How to Choose the Right Drill Bits

Drill bits are easy to ignore until a job goes wrong. You clamp in whatever's nearest, lean on the drill, and wonder why the hole is ragged, the bit is smoking, or the tip has skated across the tile and left a scar. Nearly always, the problem isn't the drill or your technique; it's the wrong bit for the material in front of you.

Choosing well isn't complicated once you know what to look for. There are only a handful of bit types you'll ever need at home, each built for a particular surface, and telling them apart takes a minute. Get the match right and drilling becomes quick, clean, and notably safer, because a bit that cuts as intended doesn't grab, wander, or overheat.

Match the bit to the material#

The single most important choice is pairing the bit to what you're drilling into. Use the wrong one and, at best, you ruin the hole; at worst, the bit binds and the drill twists in your hands.

• Wood bits have a small point in the centre that stops them wandering and helps bore clean holes in timber and boards.
• Metal bits, usually high-speed steel, are ground to cut through steel, aluminium, and plastic, and they also work fine in wood.
• Masonry bits have a tougher tip and are made for brick, concrete, and stone, ideally used with a hammer drill setting.
• Tile and glass bits have a spear-shaped tip designed to score hard, brittle surfaces without cracking them.
• Spade or auger bits bore the large-diameter holes you need for pipes and cables through timber.

If you remember only one thing, let it be this: a masonry bit will make a rough mess of metal, and a wood bit will burn itself out on brick. When in doubt, identify the surface first, then pick the bit.

A couple of specialist shapes earn their place once you've got the basics. A countersink bit cuts a shallow, cone-shaped recess so a screw head sits flush with, or just below, the surface, which looks tidier and stops the head snagging. A brad-point bit is a wood bit with a sharper centre spur for extra-clean, precisely placed holes, handy for furniture and joinery. Neither is essential on day one, but both are cheap and genuinely useful when a job asks for a neater result.

Read the sizes without the guesswork#

Bit sizes come in millimetres or fractions of an inch, and the number is simply the diameter of the hole the bit will cut. For screws, a good habit is to drill a pilot hole slightly narrower than the screw's solid core, so the threads still bite while the wood doesn't split. For wall plugs, match the bit to the plug size printed on the packet rather than eyeballing it.

A bit gauge, that little metal plate with graduated holes, takes the mystery out of an unlabelled bit: drop the bit through until it fits snugly and read off the size. It's a cheap thing to own and it saves a lot of squinting at worn markings.

Drilling a hole slightly too small and enlarging it is easy; a hole drilled too big can't be undone. When you're unsure, start under and step up. Patience costs a few seconds, while an oversized hole can cost you the whole piece.

Understand coatings and materials#

Beyond the shape, bits differ in what they're made of and how they're finished, and it does affect how they perform. Basic high-speed steel bits are perfectly good for wood and light metal work. A titanium coating adds hardness and helps the bit last longer, which is handy if you drill metal often. Cobalt bits handle tougher, harder metals and stay sharp under heat, though they're overkill for most home jobs.

For a first kit, you don't need the exotic stuff. A decent mixed set of wood and metal bits, plus a few masonry bits in common wall-plug sizes, covers the vast majority of household drilling. You can always add specialist bits when a specific job calls for one, which is exactly the buy-as-you-need approach we recommend in our guide to building your first home tool kit.

Keep bits sharp, and treat dullness as a hazard#

A sharp bit cuts with light pressure and stays cool. A dull one makes you push harder, which builds heat, and heat is where things go wrong: the bit can seize, the workpiece can crack, and the drill can twist unexpectedly in your grip. Treating a blunt bit as merely annoying misses the point, because it's genuinely less safe to use.

You can spot a tired bit easily. Look for a rounded or chipped cutting edge, blue or scorched discolouration near the tip from overheating, or a bit that skates instead of biting. Some bits can be resharpened, but the small ones are cheap enough that replacing them is usually the sensible call. Whatever you do, don't force a dull bit through the job; swap it and carry on cleanly.

Drill cleanly and cool#

Even the perfect bit needs a little technique to do its best work. Let the bit reach speed before it touches the surface, keep the drill square to the work, and apply steady, moderate pressure rather than leaning your weight on it. For deeper holes, pull the bit out every few seconds to clear the waste and let it cool, especially in metal.

When drilling metal, a drop of oil on the spot reduces heat and helps the bit cut, extending its life noticeably. On tile, start slow with the tip angled slightly to score a starting point, then bring the drill upright and ease off the pressure. All of this pairs naturally with sound tool habits generally, which our guide to using a cordless drill safely lays out in full.

Clamping matters more than people expect here as well. A workpiece that's held firmly can't spin if the bit grabs, which is exactly the moment a loose board becomes a spinning hazard. Small metal offcuts are the worst offenders, since they can whip round faster than you'd believe, so clamp them down every time rather than pinning them with a finger. A little heat is normal, but if the bit or the metal becomes too hot to touch, stop and let both cool before carrying on.

Putting it all together at the shop#

Next time you're choosing bits, skip the giant hundred-piece case that's mostly sizes you'll never touch. A quality mixed set of wood and metal bits, a small handful of masonry bits matched to the wall plugs you actually use, and a tile bit if your bathroom project calls for one, will serve you for years.

Store them somewhere they won't rattle loose and chip their tips, keep an eye on their condition, and retire the dull ones without sentiment. Do that and the humblest, cheapest part of your kit will quietly make every hole you drill cleaner, faster, and safer than the last.