Choosing the right drill bit saves money, time and broken tools. The three grades you will meet most often are HSS (high-speed steel), cobalt HSS (often marked HSS-Co or M35) and solid carbide. Each one suits different materials and machines.
Quick answer: which drill bit should I buy?
| Material you are drilling | Best choice | Why |
|---|---|---|
| Mild steel, wood, plastic, aluminium | Standard HSS | Tough, affordable and easy to resharpen |
| Stainless steel, alloy steel, cast iron | Cobalt HSS (M35) | Keeps its hardness at higher heat |
| Hardened steel, high-volume CNC work | Solid carbide | Very hard and fast, needs a rigid machine |
| Concrete, brick, stone | SDS Plus masonry bit | Made for hammer drilling |
HSS drill bits: the everyday workhorse
High-speed steel bits are the standard choice for workshops, maintenance teams and fabricators. They handle mild steel, non-ferrous metals, wood and plastic, and they forgive the small wobbles of a hand drill. A black oxide finish helps resist rust and holds cutting oil on the surface.
- Best for general drilling in a hand drill or drill press
- Can be resharpened many times
- Available in metric (MM) and inch sizes, singly or in sets
Browse our HSS drill bits in metric and inch sizes.
Cobalt (M35) drill bits: for stainless steel and tough alloys
Cobalt drill bits are HSS with about 5% cobalt added. The cobalt helps the cutting edge stay hard when it gets hot, which is exactly what happens when you drill stainless steel. They cost more than standard HSS, but on hard or work-hardening metals they last much longer.
Tip: stainless steel hardens if the bit rubs instead of cuts. Use a lower speed, firm steady pressure and plenty of cutting oil.
Solid carbide drill bits: speed and precision on machines
Carbide is much harder than HSS and can run at higher cutting speeds, which makes it the choice for CNC machining centres and production work. The trade-off is that carbide is brittle. It needs a rigid set-up and good coolant, and it can chip or snap in a hand drill.
See our carbide drill bits and endmills.
How to make any drill bit last longer
- Match the speed to the size. Larger diameters need lower speeds.
- Use cutting oil on steel. It reduces heat and gives a cleaner hole.
- Centre punch first. A small dent stops the bit from wandering.
- Drill a pilot hole for holes larger than about 10 mm.
- Clear the chips on deep holes by pulling the bit out every few millimetres.
Still not sure?
Tell us the material, hole size and machine you are using and our team will recommend the right bit. Contact us or send a quote request with your quantities.
