Product Guides
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.
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Cutting Tool Troubleshooting Guide: Drills, Taps, Endmills, Reamers, Bandsaw Blades
Master troubleshooting reference for cutting tool failures — drills, taps, endmills, reamers, bandsaw blades. Symptom × cause × solution tables plus three universal principles that solve most failures.
Read moreCutting Speeds & Feeds Reference Chart: Drilling, Milling, Tapping, Reaming
Master cutting parameter reference — Vc and feed rate ranges for HSS, cobalt and solid carbide tooling across all major engineering materials. Includes drilling, milling, tapping, reaming and material-specific cautions.
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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