Every Common Drill Bit Type — and the Material Each One Is Actually For
A working guide to drill bit types — twist, brad point, masonry, spade, Forstner, hole saw, step — and how to match bit to material without burning either.
By Ray Kowalski · · 2 min read
Most drilling problems are matching problems. The drill was fine; the bit was wrong for the material. Here is the short version of a decade of watching bits die.
Twist bits: the default
The standard spiral bit handles wood, plastic, and — in the right steel — metal. The steel is the whole story. Plain HSS (high-speed steel) drills wood and mild steel. Cobalt (M35/M42) bits keep their temper in stainless. Titanium-coated bits are HSS with a golden paint job: the coating helps until the first sharpening removes it.
Brad point: clean holes in wood
A center spur and two cutting wings score the hole’s rim before the body arrives, so the hole doesn’t wander and doesn’t splinter. For furniture and dowel joints, nothing else is worth using.
Masonry bits: for the hammer
A carbide tip brazed into a soft steel body, made to be hammered. In brick, block, and concrete, use them in a drill’s hammer mode — or better, an SDS rotary hammer, which drills in seconds what a hammer drill grinds at for a minute.
Spade and auger: fast, ugly, deep
Spade (paddle) bits tear fast, rough holes for wiring and plumbing. Augers pull themselves through thick timber and eject chips as they go. Neither leaves a hole you’d want visible.
Forstner: flat-bottomed and precise
Forstner bits cut clean, flat-bottomed holes and overlapping holes — the cabinet hinge bit. They need a drill press or a steady hand at low speed; they’re rim-guided, not point-guided.
Hole saws and step bits
A hole saw cuts big diameters (doorknobs, downlights) by removing a ring instead of the whole volume. A step bit drills sheet metal in graduated diameters and deburrs its own hole — the electrician’s favorite.
The three habits that outlast any bit
- Slow down in metal. Big bit, slow speed, firm feed, a drop of oil. Smoke means the temper is leaving the steel.
- Peck in deep holes. Retract to clear chips; packed flutes snap bits.
- Buy the material, not the count. A 21-piece cobalt index beats a 170-piece mystery-steel set that dulls on the second joist.