Using the wrong drill bit is like using a butter knife as a screwdriver — it sort of works, but poorly, slowly, and with a high chance of damaging the bit, the material, or both. The right drill bit for the job cuts cleanly, lasts longer, and makes the work easier. But with dozens of bit types, materials, coatings, and sizes available, choosing the right one can be confusing. This guide matches bit types to materials so you always grab the right bit for the job.
Drill Bit Anatomy
Every drill bit has three functional parts: the tip (the cutting geometry that determines how the bit enters the material), the flutes (the spiral grooves that evacuate chips and debris from the hole), and the shank (the smooth section that the drill chuck grips). The tip geometry is the most important factor in matching a bit to a material.
Bits for Wood
Brad Point Bits
The best general-purpose wood bit. The center point (brad) positions the hole precisely, and the outer spurs score the wood fibers before the cutting edges engage — producing clean, splinter-free holes. Available in sizes from 1/8 inch to 1/2 inch. Use for: furniture building, cabinetry, dowel holes, and any application where hole quality matters. Not suitable for metal or masonry.
Spade (Paddle) Bits
A flat, paddle-shaped bit that cuts large holes (3/8 inch to 1-1/2 inch) quickly in wood. The center point positions the hole, and the flat cutting edges remove material aggressively. Produces rougher holes than brad point or Forstner bits — suitable for rough carpentry (running wires, plumbing holes) but not for visible surfaces. Inexpensive ($5-$15 for a set).
Forstner Bits
The premium wood bit for clean, flat-bottomed holes. The circular rim scores the wood fibers while the center cutting edges remove material, producing the cleanest holes of any wood bit. Available in sizes from 1/4 inch to 2+ inches. Use for: hinge mortises, counterbores, overlapping holes, and any application requiring a flat-bottomed or clean-edged hole. Best used in a drill press for precision. More expensive ($20-$50 for a set).
Auger Bits
Deep-hole bits with aggressive spiral flutes that pull chips out of deep holes efficiently. The threaded tip pulls the bit into the wood without requiring downward pressure. Available in lengths up to 18 inches. Use for: drilling through thick timbers, log construction, and any hole deeper than 3 inches. The self-feeding action can be aggressive — use in a drill with a side handle for control.
Hole Saws
A cylindrical saw blade that cuts large-diameter holes (3/4 inch to 6+ inches) in wood, plastic, and thin metal. The center pilot bit positions the hole, and the toothed cylinder cuts the perimeter. Use for: doorknob holes, pipe penetrations, and any large-diameter through-hole. Available in individual sizes or adjustable sets.
Bits for Metal
HSS (High-Speed Steel) Twist Bits
The standard metal-drilling bit. The 118° or 135° split-point tip cuts into metal without walking (sliding across the surface). HSS withstands the heat generated by metal drilling. Available in sizes from 1/16 inch to 1/2 inch. Use for: mild steel, aluminum, copper, brass, and most non-ferrous metals. The most versatile and affordable metal bit ($10-$25 for a set).
Cobalt Bits (HSS-Co)
HSS with 5-8% cobalt added for increased heat resistance and hardness. Cobalt bits maintain their cutting edge at higher temperatures, making them essential for drilling hard metals — stainless steel, cast iron, and hardened steel. More expensive than standard HSS ($20-$50 for a set) but last significantly longer in hard metals. Use for: stainless steel, cast iron, and any metal that dulls standard HSS bits quickly.
Titanium-Coated Bits
Standard HSS bits with a titanium nitride (TiN) coating that reduces friction and increases surface hardness. The gold-colored coating extends bit life by 2-3x in mild steel and aluminum. The coating wears off with sharpening, so once the coating is gone, they perform like standard HSS. Use for: general metal drilling where extended bit life is desired. Not a substitute for cobalt bits in hard metals.
Step Bits (Unibit)
A cone-shaped bit with stepped diameters that drills multiple hole sizes with a single bit. Excellent for drilling clean holes in sheet metal (up to 1/8 inch thick) without the grabbing and deformation that twist bits cause in thin material. Available in sizes from 1/8 inch to 1-3/8 inch. Use for: electrical boxes, sheet metal, and any thin material where a clean, burr-free hole is needed.
Bits for Masonry
Carbide-Tipped Masonry Bits
The standard bit for concrete, brick, block, and stone. The carbide tip (brazed onto an HSS body) withstands the abrasion of masonry materials. Use with a hammer drill in hammer mode — the hammering action pulverizes the masonry while the rotation clears debris. Standard masonry bits have a straight shank for 3-jaw chucks. SDS-Plus bits have a slotted shank for SDS hammer drills (more efficient power transfer). Use for: anchor holes in concrete, mounting brackets on brick, and any hole in masonry material.
Bits for Tile and Glass
Carbide-Tipped Tile Bits
A spear-shaped carbide tip that cuts through ceramic and porcelain tile without cracking. Use at low speed (under 1,000 RPM) with water cooling (a wet sponge held against the drilling point). No hammer action — tile bits rely on abrasion, not impact. Start the hole at an angle to prevent the bit from walking on the smooth tile surface, then straighten to 90° once the hole is started.
Diamond-Coated Bits
For glass, porcelain, marble, and granite — materials too hard for carbide. The diamond coating abrades through the material at low speed with water cooling. Expensive ($10-$30 per bit) but the only option for hard, brittle materials. Use a drill press or guide for precision — these bits walk easily on smooth surfaces.
Bit Maintenance
A dull bit generates heat, produces rough holes, and requires excessive pressure — all of which damage the bit, the material, and potentially the drill. HSS and cobalt bits can be sharpened with a bench grinder or a dedicated drill bit sharpener ($30-$60). Carbide-tipped bits require diamond sharpening tools. Brad point and Forstner bits are best sharpened by hand with a fine file or sent to a professional sharpening service.
Store bits in a case or organizer — loose bits in a drawer bang against each other and dull the cutting edges. Keep bits dry to prevent rust on HSS bodies.
Quick Reference: Which Bit for Which Material
Softwood: Brad point or twist bit. Hardwood: Brad point or Forstner. Plywood/MDF: Brad point (reduces tear-out). Mild steel: HSS twist bit. Stainless steel: Cobalt bit. Aluminum: HSS or titanium-coated. Sheet metal: Step bit. Concrete/brick: Carbide masonry bit with hammer drill. Ceramic tile: Carbide tile bit, low speed, water cooling. Glass/porcelain: Diamond bit, low speed, water cooling. Plastic: HSS twist bit at low speed (high speed melts plastic).
When in doubt, start with a small pilot hole and work up to the final size. A pilot hole reduces the force required, improves accuracy, and reduces the risk of material damage — especially in hard metals and brittle materials.