Most drilling problems come down to using the wrong bit. A bit made for wood will go blunt in brick within seconds, and a masonry bit will tear a ragged hole in timber. The good news is that you only need to recognise three main types.
Wood bits
How to spot one: a sharp point in the centre of the tip, with two small spurs either side.
The point stops the bit wandering and the spurs cut a clean edge. Use normal drill mode (no hammer) at a medium to high speed. To avoid splintering on the far side, clamp a scrap piece of wood behind your work or stop when the point pokes through and finish from the other side.
For bigger holes in wood, use a flat bit (also called a spade bit) or, larger still, a holesaw.
Masonry bits
How to spot one: a wider, arrow-shaped tip that looks like it's been added on to the end.
That tip is a hard insert made for brick, block, stone and concrete. Use hammer mode if your drill has it, and pull the bit out every few seconds to clear the dust. Never use hammer mode on tiles: start slowly without it until you're through the glaze.
Metal bits (HSS)
How to spot one: a plain, angled tip with no point or insert. Titanium-coated ones are gold in colour.
Use a slow speed and steady pressure. Mark the spot with a centre punch first so the bit doesn't skid, and add a drop of oil to keep it cool. For holes over about 6 mm, drill a small pilot hole first. HSS bits also work in wood and plastic if that's all you have to hand.
Which size?
- Wall plugs: match the bit to the plug. The size is usually printed on the pack: a 6 mm masonry bit for a 6 mm plug.
- Pilot holes in wood: choose a bit slightly thinner than the solid core of the screw, so the threads still bite.
- Not sure? Start smaller. You can always make a hole bigger.
One set that covers all three
A mixed set saves buying bits one at a time. The Bosch X-Line 70-piece set has metal, masonry and wood drill bits plus screwdriver bits, sockets and a tape measure. The Bosch 103-piece accessory set adds four holesaws and nut setters for bigger jobs.
This guide is general information. Always read and follow the instructions that come with your tool, and wear suitable eye protection.
