2. View the kit 3. Most kits include arbor + pilot drill — check the listing for what's included Electrician (Master Kit) Bi-metal HSS, 14pc 16-64mm Bordo 7010-S1 View → Steel (XP TCT) Tungsten carbide tip, 8pc 16-40mm Bordo 7080-S1 View → Thin Sheet Metal Thinwall design, 8pc kit Bordo 7040-S1 View → Tile / Glass (Diamond) Brilliant Diamond set Bordo 7084-S2 View → Tradesman All-Purpose 11pc 16-60mm general kit Bordo 7030-S1 View → Plumber (Pipe / Deep Cut) Ripper TCT, 16pc 16-114mm Bordo 7075-S3 View → Diamond Holesaw (Sutton) Sutton 8pc segmented set Sutton H1150011 View → Arbors + Pilot Drills Sutton H122 quick-release Sutton H122 View → Bordo XP is the workshop-standard hole saw range at AIMS — premium HSS bi-metal teeth, tungsten carbide tip (TCT) and diamond options. Sutton range covers single hole saws + arbors + pilot drills. P&N for budget kits. Need help? Call (02) 9773 0122. Jump to: Types RPM Sizes By Material Arbors Technique Failures Brands Related Selectors AIMS Top Picks — Pick the Right Hole Saw Fast AIMS stocks 130+ hole saws across bi-metal, TCT carbide, diamond and annular cutters. Sutton + Bordo dominate the AU professional range, with trade-specific sets for sparkies, plumbers, locksmiths and chippies. Recommendations below by material + job. Call (02) 9773 0122 for the right diameter + arbor. For Steel, Sheet Metal & General Workshop Job Type AIMS recommendation Why this one Workshop default (mild steel + sheet) Bi-Metal Cobalt M42 Sutton H125 Bi-Metal Cobalt The AU workshop standard. M42 cobalt teeth on flexible backing — for mild steel up to 5mm + sheet metal Sutton starter kit (5-piece) M42 set Sutton H125BM1 Bi-Metal M42 Starter 5pc 5-piece starter pack — common workshop sizes (19/22/29/35/44mm typical) with mandrel Plumber set (5 pieces) M42 plumber set Sutton H125BM7 M42 Plumber Set Sizes for common AU plumbing pipes — copper, PEX, PVC Heavy duty bi-metal range M42 14–152mm Sutton H105 Bi-Metal Heavy Duty 14–152mm Heavy-duty wall thickness for deeper cuts. Range 14–152mm covers most workshop needs Bordo value bi-metal HSS Cobalt Bi-Metal Bordo HSS Cobalt Bi-Metal Bordo's value-tier bi-metal — workshop volume at lower cost than Sutton premium Engineers set (Pferd 13-piece) Bi-Metal engineers Pferd Bi-Metal Engineers 13pc 13-piece engineering set — covers fab shop standard sizes with mandrel + ejector For Impact Drivers (Tough Materials, Cordless Drills) Job Type AIMS recommendation Why this one Impact-rated bi-metal HSS Impact Sutton H119 Impact Bi-Metal HSS Impact-rated teeth — for use on cordless impact drivers (where standard bi-metal teeth fracture) Impact arbor Impact-rated arbor Sutton H112 Impact Arbor Heavy-duty arbor rated for impact driver torque. Pairs with H119 for impact-driver work Quick release pilot drill (impact) Quick release Sutton H122 Quick Release Pilot Drill One-handed pilot drill change — speeds up trade work, especially in roof/wall cavities For Hardened Steel, Cast Iron & Heavy Duty (TCT Carbide) Job Type AIMS recommendation Why this one Carbide tipped workhorse TCT (Tungsten Carbide Tip) Sutton H128 Carbide Tipped TCT teeth for hardened steel + cast iron + stainless production. 5-10× life of bi-metal on tough material Bordo XP premium TCT TCT XP series Bordo XP TCT Tungsten Carbide Bordo XP — premium TCT range. AU trade favourite for steel beam + thick plate work Bordo XP2 deep cut XP2 deep cut TCT Bordo XP2 Deep Cut TCT Deep-cut variant — for thicker stock (up to 50mm deep). 2025/26 release Bordo Ripper TCT Ripper TCT Bordo Ripper TCT Ripper geometry — aggressive teeth for fast cutting at the expense of finish. Industrial production TCT starter kit (16-40mm) Bordo XP set Bordo XP 8-piece Set 16-40mm 8-piece starter — common steel-cutting sizes in a Bordo XP kit Sutton multi-purpose TCT Multi-purpose TCT Sutton H127 Multi-Purpose TCT Versatile TCT — handles steel, wood, plastic, plasterboard in one disc. For mixed trade work Trade-Specific Sets (Sparkies, Plumbers, Chippies) Trade Set AIMS recommendation Why this one Sparkies (electrical) Bordo 7010-S4 Bordo 7010-S4 Sparky's Kit 16-50mm 9-piece bi-metal set — sizes for common AU GPOs, downlights, conduit, junction boxes Sparkies (master TCT) Bordo 7010-S1 Bordo 7010-S1 Electrician's Master 14pc 14-piece master kit — bi-metal sizes covering full sparky range to 64mm Multi-purpose TCT sparkies Sutton H127MP9 Sutton H127MP9 Multi-Purpose Electrician 6pc TCT for sparkies cutting through mixed materials (plaster + steel stud) Plumbers (pipe + tank) Bordo 7010-S3 Bordo 7010-S3 Plumber's Pipe 16pc 16-114mm 16-piece kit — sizes for AU copper + PVC + PEX pipe and tank flange holes. 114mm max Plumbers TCT (Ripper) Bordo 7075-S3 Bordo 7075-S3 Ripper TCT Plumber's 16pc TCT version of plumber's kit — for cast iron + thick steel pipe Multi-purpose TCT plumbers Sutton H127MP7 Sutton H127MP7 Multi-Purpose Plumber 9pc TCT for plumbers cutting through mixed materials Chippies (carpenter) Sutton H127MP6 Sutton H127MP6 Multi-Purpose Carpenter 8pc TCT for chippies — wood + occasional steel + plaster. 8 common sizes Chippy's master kit (Bordo) Bordo 7010-S2 Bordo Chippy's Master Kit 15pc 15-piece master kit for chippies — covers 16-114mm range Locksmiths Bordo 7010-S5 Bordo 7010-S5 Locksmith's Kit 13pc 10-54mm Locksmith-specific sizes — for door lock + deadbolt installs Downlight installer Sutton H127MP4 Sutton H127MP4 Multi-Purpose Downlight 6pc Downlight-specific TCT sizes — through plaster + steel stud + insulation For Tile, Stone & Concrete (Diamond) Job Type AIMS recommendation Why this one Diamond segmented (concrete + masonry) Diamond segmented Sutton H115 Diamond Segmented 19-105mm Segmented rim for concrete, masonry, brick. 19-105mm range. Pair with H115 pilot drill Bordo diamond (premium tile + porcelain) Brilliant Diamond Bordo Brilliant Diamond Bordo premium diamond — for porcelain tile, marble, granite. Wet cutting recommended Saber diamond hole saw Diamond Saber Diamond Holesaw Saber diamond — value tier diamond for occasional tile work Diamond set (8-piece) Sutton diamond kit Sutton H1150011 Diamond 8pc Kit 8-piece diamond segmented kit — common tile sizes For Annular Cutters (Magnetic Drill Press) Job Type AIMS recommendation Why this one Mag drill annular cutter (HSS) HSS annular Sutton H180 Annular Cutter HSS Standard HSS annular cutter for magnetic base drill machines (mag drills) Mag drill annular cutter (TiAlN coated) HSS TiAlN annular Sutton H182 M2Al HSS TiAlN TiAlN-coated for steel beam + structural drilling on mag drill Euroboor annular cutter Weldon HSS Euroboor 30mm Weldon HSS Euroboor brand — workshop favourite for mag drill operators. Weldon shank standard Buying tip from AIMS: Match the hole saw teeth to the material. Bi-metal cobalt (M42) = workshop default for mild steel up to 5mm + sheet. TCT carbide = step up for hardened steel, cast iron, stainless production, or anything >5mm thick. Diamond = tile, concrete, masonry only (don't use on metal). For impact drivers, use impact-rated bi-metal (Sutton H119) — standard bi-metal teeth fracture under impact load. Always lubricate steel cutting with cutting fluid for 3-5× longer disc life — see the Tap Magic Cutting Fluids Guide.Hole Saw Types — Bi-Metal, TCT, Diamond, Masonry — Quick Reference Four core types cover the full range of materials a hole saw realistically cuts. Bi-metal HSS hole saws (the workshop default) Bi-metal hole saws have a body of low-carbon spring steel with high-speed steel (HSS) teeth electron-beam-welded to the cutting edge. Material Right hole saw Tool / cooling Wood, plasterboard Bi-metal HSS Standard rotary drill, dry Mild steel up to 6 mm Bi-metal HSS Cutting fluid, slow speed Stainless steel TCT Cutting fluid, very slow speed Cast iron, hardened steel TCT Cutting fluid, very slow speed Fibre cement (Hardiplank) TCT (multi-purpose) Standard drill, dust mask, dry Aluminium, brass, copper Bi-metal HSS Cutting fluid optional, moderate speed Tile, porcelain, glass Diamond grit Water cooling mandatory, slow speed Brick, concrete, blockwork Masonry tungsten carbide Hammer drill, dry What a Hole Saw Actually Is — Technical Definition A hole saw is a cylindrical drilling tool that cuts a circular hole by sawing the perimeter rather than removing all the material in the hole. The cup-shaped saw has cutting teeth around its open mouth and a centre pilot drill that locates the cut. As the tool spins, the teeth saw a circular kerf around the circumference; the material inside the kerf — the "core" or "slug" — comes out intact when the cut breaks through. The cut diameter equals the hole saw's outside diameter, less the kerf thickness (typically 1.5–2 mm). Compared to a twist drill bit cutting the same diameter: Far less material removed — only the kerf is cut, not the entire hole volume. A 75 mm hole saw removes about 5% of the material a 75 mm twist drill would. Lower power required — sawing a thin kerf needs a fraction of the torque that drilling the full diameter would. Larger diameters practical — 50–200 mm holes that would be impractical with twist drills are routine with hole saws. For the comparison across all drill bit types and applications, see our Drill Bit Types Guide. Limited depth — cut depth is limited to the cup's internal length (typically 38–50 mm). Deeper holes need step-cutting or annular cutters. Hole saws span four main types defined by the cutting tooth material — bi-metal HSS, tungsten carbide-tipped (TCT), diamond grit, and tungsten masonry. Each type has a defined material range, cutting speed envelope, and service life. Mismatching the hole saw type to the material is the most common cause of premature tooth wear and the second most common cause of "the hole saw didn't work" complaints (the first being wrong RPM, covered later). This guide is written for trade and industrial users — electricians, plumbers, fabricators, sheet-metal workers, and maintenance technicians cutting holes in metal, plastic, wood, and masonry as part of their daily work. The principles apply equally to DIY use; the brand and grade recommendations skew toward professional-grade tools that survive repeated use. Hole Saw Types — Bi-Metal, TCT, Diamond, Masonry Four core types cover the full range of materials a hole saw realistically cuts. Bi-metal HSS hole saws (the workshop default) Bi-metal hole saws have a body of low-carbon spring steel with high-speed steel (HSS) teeth electron-beam-welded to the cutting edge. Cobalt content (typically 8% in M42 grade HSS) increases hardness and heat resistance. Properties: Cuts: wood, plasterboard, plastic, mild steel up to ~6 mm, stainless steel (with reduced speed), aluminium, copper, brass Doesn't cut: hardened steel, cast iron above 200 HB, masonry, tile, glass, ceramic Service life: hundreds of holes in mild steel; thousands in plasterboard or wood Cost: mid-range — typical 60 mm bi-metal $30–60 trade price Bi-metal is the AU workshop default. The Sutton H125 series (cobalt bi-metal) stocked at AIMS is a representative professional-grade range covering 14–127 mm diameters. Tungsten carbide-tipped (TCT) hole saws TCT hole saws have hardened tungsten carbide cutting edges brazed onto the saw body. The carbide is significantly harder than HSS and survives in materials that would dull bi-metal teeth quickly. Properties: Cuts: stainless steel (any grade), hardened steel, cast iron, fibre cement (Hardiplank, Villaboard), abrasive composites, multi-purpose use across mixed materials Doesn't cut: wood at high speed (TCT teeth are brittle and chip on impact), masonry (different carbide grade and tip geometry needed) Service life: 3–5× bi-metal in stainless steel and abrasive materials Cost: 2–3× bi-metal price for the same diameter TCT is specified when bi-metal won't cut the material (stainless, hard steel, fibre cement) or when the application is high-volume production cutting where the longer life pays back the higher cost. Diamond grit hole saws Diamond hole saws have a steel body with industrial diamond grit bonded to the cutting edge — no individual teeth. The diamonds abrade the material rather than sawing it. Properties: Cuts: ceramic tile, porcelain, glass, stone, marble, fibreglass, ceramic-composite materials Doesn't cut: metal (diamonds graphitise on iron at cutting temperature), wood (cutting action is wrong) Critical requirement: water cooling. Diamond hole saws must be flooded with water during cutting to prevent diamond loss and substrate cracking. Dry cutting destroys the saw in minutes. Service life: 30–80 holes in tile depending on tile hardness Cost: mid-to-high; small diamond hole saws are inexpensive but wear fast Tungsten carbide masonry hole saws Distinct from TCT metal hole saws — masonry hole saws use a different tungsten carbide grade (toughness optimised over hardness) and a hammer-action cutting geometry. Properties: Cuts: brick, concrete, mortar, blockwork, cement render Doesn't cut: reinforcing steel within the masonry — hits rebar and stops; need a metal hole saw to clear it Drilling mode: hammer drill or rotary hammer required; standard rotary drill not enough Cost: mid-range; comparable to TCT Material Right hole saw Tool / cooling Wood, plasterboard Bi-metal HSS Standard rotary drill, dry Mild steel up to 6 mm Bi-metal HSS Cutting fluid, slow speed Stainless steel TCT Cutting fluid, very slow speed Cast iron, hardened steel TCT Cutting fluid, very slow speed Fibre cement (Hardiplank) TCT (multi-purpose) Standard drill, dust mask, dry Aluminium, brass, copper Bi-metal HSS Cutting fluid optional, moderate speed Tile, porcelain, glass Diamond grit Water cooling mandatory, slow speed Brick, concrete, blockwork Masonry tungsten carbide Hammer drill, dry Cutting Speed (RPM) — The Most-Missed Specification Hole saw RPM is the single biggest factor in cut quality, tooth life, and successful completion. Wrong RPM kills hole saws. Cuts come from each tooth taking a controlled bite of material — too fast and the teeth skate on heated chips; too slow and the teeth grind without cutting. The relationship between hole saw diameter and target RPM is inverse: larger diameter = slower RPM. Why RPM matters Hole saws are specified by surface cutting speed (SFM in imperial, m/min in metric) — the speed of the cutting edge measured at the tooth tip. Bi-metal hole saws cut mild steel at approximately 25 m/min surface speed. A 25 mm bi-metal cutting at 25 m/min calculates to 318 RPM; a 100 mm bi-metal at the same surface speed calculates to 80 RPM. Same surface speed, very different drill RPM. For the broader cutting speed reference covering drill bits, taps, and lathe operations across HSS, cobalt and carbide tools, see our Drill Speed Chart and Cutting Speeds Reference. Hole saw diameter Mild steel (bi-metal) Stainless steel (TCT) Wood (bi-metal) 20 mm ~400 RPM ~150 RPM ~1500 RPM 30 mm ~270 RPM ~100 RPM ~1000 RPM 50 mm ~160 RPM ~60 RPM ~600 RPM 75 mm ~110 RPM ~40 RPM ~400 RPM 100 mm ~80 RPM ~30 RPM ~300 RPM 150 mm ~50 RPM ~20 RPM ~200 RPM These are starting figures; refer to the specific hole saw manufacturer's data sheet for the cutting saw being used. The trend matters more than the exact numbers — most users run hole saws far too fast. The single most common hole saw mistake: running on full drill speed regardless of diameter. A cordless drill on full trigger spins 2,000+ RPM. A 75 mm hole saw at 2,000 RPM will glaze its teeth in 30 seconds — the saw is destroyed before it has cut through. Slow the drill to half-trigger or less; the cut should sound like sawing, not whining. Variable-speed drills with electronic speed control hold the lower RPM under load. Fixed-speed drills don't — for serious metal cutting, a low-RPM drill press or a drill with a 2-speed gearbox in low gear is the right tool. Common Hole Saw Sizes and What They're Used For Hole saws come in graduated diameters; certain sizes are far more common than others because they match standard fittings, fixtures, and openings. Diameter Common application 17–25 mm Conduit entries (20 mm conduit), cable glands, small electrical fittings 25–32 mm Cable glands (25 mm), Cat6 wall plates, small downlights 32–40 mm Larger conduit, electrical socket boxes, plumbing pipe entries 40–54 mm Door lock cylinder bores, pipe through-holes, small recessed lights 54–70 mm Door knob latches (54 mm bore + 25 mm latch), exhaust fan openings 70–80 mm Standard downlight openings (70 mm and 76 mm AU standard sizes) 80–92 mm Larger downlights, sub-floor vents, switchboard cable entries 92–100 mm Recessed light fittings, vent ducts, conduit entries 100–127 mm Large vents, range hood ducting (100 mm), spa pipe through-holes 127–200 mm Large duct work, industrial pipe through-holes, specialty applications The downlight standard Australian recessed downlight fittings standardise on a small set of cut-out sizes — predominantly 70 mm and 76 mm for residential downlights, with 90 mm and 92 mm common in commercial. Electricians fit-out new homes cutting hundreds of these holes; specifying the downlight before specifying the hole saw is faster than the reverse. Conduit-to-hole-saw sizing for electricians The hole-saw size for an AU electrical conduit is not simply the conduit diameter — gland nuts and conduit fittings need clearance. Common AU electrical conduit sizes and the matching hole-saw diameter: Conduit nominal size Conduit OD (mm) Hole-saw diameter 16 mm ~16 20 mm 20 mm ~20 25 mm 25 mm ~25 32 mm 32 mm ~32 40 mm 40 mm ~40 50 mm 50 mm ~50 60 mm The hole-saw size matches the gland-nut OD plus small clearance, not the conduit OD. Always confirm against the specific gland-nut manufacturer data sheet — a few millimetres difference between brands is common. Selecting a Hole Saw for Your Material The four-factor selection process: Identify the material exactly. "Steel" isn't enough. Mild steel, stainless 304, stainless 316, hardened tool steel, cast iron, and Galvalume all need different hole saws or speeds. "Wood" isn't enough either — softwood, hardwood, treated pine, MDF, and plywood respond differently. Identify the material thickness. Hole saw cup depth (typically 38–50 mm) limits the maximum cut depth. Thicker material requires multi-step cutting from both sides or a different tool (annular cutter, plasma). Match hole saw type to material. Use the table earlier: bi-metal for wood/mild steel, TCT for stainless and hard steel, diamond for tile/glass, masonry-grade for brick/concrete. Specify the diameter. Match the application — fitting standard, fixture standard, or mating part dimension. For mixed-material applications (multi-purpose TCT), pick the hardest material in the mix as the limiting factor. A TCT multi-purpose hole saw handles wood, fibre cement, and stainless in succession; a bi-metal would dull on the stainless cut. Hole Saw Arbors and Mandrels The hole saw itself doesn't fit a drill chuck — it threads onto an arbor (also called a mandrel) which holds the pilot drill and connects to the drill chuck. The arbor is often forgotten in first-time hole saw purchases. Arbor types and compatibility Universal arbor — fits a range of hole saw sizes via a threaded back. Sutton's H112UA2 universal arbor at AIMS fits hole saws 32–54 mm; smaller arbors handle 14–30 mm; larger arbors above 54 mm. Most users own two arbors covering the small and large size ranges. Quick-change / quick-fit arbor — proprietary connection allowing fast hole saw swapping without unthreading. Convenient for high-volume work; locks the user into one brand's hole saw range. Hex shank / SDS arbor — for use in impact drivers (hex) or rotary hammers (SDS). Less common; check drill compatibility first. Pilot drill The pilot drill in the arbor centre locates the hole saw cut and prevents the saw from "walking" across the surface before the teeth engage. Standard pilot drills are HSS twist drills 6–10 mm diameter. They wear out with heavy use; replacement pilot drills are available separately. Use a short pilot drill — screw-machine-length or stub-length, not a standard jobber-length. Long pilot drills wander off-centre as the saw begins cutting, especially in cordless drills with hand-held alignment. Short pilots stay rigid and on-mark. For production-volume work, drill-guide bushings (a hardened steel sleeve clamped to the workpiece, pilot drill running through the sleeve) eliminate wander entirely — the right setup for cutting hundreds of identical holes. For one-off and small-batch workshop cuts, clamping the workpiece in a bench vice is the standard approach. A vice provides solid, hands-free stability and eliminates the spinning-plate hazard that occurs when a hole saw catches in unsecured sheet or thin plate material. Cutting Technique — Pilot Drill, Pressure, Cooling A correctly-specified hole saw cuts cleanly when used correctly. Common technique steps: Step 1 — Mark the centre and pilot Mark the cut centre with a punch (centre punch on metal, awl on wood, marking pen on tile). Position the pilot drill on the mark. Confirm the hole saw is square to the surface. Step 2 — Start at low RPM Begin cutting at the slowest reasonable RPM — pilot drill engages, hole saw teeth start kerf. Once the kerf is established (visible groove), maintain that RPM through the cut. Don't speed up. Step 3 — Apply moderate, steady pressure Push hard enough that each tooth takes a chip. Too light = teeth skate, glazing the cut. Too heavy = teeth break or the drill stalls. The right pressure makes a steady cutting noise (sawing sound, not whine, not chatter). The single most damaging mistake — excessive feed pressure. Manufacturer data from Morse, Starrett and others consistently identifies excessive feed pressure as the number-one cause of damaged hole saws. Push hard enough that each tooth takes a chip; not so hard that the drill stalls or chatters. If the drill is bogging down or you are putting your weight behind it, you are over-feeding — broken teeth follow within seconds. Step 4 — Cool the cut on metal For mild steel, stainless, and aluminium, apply cutting fluid (CRC Tap-X, Trefolex, or equivalent) directly into the kerf. The fluid cools the teeth, lubricates the chip, and prevents tooth glazing. For diamond hole saws on tile, water cooling is mandatory — flooding the cut. Counter-intuitive on stainless: stainless steel needs FIRM feed pressure despite the slow RPM. Light pressure on stainless lets the hard chromium-bearing surface work-harden under the tooth tips, glazing both the workpiece and the saw. Push enough to keep each tooth biting fresh material; the cut should produce continuous chips, not glittery dust. Step 5 — Clear chips regularly Withdraw the saw every few millimetres of cut depth to clear chips from the kerf. Trapped chips cause heat build-up, glazing, and slug-jamming inside the cup. On metal, chip clearing every 30 seconds is reasonable. Step 6 — Slow down at break-through As the saw approaches the back surface, reduce pressure. Punching through at full pressure causes burr-out on the exit side and risk of breaking the pilot drill or rim teeth. Step 7 — Eject the slug The cut "slug" is held inside the saw cup. Eject through the saw's slot or with a punch through the rear hole; never with a hammer on the saw teeth. Common Failure Modes — and How to Avoid Them Glazed teeth (smooth, polished, won't cut) Cause: too high RPM, insufficient cutting pressure, no cutting fluid on metal. Once teeth glaze, the saw is finished — re-sharpening hole saws isn't economic. Fix: replace the saw; for the next cut, slow the RPM, increase pressure, and apply cutting fluid. Broken teeth (chunks missing from rim) Cause: too high cutting pressure, hitting embedded fastener or rebar mid-cut, dropping the saw. Fix: replace the saw; check the cut path for hidden fasteners or hardened inclusions; reduce pressure if drill is stalling. Slug stuck in the cup Cause: heat-welded, swarf-jammed, or normal interference fit on a clean cut. Three removal techniques in order of preference: (1) run the drill briefly in reverse — half a second of reverse rotation often breaks the slug free without any other intervention; (2) tap with a punch through the rear hole on the arbor — for hot-stuck slugs (welded), let cool first then tap; (3) for repeat sticking on the same job, install a slug-ejection spring inside the cup — pushes the slug out automatically as the saw withdraws. Walking / pilot drill skipping Cause: pilot drill blunt or worn; surface too smooth (polished steel, glazed tile); insufficient centre punch. Fix: replace pilot drill; punch a deeper centre dimple before cutting; use a bushing jig for production work. Smoke and burning at cut Cause: temperature too high — usually wrong RPM (too fast) or no cooling fluid. Fix: stop, let the saw cool, slow the RPM, apply cutting fluid before resuming. When NOT to Use a Hole Saw An honest specification guide should call out where hole saws are the wrong tool. Six situations where another method is correct: Material thicker than the cup depth (typically >50 mm). Hole saws can't cut deeper than their internal cup length. For deeper holes, use an annular cutter (purpose-built for thicker steel up to 100 mm) or step-cut from both sides. Production-volume metal cutting. Annular cutters are 3–5× faster than hole saws in steel and last longer. For high-volume hole drilling on the same machine, annular cutters with magnetic-base drill rigs are the right tool. Holes smaller than 14 mm. Small hole saws exist but twist drill bits are simpler, faster, and longer-lasting at small diameters. For graduated 4 mm to 35 mm holes in thin sheet metal, step drill bits are usually the right tool — see our Step Drill Bit Guide. Holes in living rebar-reinforced concrete. Diamond core drills with water cooling, or impact-rated SDS bits with hammer action, handle reinforced concrete. Masonry hole saws stop at the rebar. Cutting holes in safety glass, tempered glass, or laminated glass. These materials shatter or delaminate under hole saw pressure. Specify a glass-specific drill or have the holes cut by the glass supplier before tempering. Cutting through electrical cables, water pipes, or unknown services within walls/floors. Use a stud finder, wire detector, or cable scanner first. Hole saws cut blind into services with serious consequences — flooded floors, electrocution risk. Hole Saw Brands in Australia The AU hole saw market spans four broad tiers. Match the brand to the use intensity. Tier Brands Best for Premium engineered Starrett, Lenox, Milwaukee Hole Dozer, Bosch Pro High-volume professional work; specialist applications (extremely hard steel, exotic materials) Industrial / trade Sutton (AU brand), Irwin, DeWalt, Makita Daily trade and workshop use — electricians, plumbers, fabricators Mid-range / DIY Toolpro, Tactix, house brands Occasional DIY use, light renovations Consumer / supermarket Generic imports Single-use applications; one-off home jobs Sutton Tools is an Australian-manufactured cutting tool brand based in Melbourne — bi-metal cobalt hole saws (the H125 series) are stocked across the AU industrial supply chain and are the trade default for electricians, plumbers, and HVAC fitters. The Australian manufacture means consistent metallurgy, short supply chain, and AU-standard sizing. Premium brands (Starrett, Lenox, Milwaukee) earn their price in high-volume professional work — site-installation crews cutting hundreds of downlight openings per week, or fabricators in heavy stainless. For mid-volume trade work, Sutton or equivalent industrial-grade is the right balance. AIMS Industrial Hole Saw Range AIMS stocks hole saws and accessories across the Sutton bi-metal cobalt range plus arbors and pilot drill replacements. The full range — H125 series in 14–127 mm diameters, universal arbors, accessories — is in the Hole Saws & Accessories collection. For sourcing larger diameters, TCT or diamond grit hole saws not in stock, or arbors matched to specific drill chucks, contact the AIMS team. Companion guides: for the broader drill bit range and selection, see our Drill Bit Types Guide; for graduated sheet-metal holes in 4–35 mm sizes, see the Step Drill Bit Guide; for cutting speed and feed reference across drill bits, taps and lathe operations, see the Drill Speed Chart; for drill bit sizing in metric and imperial, see the Drill Bit Size Chart. Related AIMS Selectors This hole saw guide pairs with AIMS's other drilling and cutting selectors: Drill Bit Size Selector — for hole sizes below 16mm (where twist drills work best), every metric drill diameter linked to AIMS SKU. Drill Bit Selection Guide — broad guide on drill bit selection by material. Cobalt Drill Bit Guide — for stainless steel drilling, cobalt drills outperform bi-metal hole saws on smaller diameters. Tap Drill Size Selector — for threading work after drilling. Cutting Speeds & Feeds Reference — RPM by hole diameter and material. Cutting Tool Materials — HSS, bi-metal, TCT, diamond grades compared. Cutting Tool Troubleshooting — wandering, vibration, premature tooth wear. Or browse the full hole saws + accessories range — 130 products including Bordo XP kits, Sutton single hole saws, arbors, pilot drills and diamond holesaws. Next-day Australia-wide dispatch from our Milperra warehouse.Frequently Asked Questions What is a hole saw? A hole saw is a cylindrical drilling tool that cuts a circular hole by sawing the perimeter rather than removing all the material in the hole. The cup-shaped saw has cutting teeth around its open mouth and a centre pilot drill that locates the cut. As the tool spins, the teeth cut a circular kerf; the material inside the kerf — the core or slug — comes out intact when the cut breaks through. Hole saws cut diameters from 14 mm to 200+ mm in materials including wood, mild steel, stainless steel, aluminium, plastic, fibre cement, tile, glass, and masonry — using different cutting tooth materials (bi-metal HSS, tungsten carbide, diamond grit, masonry carbide) matched to the substrate. What's the difference between a bi-metal and a carbide hole saw? Bi-metal hole saws have HSS teeth on a spring-steel body — the workshop default for wood, plasterboard, mild steel up to 6 mm, aluminium, and brass. Tungsten carbide-tipped (TCT) hole saws have hardened carbide cutting edges brazed to the saw body — used for stainless steel, hardened steel, cast iron, fibre cement, and abrasive composites where bi-metal teeth dull quickly. TCT costs 2–3× bi-metal but lasts 3–5× longer in stainless and abrasive materials. Choose bi-metal for general workshop and trade use; specify TCT when bi-metal can't cut the material or when production volume justifies the longer life. What RPM should I run a hole saw at? Hole saw RPM is inversely proportional to diameter — bigger diameter, slower RPM. Bi-metal in mild steel: 20 mm = ~400 RPM, 50 mm = ~160 RPM, 100 mm = ~80 RPM, 150 mm = ~50 RPM. Stainless steel TCT: roughly half those RPMs (slower for harder material). Wood with bi-metal: roughly 4× the steel RPMs (faster for softer material). The single most common mistake is running a hole saw at full drill speed regardless of diameter — a 75 mm hole saw at 2000 RPM glazes its teeth in 30 seconds. Slow the drill; the cut should sound like sawing, not whining. What hole saw cuts stainless steel? Stainless steel needs tungsten carbide-tipped (TCT) hole saws — bi-metal HSS teeth dull on stainless within a few cuts. Use cutting fluid (CRC Tap-X, Trefolex, or equivalent) directly in the kerf for cooling and lubrication. Run very slow RPM — for a 50 mm hole in stainless, 50–60 RPM is the right range. Apply firm steady pressure (light pressure causes glazing on stainless). Withdraw to clear chips every few millimetres of cut depth. The same TCT hole saws that work on stainless also handle mild steel and aluminium — over-spec but no performance penalty. What hole saw cuts tile? Diamond grit hole saws cut ceramic tile, porcelain, glass, and stone. The diamond grit abrades the material rather than sawing it. Critical: diamond hole saws must be flooded with water during cutting — dry cutting destroys the saw within minutes by causing diamond loss and substrate cracking. Run slow RPM (typically 200–600 RPM depending on diameter and material). Use light pressure — let the diamond grit do the work. Tile cuts can be made dry with very small diameter saws and short cuts but professional tile work flood-cools every cut. How long does a hole saw last? Service life varies enormously by hole saw type, material being cut, and operator technique. Bi-metal hole saws in plasterboard or wood: thousands of cuts. Bi-metal in mild steel: 100–500 cuts depending on grade. Bi-metal in stainless: 5–20 cuts before glazing. TCT in stainless: 50–200 cuts. Diamond in tile: 30–80 cuts depending on tile hardness. Operator technique (correct RPM, cutting fluid, chip clearing) can double or triple these figures; running too fast or dry can cut them by 90%. Budget plan: bi-metal as service item replaced at noticeable performance drop; TCT and diamond as longer-lived but specialist tools. Can I cut concrete with a hole saw? Yes — with a tungsten carbide masonry hole saw and a hammer drill or rotary hammer. Standard rotary drills don't have enough impact action to cut masonry effectively; the drill must hammer as it rotates. Masonry hole saws are distinct from TCT metal hole saws — different carbide grade, different tip geometry. They cut brick, concrete, and blockwork but stop at reinforcing steel — hitting rebar requires a separate metal hole saw to clear. For deep holes through reinforced concrete, diamond core drills with water cooling are the professional answer. What size hole saw for a downlight? Australian recessed downlight fittings standardise on a small set of cut-out sizes — predominantly 70 mm and 76 mm for residential downlights, with 90 mm and 92 mm common in commercial fittings. Always confirm the cut-out size from the specific downlight manufacturer's data sheet before cutting — wrong size means the fitting either falls through or doesn't fit. Most electricians keep a Sutton or equivalent bi-metal hole saw in 70 mm, 76 mm, 90 mm, and 92 mm in their van for residential and commercial fit-outs. What is a pilot drill on a hole saw? The pilot drill is the small twist drill bit at the centre of the hole saw arbor. It locates the hole saw cut on the surface and prevents the saw from "walking" across the surface before the teeth engage. Standard pilot drills are HSS 6–10 mm diameter; they cut a small centre hole that the hole saw teeth then enlarge to full diameter. Pilot drills wear out with heavy use — replacement pilot drills fit standard arbors. Without a working pilot drill, the hole saw drifts off-centre at start; the resulting hole isn't where the centre punch was. What is a hole saw arbor? The arbor (also called a mandrel) is the connector between the drill chuck and the hole saw — the saw threads onto the arbor at one end, and the arbor's hex shank fits the drill chuck at the other end. The pilot drill mounts in the arbor centre. Universal arbors fit a range of hole saw sizes via standard threads; quick-change arbors use proprietary connections for fast swapping. Arbors are sized for hole saw diameter ranges — small (14–30 mm), medium (30–54 mm), and large (54+ mm) typical. Most workshops own two or three arbors covering the diameter ranges they use; buying a hole saw without checking arbor compatibility is a common first-time purchase mistake. Why does my hole saw smoke / burn? Smoke from a hole saw means temperature too high — usually wrong RPM (running too fast for the diameter) or no cooling fluid on metal cuts. Stop immediately, let the saw cool, slow the drill speed, and apply cutting fluid (CRC Tap-X or equivalent) before resuming. Continued cutting with a smoking saw glazes the teeth (smooth polished cutting edges that won't cut) — once glazed, the saw is finished. The cut should sound like steady sawing, not whining; smell the cut — burning smell means something is wrong. Why is my hole saw stuck — slug won't come out? The cut slug stuck in the saw cup is normal — interference fit on a clean cut, swarf-jammed on metal, or heat-welded on hot cuts. Eject through the rear hole on the arbor with a punch tap (tap, don't hammer hard, against the slug from behind). For hot-welded slugs, let cool fully first; trying to eject a hot slug warps the saw cup. For repeat sticking on the same job, install a slug-ejection spring inside the cup — pushes the slug out automatically as the saw withdraws. Can I sharpen a hole saw? Bi-metal hole saws can technically be sharpened on a tooth grinder, but it's rarely economic — the labour to sharpen a 60 mm bi-metal hole saw professionally costs more than a new one. TCT hole saws can be re-tipped at specialist tool sharpening services; only justified for premium-grade saws used in specialist applications. Diamond hole saws aren't sharpened — when the diamond grit is worn, the saw is replaced. For the vast majority of hole saw users, replacement at end-of-life is faster and cheaper than re-sharpening. What's the difference between a hole saw and an annular cutter? Both cut circular holes by sawing the perimeter. Hole saws use teeth all around the cup mouth; annular cutters have a different tooth geometry (chip-clearing slots and a precise rim) plus a coolant-fed centre. Annular cutters cut faster in steel (3–5× a hole saw), produce a cleaner edge, last 10–20× longer, and handle thicker material (up to 100 mm depth versus hole saw's 50 mm limit). Trade-offs: annular cutters need a stronger drill (typically a magnetic-base drill rig), cost more per cutter, and aren't suitable for wood. For high-volume metal cutting, annular cutters; for general workshop and trade use, hole saws. Where can I buy hole saws in Australia? AIMS Industrial stocks the Sutton (Australian-manufactured) bi-metal cobalt hole saw range across 14–127 mm diameters, plus universal arbors and accessories. The dedicated Hole Saws & Accessories collection covers the full Sutton range. For premium brands (Starrett, Lenox, Milwaukee) specialist tool retailers and Total Tools / Sydney Tools stock the range. For consumer DIY use, Bunnings and similar carry house-brand and Toolpro / Tactix grade saws. Match the brand tier to the use intensity — daily trade and workshop use justifies the Sutton industrial tier; one-off home jobs are fine on consumer-grade. Cross-reference our Pulley Speed Ratio guide for the V₂ = V₁ × (D₁ ÷ D₂) formula and worked examples. People Also Ask — Hole Saws Q: How do I cut a hole deeper than my hole saw's cutting depth? Standard hole saws have a limited cutting depth — typically 38mm to 51mm — which is not enough for thick timber, multiple laminated sheets, or deep sections. For deeper cuts, a step-cutting technique is used: make the initial cut to the hole saw's full depth, remove the plug (if it hasn't fallen free), flip the workpiece over and complete the cut from the other side using the pilot hole as a guide. For material that cannot be flipped, an arbor extension can sometimes be used to increase reach, though this reduces rigidity. Purpose-made deep-cut hole saws with taller cups are also available for timber applications where extra depth is regularly needed. Q: What arbor and pilot drill size do I need for a large hole saw? Hole saw arbors come in standard sizes matched to hole saw thread sizes — most hole saws up to approximately 152mm (6") use a standard arbor, while larger hole saws often require a heavy-duty arbor with a larger shank. The pilot drill (also called a mandrel drill) on most arbors is 6mm diameter, suitable for marking and guiding the hole saw through most materials. Larger arbors for big hole saws often use an 8mm or 10mm pilot. When selecting an arbor, check that the shank size matches your drill chuck (typically 3/8" or 1/2" chuck capacity) and that the arbor thread is compatible with your hole saws. Q: Should I use cutting fluid when cutting with a hole saw in metal? Yes — cutting fluid or oil is strongly recommended when using hole saws on mild steel, stainless steel, and other metals. The hole saw generates significant heat at the cutting teeth due to the large contact area, and without lubrication the teeth can overheat, lose their set, and blue or weld to the workpiece. Applying cutting oil to the tooth ring before and during cutting extends tooth life significantly. For thin sheet metal, a light oil or even a spray lubricant can be applied; for heavier plate, brush-on cutting fluid or paste compounds work well. Aluminium benefits from cutting fluid to prevent chips from welding to the teeth. Q: Why does the plug keep getting stuck inside my hole saw? Plug ejection from hole saws is a common frustration. Most hole saws have side slots that allow a screwdriver or rod to be inserted to lever the plug out — this is the intended removal method. To prevent sticking, avoid cutting all the way through the material with continuous pressure; instead, withdraw the hole saw periodically to clear chips. Some arbors include a spring-loaded plug ejector that pushes the slug out when the arbor button is pressed. For timber, the plug tends to jam more firmly than in metal due to wood fibre compression; working it loose by rocking the saw slightly before withdrawal reduces the problem. Q: What hole saw size should I use for electrical conduit? The correct hole saw size for electrical conduit depends on whether you are cutting for the conduit to pass through (clearance hole) or to mount a conduit fitting flush. Conduit is specified by nominal trade size, and the actual outside diameter differs from the nominal size. For example, 20mm nominal conduit typically has an OD of approximately 25mm, requiring a 32mm hole saw for a clearance pass-through. Conduit fittings specify the required knockout or hole diameter on their packaging. When in doubt, measure the conduit or fitting OD directly and add 2 to 3mm clearance — using a hole saw that is too small requires enlarging the hole; slightly too large is generally acceptable. Related AIMS Industrial Engineering References Pair this guide with the AIMS engineering reference cluster for material identification, cutting parameters and tool material selection. Phase 4 master references (universal engineering data): Workpiece Material Cross-Reference Chart — SAE / AISI / DIN / JIS / AS/NZS equivalents across 20 material groups Cutting Speeds & Feeds Reference — RPM and feed rate by material and tool type — drilling, milling, tapping, reaming Cutting Tool Materials Guide — HSS, HSS-Co, PM-HSS, solid carbide, PCBN and PCD explained Cutting Tool Coatings Guide — TiN, TiCN, TiAlN, AlCrN and premium coatings with application matrix Cutting Tool Troubleshooting Guide — 33 symptoms diagnosed across drills, taps, endmills, reamers and bandsaw blades Metric to Imperial Conversion Chart — mm, inches, drill # and gauge cross-reference Sister selection guides in the AIMS application cluster: AIMS Drill Bit Selection Guide — HSS / cobalt / carbide / masonry / tile selection by material and application AIMS Tap & Die Selection Guide — Hand, spiral point, spiral flute and forming taps — metric and imperial For purchase advice, technical questions or items not currently listed, ring AIMS Industrial on (02) 9773 0122 or use the contact page. Trade accounts and bulk pricing available. Need carbide drill bits? Browse the AIMS range at carbide drill bits. For sutton tools, see our sutton tools range stocked across Australia.
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