Drill Bits Explained: Types, Materials and When to Use Each

Walk into any hardware aisle and the types of drill bits on the wall can look like alphabet soup: twist, brad point, spade, Forstner, step, masonry, auger — and that is before you get to the coatings. Most people grab whatever is cheapest, burn through it in a week, and conclude that drill bits are disposable. They are not, if you match the bit to the material.

This guide covers every common type of drill bit, what each one is actually for, and the materials and coatings that separate a bit that lasts from one that dies on the third hole. By the end you will know exactly which bit to reach for, whether you are hanging a shelf, drilling steel plate or boring clean holes for dowels.

Drill Bit Anatomy in 60 Seconds

Every drill bit has the same basic parts. The point is the cutting tip — its angle and shape decide how the bit starts and what it cuts. The flutes are the spiral grooves that carry chips up and out of the hole. The shank is the part the chuck grips. Knowing these three terms makes everything below much easier to follow, because most bit types are just variations on point shape and flute design optimised for a specific material.

The Main Types of Drill Bits

Twist bits: the everyday workhorse

The twist bit is the classic spiral bit that comes in every drill set, and it handles the widest range of jobs: wood, plastic, and light metal. Standard twist bits have a 118-degree point that works well in wood and soft metals; bits with a 135-degree split point self-centre on metal and resist walking. If you buy one set, make it a good high-speed steel twist set in the sizes you actually use — 1/16 inch up to 1/2 inch covers most household work.

Brad point bits: clean holes in wood

Brad point bits have a sharp centre spur and two cutting spurs on the edges. The centre point bites in exactly where you place it, so the bit does not wander, and the outer spurs score the wood fibres before the main cutting edges remove them. The result is a clean entry hole with no tear-out — the reason woodworkers reach for brad points for visible holes in furniture and cabinetry. They are for wood only; the spurs dull fast in metal.

Spade (paddle) bits: fast, rough holes in wood

Spade bits are flat paddles with a pointed tip and two cutting wings. They drill large-diameter holes in wood very quickly and cost almost nothing, which makes them perfect for rough work like running cables through studs. The downside is ragged holes — they tear the exit side badly. Drill from both sides or clamp a sacrificial board behind the workpiece if the exit will be visible. Bosch’s titanium-coated spade bits (16 and 22 mm in their X-Line sets) are a solid example of the type.

Forstner bits: perfect flat-bottomed holes

Forstner bits bore clean, flat-bottomed holes with crisp edges — the kind you need for concealed cabinet hinges, dowels and inlays. The rim scores the wood while the centre cutters remove material, so they cut overlapping holes and holes on edges that would defeat a spade bit. They need a drill press (or a very steady hand and low speed) to work safely, because they grab aggressively. For more on the tool that runs them best, see our drill press buying guide.

Hole saws: big diameters in wood, drywall and thin metal

A hole saw is a cup-shaped saw with teeth on the rim and a pilot bit in the centre. It cuts holes from about 3/4 inch up to 6 inches — door locksets, recessed lights, plumbing penetrations. Bi-metal hole saws handle wood, drywall, plastic and thin sheet metal. Keep the speed low, clear chips often, and let the teeth cut; pushing hard just overheats the saw and melts the teeth’s temper.

Step bits: one bit, many hole sizes in sheet material

Step bits (often called unibits) are cone-shaped with stepped diameters, letting you drill multiple hole sizes in thin sheet metal, plastic and acrylic with a single bit. Electricians love them for enlarging knockout holes in electrical boxes. They only work in thin material — do not try to step-drill thick steel plate. A drop of cutting oil makes a dramatic difference to their lifespan.

Masonry bits: for brick, concrete and stone

Masonry bits have a carbide tip brazed onto a steel body and a wider flute profile to clear dust. The carbide tip grinds through brick, block, mortar and concrete while the flutes evacuate the dust. Use them with the hammer function on a hammer drill for concrete — in rotary-only mode they will eventually get through brick but it takes forever. Bosch’s CYL-1 masonry bits are the standard example of the type. Never use a masonry bit on wood or metal; it will just skate and overheat.

Auger bits: deep holes in timber

Auger bits have a screw-like tip that pulls the bit into the wood and a single deep flute that clears chips from deep holes. They are the choice for boring deep holes in studs, joists and fence posts — anywhere a spade bit would wander or clog. The lead screw means you barely need to push; in fact, with a powerful drill you need to hold back, because an auger bit can yank the drill forward. Keep them sharp and they cut almost effortlessly.

Countersink bits: seating screw heads flush

A countersink bit cuts a conical recess so a flat-head screw sits flush with (or just below) the surface. Many woodworkers use combination drill-countersink bits that drill the pilot hole and cut the countersink in one step. For a cleaner look in fine work, follow with a plug cutter and glue in a matching wood plug to hide the screw entirely.

Glass and tile bits: spear points and diamond

Standard twist bits shatter glass and glaze. Spear-point bits (with a carbide spear tip) score and grind through glass, ceramic tile and porcelain at low speed with water as a coolant. For porcelain and stone, diamond-coated hole saws and core bits are the pro choice — they grind rather than cut, so patience and constant water cooling are mandatory. Never use the hammer function on tile.

SDS-Plus bits: for rotary hammers

SDS-Plus bits have a special slotted shank that locks into rotary hammers (not standard drill chucks). Combined with the hammer’s piston action, they drill concrete and reinforced masonry far faster than any standard masonry bit. If you are drilling more than a handful of holes in concrete — say, mounting a TV bracket on a concrete wall — renting or buying an SDS rotary hammer with proper SDS-Plus bits will save you hours.

Drill Bit Materials and Coatings Explained

The bit’s shape decides what it cuts; the material decides how long it keeps cutting. Here is the hierarchy, from basic to specialised.

High-speed steel (HSS): the standard

HSS is the baseline material for twist bits. It stays hard at the temperatures drilling generates and can be resharpened. Plain HSS bits are fine for wood, plastic and occasional light metal work. They are also the cheapest, which is why every starter set is full of them.

Black oxide: HSS with a tougher skin

Black oxide is a surface treatment on HSS that improves corrosion resistance and reduces friction slightly. Black oxide bits run a bit cooler and last longer than bright-finish HSS in metal. They are a sensible, inexpensive upgrade if you drill metal regularly but do not want to pay for coated bits.

Titanium nitride (TiN): the gold coating

Those gold-coloured bits are HSS with a thin titanium nitride coating that increases surface hardness and reduces friction, letting the bit run cooler and last longer. Bosch’s Impact Tough titanium drill bits (the TI5IM 5-piece and TI9IM 9-piece sets, covering 1/16 to 3/8 inch) are a good example: TiN coating, a no-skate split-point tip for clean starts, and an impact-rated 1/4-inch hex shank for use in impact drivers. Bosch rates them at twice the life of standard impact drill bits in metal, wood and plastic. One honest caveat: the coating is only skin-deep, so once you resharpen past it you are back to plain HSS. Read Bosch’s own Impact Tough announcement for the details of the line.

Cobalt (M35/M42): for hard and stainless steel

Cobalt bits are HSS alloyed with 5% (M35) or 8% (M42) cobalt all the way through — not a coating. That makes them genuinely harder and far more heat-resistant than TiN-coated bits, which is what you need for stainless steel, cast iron and hardened steel. They cost more and are more brittle (do not flex them sideways), but for tough metals nothing else comes close. If your TiN bits keep dying in stainless, cobalt is the answer.

Carbide: the hardest option

Carbide is the hardest common bit material, used for masonry tips and for production metal drilling. Solid carbide bits are superb but expensive and very brittle — snap one and you will feel it in your wallet. For home workshops, carbide-tipped masonry bits and the occasional carbide burr are all most people need.

Point Angles, Shanks and Sizes

Two more details that separate good results from frustration. Point angle: 118-degree points are the general-purpose standard and work well in wood and soft metals. 135-degree split points self-centre and cut more aggressively in hard metals — if you drill steel, buy 135-degree bits. Shanks: round shanks fit any chuck; 1/4-inch hex shanks lock into impact drivers and quick-change chucks without slipping; SDS-Plus shanks only fit rotary hammers. Match the shank to the tool, and when buying sets, check that the size range covers what you actually drill — a 1/16-to-1/2-inch twist set plus a small spade set handles the vast majority of home projects. Pair the right bit with the right machine: our best cordless drills guide covers drill selection.

How to Drill Without Ruining Bits

Most dead drill bits were murdered, not worn out. The killers are heat and impatience. Run metal-drilling at moderate speed with firm, steady pressure — you want a continuous curl of swarf, not dust and smoke. Use cutting oil on steel; it easily doubles bit life. Drill a pilot hole (about half the final diameter) before large holes in metal. Back the bit out periodically to clear chips, especially in deep holes. And clamp the workpiece — a spinning workpiece is how injuries happen. Clamp it, wear eye protection, and keep your hands clear, as we cover in our workshop safety guide.

Frequently Asked Questions

What is the difference between titanium and cobalt drill bits?

Titanium bits are HSS bits with a thin titanium nitride coating that reduces friction and extends life — good general-purpose bits for wood, plastic and light metal. Cobalt bits have cobalt alloyed through the entire bit, making them harder and far more heat-resistant. Choose cobalt for stainless steel, cast iron and other hard metals; choose titanium-coated for everyday work.

Can I use a wood drill bit on metal?

Brad point, spade and auger bits are designed for wood and will dull quickly or skate dangerously on metal. Use HSS twist bits (preferably 135-degree split point) for metal. The one crossover: standard twist bits work fine in wood, which is why they are the default bit in most drill kits.

Why do my drill bits keep breaking?

The usual causes are too much speed in metal (which overheats the bit), too much sideways pressure (bits are not designed to bend), drilling without cutting oil in steel, or using the wrong bit for the material. Cobalt bits in particular are hard but brittle — any side load snaps them. Slow down, use oil, clamp the work and let the bit cut.

What size drill bit should I use for a pilot hole?

For wood screws, the pilot hole should match the screw’s shank diameter (the solid core, not the threads) — roughly 70-80% of the screw’s outer diameter in softwood, a touch larger in hardwood. For large holes in metal, drill a pilot hole about half the final diameter first; it reduces the load on the big bit enormously.

Are expensive drill bit sets worth it?

Up to a point. A quality HSS or TiN-coated set from DeWalt, Bosch, Milwaukee or Makita will outlast bargain-bin bits many times over and drill straighter holes. Beyond that, buy specialised bits (cobalt, Forstner, SDS-Plus) individually for the jobs you actually do rather than paying for a 200-piece set full of sizes you will never touch.