The drill bit that's right for the job depends on three things: the workpiece material, the operation type and the cost-per-hole budget. A general-purpose HSS jobber drill from Sutton Tools or Bordo will get you through mild steel, aluminium and timber at the lowest cost per drill. Stainless steel and harder alloy steels demand cobalt HSS (HSS-Co). Hardened steel above 40 HRC, dry production work or anything requiring 500+ holes from a single bit needs solid carbide. Concrete, brick and stone require carbide-tipped masonry bits used in a hammer or SDS drill. Tile, porcelain and glass require diamond-coated or spear-point glass drill bits — never use a standard twist drill on glazed surfaces.
This guide walks through every drill bit family AIMS stocks, when to use each, what point geometry to specify, which coating helps in which scenario, and which brand wins where. We're explicit about brand strengths: Sutton Tools owns engineering-grade HSS, HSS-Co and solid carbide. Bordo owns specialty drilling (tile, glass, masonry, multi-purpose) and offers a strong HSS range. P&N is the AIMS masonry specialist. We'll recommend across all three honestly — not push a single supplier.
Quick Reference: Drill Bit Material vs Workpiece Material
The fastest way to choose. Match workpiece in the left column to the recommended drill bit material in the right column. The "cost tier" gives an honest indicator of relative drill cost (not per-hole cost — carbide costs more upfront but often costs less per hole at production volume).
| Workpiece Material | Recommended Drill Bit Material | Cost Tier | Typical AIMS Range |
|---|---|---|---|
| Mild steel (M-series, S275, 1018-1020) | HSS or HSS-Co 5% | $ | Sutton D102 / Bordo 2000-series |
| Medium carbon steel (1045, EN8) | HSS-Co 5% or 8% | $$ | Sutton D108 / Bordo Cobalt |
| Stainless steel (304, 316) | HSS-Co 5-8% MANDATORY | $$ | Sutton D108 / Bordo Cobalt |
| Alloy steel (4140, 4340 <30 HRC) | HSS-Co 8% or PM-HSS | $$$ | Sutton D109 Heavy Duty |
| Hardened steel (>40 HRC) | Solid carbide (VHM) coated | $$$$ | Sutton D300-D335 series |
| Cast iron (grey, ductile) | HSS or solid carbide | $-$$$$ | Sutton or Bordo HSS / solid carbide for production |
| Aluminium (most alloys) | HSS bright finish or solid carbide | $-$$$$ | Sutton Aluminium-series / VHM uncoated |
| Brass / copper | HSS bright finish (drill on slow speed) | $ | Sutton HSS jobber |
| Titanium / Inconel / nickel alloys | PM-HSS or coated solid carbide | $$$$$ | Special order — contact AIMS |
| Concrete / brick / mortar | Carbide-tipped masonry drill (TCT) | $ | P&N / Bordo masonry sets |
| Concrete & reinforcing — high impact | SDS-Plus or SDS-Max carbide-tipped | $$ | P&N SDS / Bordo SDS |
| Ceramic tile / porcelain tile | Diamond-coated or spear-point carbide | $$ | Bordo Tile & Porcelain range |
| Glass | Diamond-coated or spear-point carbide | $$ | Bordo Glass range |
| Hardwood / softwood | HSS or brad-point timber bit | $ | Sutton HSS / Bordo timber range |
| Stainless sheet (small holes) | Cobalt HSS step drill | $$ | Step drill range — Sutton / Bordo |
| Sheet steel (variable sizes) | HSS-Co step drill | $$ | Step Drill Bits range |
For deeper material-by-material data including SAE/AISI/DIN/JIS/AS/NZS equivalent grades, see the Workpiece Material Cross-Reference Chart.
The Six Drill Bit Material Families
Every drill bit AIMS stocks is built around one of six tool material families. Understanding which family applies to your job is the most important decision — everything else (sub-type, coating, brand) flows from it.
1. HSS — High-Speed Steel (the workhorse)
HSS is the baseline drill bit material. It cuts mild steel, aluminium, brass, copper and timber reliably at moderate cutting speeds. Hardness around 850 HV at room temperature, dropping to about 200 HV at 500 °C — which is why HSS loses its edge fast when the bit gets hot. Keep cutting speed moderate, use lubricant, and HSS will deliver hundreds of holes per bit on suitable materials.
Buy HSS for: general workshop drilling, home and light-trade use, mild steel under 200 HB, aluminium, brass, timber, plastic.
Don't buy HSS for: stainless steel (the bit will glaze and stop cutting almost immediately), hardened steel, production runs above 100 holes per shift.
AIMS-stocked HSS drills: Sutton D102 jobber range (mild-steel-focused), Bordo 2000-series, Sutton imperial fractional range. Browse jobber drill bits or the broader drilling collection.
2. HSS-Co — Cobalt High-Speed Steel
Adding 5% or 8% cobalt to the HSS alloy doubles the hot hardness. HSS-Co retains around 350 HV at 600 °C (HSS keeps only 200 HV). That makes HSS-Co the correct choice for stainless steel (which work-hardens the moment the bit slows down), harder alloy steels and intermittent cutting where the bit experiences thermal shock.
HSS-Co 5% (sometimes labelled M35) is the entry tier — the right choice for 304 stainless and 1045 medium carbon. HSS-Co 8% (M42) is the next step up for tougher alloys, 316 stainless and heavy production work.
Buy HSS-Co for: stainless steel (mandatory — do not use plain HSS), alloy steel under 30 HRC, harder mild steels (1045, EN8), intermittent or interrupted cuts.
Why a cobalt drill costs roughly 50-100% more than HSS: the cobalt content survives the cutting heat that destroys plain HSS edges in stainless. The cost per drill is higher, but the cost per stainless hole is dramatically lower.
AIMS-stocked HSS-Co drills: Sutton D108 series (M35 cobalt), Sutton D109 Heavy Duty (M42 cobalt), Bordo Cobalt range. Browse cobalt drill bits. For an in-depth look at M35 vs M42 selection, see the Cobalt Drill Bit Guide.
3. Solid Carbide (VHM)
Solid carbide drills — "VHM" in European catalogues — are made entirely from sintered tungsten carbide. Hardness around 1,400 HV at room temperature, holding 1,200 HV at 600 °C. That's the same temperature where HSS has collapsed to 200 HV.
What this buys you: cutting speeds 3-5× higher than HSS, tool life 5-10× longer, the ability to drill hardened steel (over 40 HRC) and the ability to run dry or with minimum-quantity lubrication. The trade-off: solid carbide is brittle. A chipped cutting edge from an interrupted cut, an unstable workpiece or shock load can shatter the drill. Solid carbide demands a rigid machine setup (CNC, mag drill or sturdy pillar drill — not handheld) and steady feed rates.
Buy solid carbide for: hardened steel (over 40 HRC), production volume drilling (500+ holes per drill), dry or MQL machining, high-speed work, CNC applications.
Don't buy solid carbide for: handheld drilling, interrupted cuts, low-volume one-off jobs (cost won't be recovered), shock-prone applications.
AIMS-stocked solid carbide drills: Sutton D300-D335 series across uncoated, TiAlN-coated and AlCrN-coated variants. Bordo carbide range covers specialty sizes. Browse the carbide drill bits collection. For the cost-vs-life economics, see Carbide vs HSS.
4. Carbide-Tipped (TCT)
TCT — tungsten carbide tipped — drills use a steel body with brazed carbide cutting tips. They're a cost-efficient bridge between HSS and solid carbide: most of the drill is cheap steel, only the cutting tip is the expensive carbide. The wear advantage is concentrated where you need it.
TCT is the standard architecture for masonry drills (concrete, brick, stone), multi-material drills (the "drill anything" bits that genuinely work on tile, brick AND steel) and some larger-diameter wood drills.
Buy TCT for: masonry, concrete, brick, tile when paired with the right point geometry, multi-material drilling.
AIMS-stocked TCT drills: P&N masonry range, Bordo masonry and multi-purpose ranges. Browse the masonry drill bits collection.
5. Diamond & Spear-Point (tile, glass, porcelain)
Standard twist drills cannot cut ceramic tile, porcelain or glass. The bit skates across the glaze, then shatters the workpiece when it bites. For these materials you need either:
- Diamond-coated drill bits — abrasive cutting (not cutting in the conventional sense). Used for porcelain tile, glass and stone. Require water cooling.
- Spear-point carbide drills — a single-flute carbide point ground to a sharp spear shape. Designed for glass and softer tile. Lower price than diamond, lower lifespan.
Buy diamond/spear-point for: ceramic tile, porcelain tile, glass, mirror, light stone work.
AIMS-stocked range: Bordo Tile, Bordo Porcelain and Bordo Glass ranges. These specialty bits sit alongside our masonry drill bits for tradies who need both in the same kit.
6. Masonry & Hammer Drill Bits (SDS, SDS-Plus, SDS-Max)
Masonry drilling into concrete demands impact assistance — rotation alone won't cut hardened concrete fast enough. The two architectures:
- Rotary-hammer masonry bits — standard 6mm shank for use in any combi or hammer drill. Suitable for brick, mortar, light concrete.
- SDS-Plus and SDS-Max — specialised shank systems that lock into a dedicated SDS rotary hammer. The shank transmits hammer energy more efficiently to the carbide tip. SDS-Plus for general concrete up to 32mm hole; SDS-Max for heavy concrete and rebar work above 25mm.
AIMS-stocked range: P&N SDS-Plus range (the AIMS masonry specialist), Bordo SDS, Bordo standard masonry. Browse the masonry drill bits collection.
Drill Bit by Application — Quick Selector
Workpiece-based selection. Match the application you're doing to the drill bit family, point geometry and coating. For deeper cutting parameter data (speed RPM, feed mm/rev), see Cutting Speeds & Feeds Reference.
| Application | Drill Material | Point Angle | Coating | Lubrication |
|---|---|---|---|---|
| General mild steel & aluminium | HSS | 118° standard | Bright (uncoated) | Soluble oil or none for aluminium |
| Stainless steel sheet & plate | HSS-Co 5-8% | 135° split point | TiAlN or bright | Heavy soluble oil — mandatory |
| Heavy production mild steel | HSS-Co 8% or solid carbide | 135° split point | TiN or TiAlN | Through-coolant if available |
| Hardened steel (over 40 HRC) | Solid carbide | 140° split point | AlCrN mandatory | MQL or dry — carbide doesn't need flood coolant |
| Cast iron (grey or ductile) | HSS-Co or solid carbide | 118° standard | Bright or TiN | Dry — cast iron dust is the lubricant |
| Aluminium (production) | Solid carbide uncoated | 118° or 140° sharp | Uncoated (TiAlN catalyses with Al) | MQL or flood — chip evacuation critical |
| Brass / copper | HSS bright | 118° or zero-rake | Bright | Light oil — brass cuts cleanly |
| Stainless / heat-resistant alloys | PM-HSS or solid carbide | 135° split point | TiAlN or AlCrN | Flood coolant — never let the bit slow |
| Concrete / brick / mortar | Carbide-tipped (TCT) | Specialty masonry point | Carbide brazing | None — impact-driven |
| Hard concrete + rebar | SDS-Plus or SDS-Max | Specialty | Carbide brazing | None |
| Ceramic tile (glazed) | Diamond-coated | N/A (abrasive) | Diamond grit | Water cooling — mandatory |
| Porcelain tile | Diamond-coated only | N/A | Diamond grit | Water cooling — mandatory |
| Glass | Spear-point carbide or diamond | Spear | None or diamond | Water or oil — mandatory |
| Hardwood (deep holes) | HSS twist or auger | 118° or specialty | Bright | None |
| Variable hole sizes in sheet | HSS-Co step drill | Specialty stepped | TiAlN typical | Light oil |
If a hole-cutting application is larger than 30mm diameter, consider whether a hole saw is a better choice than a large drill bit — hole saws cut a kerf instead of a full plug and remove material faster on sheet stock.
Drill Bit Sub-Types — Which Length and Shank?
Beyond material, the drill bit's physical configuration matters. The right sub-type depends on hole depth, machine setup and hole accuracy requirements.
Jobber Drill (Default Choice)
The standard general-purpose configuration. Flute length around 9-14× diameter. Suitable for almost all general drilling jobs. Most workshop and trade work uses jobber drills unless a specific reason rules them out.
AIMS stocks 74 jobber drill bit lines across HSS, HSS-Co and solid carbide variants from Sutton Tools and Bordo.
Stub Drill (Rigidity for Accuracy)
Shorter flute (around 4-6× diameter). The shorter unsupported length deflects less, giving better hole position accuracy. Use stub drills for: precision positioning, spot drilling before a larger drill, thin material drilling, when CNC accuracy matters.
Long-Series and Extra-Long Drills
Flute lengths 15-30× diameter for deep holes. The trade-off: long drills deflect more, so hole position accuracy drops and you must drill at lower feed rates. For deep holes consider a stub drill to spot the hole, then a long-series drill to deepen.
Step Drill (One Bit, Multiple Hole Sizes)
A stepped cone of sequential drill diameters on a single bit. Designed for sheet metal where you might want a 4mm pilot then a 6, 8, 10 or 12mm finished hole. Step drills also self-deburr the hole on the up-stroke.
Buy step drills for: sheet metal cabinet work, electrical box knockouts, automotive panel repair, anything needing variable hole sizes in thin material (under 6mm).
Don't buy step drills for: deep holes (they only work in thin sheet), large-diameter holes, hard materials.
AIMS stocks 22 step drill bit lines across HSS-Co and TiAlN-coated variants. For deeper coverage see the step drill bit guide.
Reduced-Shank Drill (Large Hole, Small Chuck)
A 25mm drill with a 13mm reduced shank fits a standard 13mm drill chuck while drilling the larger hole. Common bridge between the chuck capacity of a domestic drill (10-13mm) and the larger holes a metalworker occasionally needs.
Centre Drill / Spotting Drill
A short, rigid drill with a 60° or 90° included angle. Used to spot a starting dimple before drilling with the actual production drill — ensures the production drill enters straight and at the correct location. Critical on lathe work and any precision job.
SDS-Plus & SDS-Max (Masonry Specialty)
SDS-Plus and SDS-Max are specialised shank systems for rotary hammer drills. The keyless quick-change shank transmits hammer impact energy directly to the carbide tip. You can't run SDS bits in a standard chuck and you can't run standard masonry bits in an SDS chuck. Match the shank to the machine.
Drill Point Geometry — Which Angle for Which Job?
The drill bit's point angle is the included angle of the two cutting lips. Standard angles are 90°, 118°, 135° and 140° — each suited to different materials. Specialty geometries (spear, brad, masonry, fishtail) serve specific roles.
| Point Angle / Type | Best For | Why |
|---|---|---|
| 118° standard | Mild steel, aluminium, brass, general workshop | The default. Balanced between cutting efficiency and edge strength. |
| 135° split point | Stainless steel, harder alloys, hand-held drilling | Self-centring — the split point bites into hard material without wandering. Reduces walk on flat surfaces. |
| 140° split point | Hardened steel, solid carbide drills | Even more aggressive cutting action; more positive lip engagement for tough materials. |
| 90° (deburring point) | Countersinking, deburring | Used to cut a chamfer for countersunk screw heads — not for drilling holes. |
| Brad point (timber) | Hardwood, softwood | Sharp centre point keeps the drill on location; outer spurs cut a clean shoulder. |
| Spear point (glass / tile) | Glass, ceramic tile, mirror | Single-flute carbide spear — scrapes material rather than cutting chips. |
| Masonry point (TCT) | Concrete, brick, stone | Brazed carbide button tip; impact-driven cutting action. |
| Fishtail point | Spotting drills, lathe spot drilling | Wide chip clearance; positive cut into round stock. |
The most common upgrade decision: if you're drilling stainless steel by hand or on a pillar drill and the standard 118° HSS-Co isn't behaving, switch to a 135° split-point HSS-Co bit. The split point eliminates wandering and forces the drill to bite immediately — preventing the work-hardening that ruins stainless drilling.
For drill point angle and tip geometry data across all standard drill types, the Cutting Tool Troubleshooting Guide diagnoses what wrong point geometry looks like in practice (squealing, walking, premature wear).
Coatings — Which One for Which Job?
Coatings extend tool life by reducing edge wear, improving heat resistance, lowering cutting friction or preventing built-up edge. The coating selected should match the workpiece material — the wrong coating costs you 30-60% of the drill's life. For deep coverage of all 13 PVD coatings, see the Cutting Tool Coatings Guide.
| Coating | Colour | Best For | Avoid |
|---|---|---|---|
| Bright (uncoated) | Silver | Aluminium, brass, copper, soft non-ferrous | Stainless, hardened steel (no heat resistance) |
| Black oxide | Black | Mild steel, general HSS — cost-efficient corrosion finish | Stainless (decorative more than functional) |
| Bronze oxide | Bronze/gold | HSS-Co drills — finish marker, not a true coating | Aluminium (catalyses) |
| TiN — Titanium Nitride | Gold | Mild steel, alloy steel, light stainless | Hardened steel (insufficient hardness) |
| TiCN — Titanium Carbo-Nitride | Grey-blue / blue-violet | Stainless steel, abrasive materials, plastic | High-heat (limited oxidation resistance) |
| TiAlN — Titanium Aluminium Nitride | Black-purple | Hardened steel, stainless, high-temperature drilling | Aluminium (Al-on-Al catalyses) |
| AlCrN — Aluminium Chromium Nitride | Dark grey | Hardened steel up to 65 HRC, premium production work | Cost-sensitive lower-volume work |
| Diamond (CVD or DLC) | Black or grey | Non-ferrous, CFRP, graphite, ceramics | All ferrous materials (catastrophic catalysis) |
The TiAlN-on-aluminium trap: TiAlN is the most popular premium coating for steel and stainless. It does NOT work on aluminium — the aluminium in the coating catalyses with aluminium in the workpiece, causing built-up edge and immediate tool failure. For aluminium, use uncoated bright HSS or uncoated solid carbide. The Cutting Tool Coatings Guide expands on this.
Brands Stocked at AIMS — Honest Selection Guide
AIMS stocks drill bits from multiple manufacturers. Each brand has a specific strength — we'll be explicit about which brand wins where, rather than pushing a single supplier.
Sutton Tools — Engineering-Grade HSS, HSS-Co and Solid Carbide
Sutton Tools is the AIMS dominant brand for engineering drilling. Sutton designs and manufactures locally in Melbourne, supplies the major Australian engineering and tool-room market, and offers the deepest range of HSS, HSS-Co and solid carbide in fractional, metric and imperial sizes. The Sutton D-series catalogue covers:
- D102 — HSS jobber for mild steel and aluminium (entry tier)
- D108 — HSS-Co 5% for stainless and harder alloys
- D109 — HSS-Co Heavy Duty (M42 cobalt) for tough alloys
- D300-D335 — solid carbide variants across uncoated, TiAlN and AlCrN
- Centre drills, spotting drills, reduced-shank drills and long-series drills
For Australian engineering and tool-room work, Sutton is the default choice. Browse the Sutton Tools collection.
Bordo — Multi-Purpose, Specialty and HSS Workshop Range
Bordo is the AIMS go-to for specialty drilling: tile, porcelain, glass, multi-purpose and masonry sets. Bordo also offers a strong general HSS range that competes directly with Sutton's entry tier for lower-volume workshop and trade users. Bordo's strength is range breadth — if a tradie needs a drill that genuinely works on multiple materials in one bit, Bordo's multi-purpose range is the right call.
Browse the Bordo collection (716 products).
P&N — Masonry Specialist
P&N is the AIMS masonry specialist. The P&N range covers SDS-Plus, SDS-Max and standard masonry drills with carbide-tipped construction for concrete, brick and stone. P&N also offers heavier-duty masonry sets for trade and concrete contractor use.
Browse the P&N collection (216 products).
Brand Selection Summary — Pick by Need
| Job Type | Recommended Brand | Why |
|---|---|---|
| Engineering tool-room (mild steel, alloy steel) | Sutton Tools (D102, D108) | Local manufacture, deepest range, engineering grade |
| Stainless steel production drilling | Sutton Tools (D108 HSS-Co) | Cobalt content + Australian engineering reliability |
| Hardened steel (over 40 HRC) | Sutton Tools (D300-D335 solid carbide) | Coated VHM range covers full hardness spectrum |
| Workshop / home / light-trade general use | Bordo HSS or Sutton D102 | Both deliver good value at the entry tier |
| Tile / porcelain / glass | Bordo specialty range | Bordo's specialty depth beats engineering brands |
| Concrete / brick / masonry | P&N (or Bordo masonry sets) | P&N is the masonry specialist; Bordo offers strong sets |
| Multi-material site work | Bordo multi-purpose | Genuine multi-material designs — not all "multi-material" claims are equal |
| SDS-Plus / SDS-Max heavy concrete | P&N SDS or Bordo SDS | Both work; choose by your machine and the wholesaler's current stock position |
For any brand AIMS doesn't currently stock, we can source by special order — ring (02) 9773 0122 or use the contact form.
AIMS-Stocked Drill Bit Range Cross-Reference
Direct links to the AIMS drill bit collections. The numbers in brackets are current stock counts.
- All drilling products (781 lines)
- Jobber drill bits (74)
- Carbide drill bits (15)
- Cobalt drill bits (7)
- Masonry drill bits (64)
- Step drill bits (22)
- Hole saws (130)
- Drill accessories & adaptors (52)
By brand: Sutton Tools · Bordo · P&N · Shop by Brand for the full A-Z directory.
Cost vs Tool Life — Doing the Maths
The cheapest drill bit is rarely the cheapest hole. Drill bit selection is an economic decision — the right comparison is cost-per-hole-machined, not the price ticket on the drill. A worked example for drilling 1,000 holes in 304 stainless:
| Drill Choice | Drill Cost | Holes per Drill | Drill Failures in 1,000 Holes | Cost per Hole |
|---|---|---|---|---|
| HSS jobber (wrong choice for stainless) | $15 | ~5 (work-hardens immediately) | 200 drills | $3.00 |
| HSS-Co 5% (entry cobalt) | $28 | ~80 | 13 drills | $0.36 |
| HSS-Co 8% Heavy Duty | $48 | ~200 | 5 drills | $0.24 |
| Solid carbide TiAlN-coated | $180 | ~3,500 | 1 drill (with spare) | $0.054 |
The right math for production drilling: divide the total drill cost by the holes you'll get from that drill. Add in the machine time wasted swapping drills (each swap is 2-5 minutes lost), and the picture shifts even more in favour of the premium drill.
The right math for one-off jobs: if you need 5 holes in stainless, an HSS-Co drill at $28 is fine. Don't buy a $180 solid carbide drill for one job.
For the deeper economics across cutting tool material families, see the Cutting Tool Materials Guide.
Australian & International Standards Relevant to Drill Bits
Drill bit dimensions, materials and performance are governed by a mix of Australian, ISO, ANSI and DIN standards. The key references:
- ISO 235 — Twist drills with parallel shank: dimensions, tolerances and designation. The international reference standard for HSS twist drill dimensions.
- ANSI B94.11M — Twist drills: dimensions, designations and numerical sizes (#1-#80) plus letter sizes (A-Z). The reference for US-system drill sizes that appear on imperial fractional and number-drill ranges.
- ISO 5418 — Tools with carbide tips: dimensions of carbide-tipped masonry drill bits. Sets the standard for TCT masonry drill geometry.
- ISO 4957 — Tool steels: covers M-series HSS designations (M2, M35, M42) and their composition tolerances.
- AS 2944 — High-speed steel twist drills — jobber series in Imperial sizes (Standards Australia — verify edition currency). Aligns with ANSI B94.11M for AU market.
- AS 1735 — Various sections cover drill-related safety standards for industrial applications.
What's NOT an AIMS drill bit standard: AS 1442 sometimes gets cited as a drill bit standard — it isn't. AS 1442 is for hot-rolled carbon steel bars (the raw material). It governs the steel feedstock, not the finished tool. Don't reference AS 1442 in drill bit purchase specifications.
For drill bit dimensional reference (metric mm, imperial fractional inches, number drill sizes #1-#80, letter drill sizes A-Z), the Metric to Imperial Conversion Chart includes the full cross-reference. For workpiece material standards (SAE/AISI/DIN/JIS/AS/NZS equivalents), see the Workpiece Material Cross-Reference Chart.
Drill Bit Selection — Frequently Asked Questions
What's the difference between HSS and cobalt drill bits?
HSS (high-speed steel) is the baseline drill material — suitable for mild steel, aluminium, brass and timber at moderate speeds. Cobalt HSS (HSS-Co) adds 5-8% cobalt to the alloy, which lets the bit retain hardness at much higher cutting temperatures. HSS-Co is mandatory for stainless steel (304 and 316), tougher alloy steels and any drilling job above mild-steel difficulty. Cobalt drills typically cost 50-100% more than plain HSS but cut stainless reliably where HSS would glaze and fail almost immediately.
Do I need a solid carbide drill bit?
Solid carbide drills make sense in three scenarios: (1) drilling hardened steel above 40 HRC, (2) production volume drilling where you need 500+ holes per bit, or (3) high-speed CNC and dry/MQL machining. For handheld drilling, low-volume jobs, or general workshop use, HSS or HSS-Co is the right choice. Solid carbide is brittle and demands a rigid machine setup (CNC, mag drill or sturdy pillar drill).
What drill bit do I use on stainless steel?
Use HSS-Co (cobalt HSS) — not plain HSS. Stainless work-hardens the moment the drill slows or chatters, and plain HSS doesn't have the hot hardness to survive. A 135° split-point HSS-Co bit (M35 or M42 cobalt content) is the right tool. Run at moderate RPM, use steady pressure (don't let the drill spin without cutting), and use cutting fluid. For 304 stainless, M35 (5% cobalt) is usually adequate; for 316 stainless or production runs, step up to M42 (8% cobalt).
What's the right drill bit for ceramic tile or porcelain?
Standard twist drills don't work on glazed ceramic or porcelain — the bit skates across the surface and may shatter the tile. Use a diamond-coated drill bit (best, especially for porcelain) or a spear-point carbide drill bit (lower cost, suitable for softer tile and glass). Both require water cooling. Drill at slow speed with light pressure. The Bordo Tile and Bordo Porcelain ranges are the AIMS-stocked specialists.
Can I use a masonry drill bit on steel?
No. Masonry drill bits have a brazed carbide tip designed for impact-driven cutting on concrete and brick. The tip geometry is wrong for steel — it can't form chips and the bit will glaze, overheat and fail. Use the correct drill bit family for the material: HSS or HSS-Co for steel, carbide-tipped masonry for concrete/brick.
What's the difference between SDS-Plus and SDS-Max?
SDS-Plus and SDS-Max are specialised shank systems for rotary hammer drills. SDS-Plus shanks are smaller (10mm), suitable for general concrete drilling up to about 32mm hole diameter, and work in standard rotary hammers. SDS-Max shanks are larger (18mm), designed for heavy concrete and rebar work above 25mm hole diameter, and require an SDS-Max-compatible hammer. They are NOT interchangeable — match the shank to the machine.
Why does my drill bit walk on the workpiece surface?
Three common causes: (1) the drill point angle is wrong (118° standard drills tend to walk on smooth surfaces — switch to a 135° split-point), (2) the workpiece needs a centre punch or spot drill mark first, or (3) the drill is dull and skating instead of cutting. For positioning accuracy on hard or smooth surfaces, use a centre drill or spotting drill first, then the main drill.
What does TiAlN coating mean and when should I use it?
TiAlN (Titanium Aluminium Nitride) is a black-purple PVD coating that delivers excellent heat resistance — making it the right choice for hardened steel, stainless steel and high-temperature drilling. It's the most popular premium coating for steel and stainless work. IMPORTANT: TiAlN does NOT work on aluminium — the coating's aluminium content catalyses with aluminium in the workpiece, causing built-up edge and immediate tool failure. For aluminium, use uncoated (bright) drill bits.
What size drill bit do I need for an M8 tapping hole?
For a standard M8 x 1.25 coarse tap (the most common), drill 6.8mm. For M8 x 1.0 fine pitch, drill 7.0mm. Don't confuse the M-designation with the drill size — M8 means a thread with 8mm nominal outside diameter, but the hole you drill is smaller (the tap drill size). Use the drill bit size chart for complete tap drill sizes across all metric and imperial threads.
What's a step drill used for?
Step drills are designed for thin sheet metal — they cut variable hole sizes in a single bit and self-deburr the hole on the up-stroke. A typical step drill might produce holes from 4mm to 12mm in 1mm increments. Use them for sheet metal cabinet work, electrical box knockouts, automotive panel work and any application needing variable hole sizes in material under 6mm thick. Don't use them for deep holes or hard materials — they're sheet-metal specialists.
How long does a drill bit last?
Tool life depends heavily on material, RPM, feed, lubrication and bit quality. A reasonable rule of thumb on suitable material: HSS jobber drill = 50-150 holes in mild steel; HSS-Co = 80-300 holes in stainless; solid carbide TiAlN = 3,000-10,000 holes in stainless at production speeds. Wrong drill choice (HSS in stainless) can collapse life to under 10 holes.
Can a drill bit be sharpened?
HSS and HSS-Co drill bits can be re-sharpened by hand on a bench grinder (skill required) or on a dedicated drill bit grinder (which holds geometry consistently). Most workshop users replace drills rather than sharpen them — the time to re-sharpen often costs more than the drill, particularly for sub-10mm sizes. Solid carbide drills are not user-sharpenable; they're regrinable at a specialist tooling regrinder for production users where the savings justify the freight and turnaround.
What drill point angle should I use?
118° standard is the default for mild steel, aluminium, brass and general workshop use. 135° split point is the right choice for stainless steel, harder alloys and hand-held drilling — the split point self-centres and prevents wandering. 140° is used on solid carbide drills for hardened steel where aggressive engagement matters more than centring. For specialty materials, the answer changes: brad point for hardwood, spear point for glass and tile, masonry geometry for concrete.
Why is my drill bit overheating?
Common causes: (1) cutting speed too high (slow the drill down), (2) feed too light (the bit is rubbing instead of cutting — push harder), (3) no lubrication (use cutting fluid for steel and stainless), (4) wrong drill material for the workpiece (HSS in stainless will overheat almost immediately — switch to cobalt). Overheating destroys the cutting edge fast — pull the drill, let it cool, and address the root cause before continuing.
What drill bit should be in my general workshop set?
For a balanced general workshop kit: HSS jobber set (1-13mm metric, fractional imperial if you work with imperial fasteners), HSS-Co set (smaller increments in mild-steel sizes for when stainless or alloy steel comes up), masonry drill set (5-13mm) for the occasional plug or anchor, a hole saw set for sheet stock cuts. For trade work add: step drill bit in HSS-Co, SDS-Plus masonry drills if you have a rotary hammer, multi-purpose drills for site work.
Related AIMS Industrial Reference Material
For deeper coverage of the engineering concepts behind drill bit selection, the AIMS Phase 4 master references include:
- Workpiece Material Cross-Reference Chart — SAE/AISI/DIN/JIS/AS/NZS equivalents across 20 material groups
- Cutting Speeds & Feeds Reference — RPM, feed rate and cutting parameter tables for drilling, milling, tapping and reaming
- Cutting Tool Materials Guide — deep coverage of HSS, HSS-Co, PM-HSS, solid carbide, PCBN and PCD
- Cutting Tool Coatings Guide — all 13 PVD coatings explained with application matrix
- Cutting Tool Troubleshooting Guide — 33 cutting symptoms diagnosed across drills, taps, endmills, reamers and bandsaw blades
- Metric to Imperial Conversion Chart — mm, decimal inch, fractional inch, drill # and gauge cross-reference
- Drill Bit Size Chart — the existing detailed size reference
- Cobalt Drill Bit Guide — M35 vs M42 stainless steel deep-dive
- Carbide vs HSS — the cost-vs-life economics
- Step Drill Bit Guide
- Hole Saw Guide
- Spot Weld Drill Bit Guide
- Tap Types Explained
- Cutting Fluids & Cutting Oils Guide
- Morse Taper Guide
- Hardness Testing Guide
For drill bit purchasing advice or to source a drill we don't currently list, ring AIMS Industrial on (02) 9773 0122 or use the contact page. Bulk pricing and trade accounts available.