Drill Bit Types Explained: Which Bit for Which Material

Drill Bit Types — a practical guide for Australian trades from the team at Power Tools Direct Australia.

Which bit for steel, stainless, timber, tile and masonry — plus the two speed-and-pressure rules that stop you burning bits.

Most drilling problems are bit problems

If a hole is taking too long, wandering, burning or the bit has gone blue, the tool is almost never at fault. It is the wrong bit, the wrong speed, or a blunt bit. Browse drill bits to see the options.

Bits for metal

• HSS (high speed steel) — the standard, general purpose. Fine for mild steel and aluminium.
• HSS-TiN (titanium coated) — a hard gold coating that reduces friction. Lasts longer in mild steel; the coating cannot be resharpened.
• Cobalt (HSS-Co, M35/M42) — cobalt in the alloy itself, so heat resistance runs all the way through. Essential for stainless steel.
• Carbide — for hardened steel and cast iron. Brittle; needs a rigid setup.
• Step (cone) bits — for thin sheet metal, producing clean round holes without grabbing.

Bits for timber

• Brad point — a centre spur stops wandering. The right choice for accurate holes in timber.
• Auger — a screw tip pulls the bit through. Fast, deep holes for services through joists.
• Spade (paddle) — cheap and fast, rough exit hole. Fine for holes you will cover up.
• Forstner — flat-bottomed, clean-sided holes. Essential for concealed hinges in cabinetry.
• Holesaw — large diameters in thin material. See the holesaw guide.

Bits for masonry

Masonry bits have a brazed carbide tip designed to be struck, not just rotated. Use them in hammer mode.

For anything beyond a few holes, move to SDS. Round-shank masonry bits in a keyless chuck slip under load and the chuck takes the punishment.

Speed and pressure: the two rules

1. Big bit, slow speed. A 25 mm holesaw at full speed will burn. Large diameters need low RPM.
2. Steady firm pressure. Let the bit cut. Too little pressure rubs and generates heat; too much snaps the bit.

A blue bit is a dead bit. Heat is what kills drill bits, and heat comes from too much speed and not enough pressure.

Lubrication and pilot holes

Cutting fluid on steel roughly doubles bit life and improves the hole. Even a squirt of general purpose oil helps significantly.

For holes over about 10 mm in metal, drill a pilot hole first. It removes the work the bit’s non-cutting centre would otherwise have to do.

The bottom line

Which bit for steel, stainless, timber, tile and masonry — plus the two speed-and-pressure rules that stop you burning bits. Everything we sell is genuine Australian stock with full manufacturer warranty, dispatched same day on orders placed before 1pm AEST from our Sydney warehouse. Standard delivery is $15.99, express is $32.55, and delivery is free on orders over $1,000.

Not sure which option suits your work? Talk to our team — we are tradies too. You can also browse the full power tool range, read the FAQs, or set up a trade account for ongoing pricing.

Frequently asked questions

What bit do I need for stainless steel?

Cobalt (M35 or M42), slow speed, firm pressure and cutting fluid. Standard HSS will work-harden the material and blunt immediately.

Can I use a masonry bit on tile?

For soft ceramic, sometimes. For porcelain you need a diamond tipped tile bit and water cooling.

Why does my bit wander when starting?

Use a centre punch on metal or a brad point bit in timber. Starting at low speed also helps enormously.

Keep reading

• SDS, SDS Plus and SDS Max Explained
• Hole Saws: Bi-Metal, Carbide and Diamond
• Best Cordless Drills in Australia

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