Few things waste money like the wrong drill bit. A wood bit in steel burns its edge in seconds. A twist bit in hardwood leaves a ragged, oversized hole. A masonry bit run without hammer action just polishes the concrete. Sound familiar? The problem isn’t missing information — it’s that bit sets are sold on piece-count (“170-piece set!”) when what actually decides the result is geometry and bit material. This guide explains how drill bits really differ, with a material-by-material selection chart you can keep at the bench.
Anatomy of a Drill Bit
Every twist-style bit is built from the same parts, and knowing them answers nearly every “which bit?” question below:
- Point: The tip that starts the cut. A wider, flatter 135° point bites better in hard metals; the sharper 118° point is the general-purpose standard.
- Cutting lips: The two edges that do the actual shearing. They have to be symmetrical — a bit that’s sharpened lopsided drills an oversize, wandering hole.
- Flutes: The spiral grooves that carry chips up and out of the hole. Fast, open spirals for soft stuff like wood and aluminum; tighter spirals for steel.
- Shank: The part the chuck grips. Round fits any chuck, hex clicks into quick-change drivers, SDS goes in rotary hammers — and only there.
Match the point, lip geometry, and bit material to the work, and you stop burning bits.
Bit Materials: HSS vs. Cobalt vs. Carbide
What a bit is made of decides what it can cut before heat kills its edge. That’s the whole game:
| Bit material | What it is | Cuts well | Limitations |
|---|---|---|---|
| High-speed steel (HSS) | Tough tool steel that stays hard at high temperature | Wood, plastic, mild steel, aluminum | Struggles with hardened steel and stainless |
| Cobalt (HSS-Co) | HSS alloyed with cobalt — handles much more heat | Stainless steel, hard alloys, tough metals | More brittle, so no side-loading; costs more |
| Titanium-coated (TiN) | HSS with a hard gold-colored coating | Same jobs as HSS, with longer edge life | Sharpening wears the coating off — the core is still plain HSS |
| Carbide-tipped | Brazed carbide cutting edges | Masonry, concrete, tile, very hard materials | Brittle; made for rotary and hammer use, not for flexing or prying |
| Carbon steel | Basic, soft steel | Wood only | Goes dull fast in metal; the cheapest option |
Simple version: HSS is the default for general work. Reach for cobalt when stainless or hardened steel is a regular part of your week. Carbide belongs in masonry and tile bits. A titanium coating buys you more life between sharpenings — it doesn’t turn an HSS bit into a cobalt bit, no matter what the packaging implies.
The Main Bit Types and What Each Is For
- Twist bits: The universal type — in HSS or cobalt they handle metal, wood, and plastic. Every workshop has a drawer of these.
- Brad-point bits: Wood bits with a sharp center spur that locates exactly where you put it and scores the fibers for a clean entry hole. Night and day better than twist bits in wood.
- Spade (paddle) bits: Flat wood bits for fast, rough large holes (1/2″–1-1/2″) in framing and studs. Quick but crude — not for finished work.
- Forstner bits: For flat-bottomed, clean large holes — hinge cups, dowel seats. Really want a drill press or a very steady hand.
- Hole saws: Cylindrical saws for big holes in wood, plastic, drywall, and thin metal (bi-metal versions for metal). Need an arbor and a pilot bit.
- Step (unibit) bits: Cone-shaped bits that drill multiple hole sizes in sheet metal and thin stock. One step bit can replace a whole index for panel work.
- Masonry bits: Carbide-tipped, for brick, block, and concrete. Designed to run with hammer action.
- Tile/glass bits: Spear-point carbide or diamond-coated bits for hard, brittle material. Low speed and water cooling, always.
- Countersink bits: Cut the conical seat so a screw head sits flush.
- Auger bits: Deep screw-tip wood bits for thick timbers — the screw tip pulls the bit through, so you barely push.
Material-by-Material Selection Chart
This is the chart worth bookmarking. “First choice” is what a professional reaches for; the alternatives get you through in a pinch.
| Material | First choice | Also works | Notes |
|---|---|---|---|
| Softwood (pine, framing) | Brad-point or spade bit | Twist bit | Brad-point for clean holes; spade for speed |
| Hardwood (oak, maple) | Brad-point or Forstner | Twist bit | Drill slower, clear chips often, or you’ll burn the wood |
| Plywood / MDF | Brad-point | Twist bit | Back the exit side with scrap to stop blowout |
| Thin sheet metal | Step bit | Twist bit (HSS) | Clamp the sheet flat — a step bit grabs far less than a big twist bit |
| Mild steel | HSS twist bit (135° split point) | Cobalt | Cutting oil, moderate speed, firm pressure |
| Stainless steel | Cobalt twist bit | — | Slow speed, firm pressure, cutting oil — non-negotiable |
| Aluminum | HSS twist bit | Step bit for sheet | Faster speeds are fine; clear chips often — aluminum galls and sticks |
| Plastic / acrylic | Twist bit (modified low rake) or brad-point | HSS twist | Low speed, and a backing board keeps the exit from cracking |
| Ceramic tile | Diamond or carbide spear-point | — | Low speed, water cooling, and never hammer action |
| Glass | Diamond-coated bit | Carbide spear-point | Very low speed, constant water, light pressure |
| Brick / block | Carbide masonry bit | — | Hammer action on; soft brick is the one exception — rotary only |
| Concrete | Carbide masonry bit (SDS in a rotary hammer) | — | Hammer action is essential; withdraw the bit now and then to clear dust |
Speeds and Feeds: The Rule of Thumb
Ask any shop what kills the most bits and the answer is almost always speed. The rule: harder material = slower speed + more pressure; softer material = faster speed + lighter pressure. A 1/4″ bit in mild steel wants roughly a third of the RPM it would run in pine. Smaller bits tolerate higher RPM than big ones in the same material.
Two habits that stretch bit life more than anything else:
- Cutting oil on metal. It cools the edge and stops stainless from work-hardening. Even a drop of general-purpose oil beats nothing.
- Peck the hole. Drill a little, pull out to clear the chips, go again. Packed chips overheat the bit — and in small bits, they snap it.
One more for larger holes in metal: drill a pilot hole first. A small pilot (1/8″–1/4″) centers the big bit, takes load off, and keeps the hole true. Anything above about 1/2″ diameter in steel goes much easier with this step.
Sharpening and Care
A dull bit isn’t a dead bit. Twist bits can be resharpened many times on a bench grinder or with a dedicated sharpener — keep both lips symmetrical and hold the original point angle. Practice on cheap bits before you touch your cobalt set. Brad-point and Forstner bits are hard to sharpen by hand, so most shops just replace them; spade bits take a file fine.
Bits rattling loose in a drawer chip each other’s cutting edges — and you won’t notice until the holes go bad. Keep them in an index or a case. And never run a bent bit: it drills oversize holes and it’s a breakage waiting to happen.
Buying Bits: Sets vs. Individual, and Bulk Strategy
- For general use, a quality HSS set covering 1/16″–1/2″ plus a small masonry set handles the vast majority of jobs. Skip the giant piece-count sets — they’re padded with odd sizes you’ll never reach for.
- Buy the sizes you burn through as individuals. Every shop has its “consumable” sizes — often 1/8″, 3/16″, and 1/4″ in metal work. Those deserve multipacks, not whatever came in the set.
- For workshops buying in bulk, standardize first: one shank system, fixed sizes per workstation, and track which sizes disappear fastest — those are the ones to price-shop in quantity. Price factors are bit material (cobalt runs notably more than HSS), coating, and grinding precision. And the hidden cost: a cheap bit snapping off inside a workpiece costs more in labor than it ever saved. EquipFuture supplies drill bits in bulk with a 100-unit minimum order, so standardizing your consumable sizes before you order keeps things simple.
- Masonry bits are consumables in concrete work. Budget them per project, not per year.
Common Mistakes to Avoid
- Running a wood bit in metal — or expecting a twist bit to leave a clean hole in wood. Wrong geometry, wrong result.
- High speed in steel. The classic way to blue a bit and kill it in seconds.
- No cutting oil on metal, especially stainless. The edge cooks, the steel work-hardens, and everything gets worse from there.
- Hammer action on tile. Cracks it on the spot.
- Forcing a dull bit instead of sharpening or replacing it. It work-hardens the material and makes the next attempt harder too.
- Buying on piece-count instead of bit material and geometry.
- Side-loading bits — using the drill like a router. Snaps bits, and with larger diameters it’s genuinely dangerous.
FAQs
1. What’s the difference between HSS and cobalt bits?
Cobalt bits are HSS alloyed with cobalt, so the cutting edge survives higher temperatures. In practice: HSS for general metal and wood; cobalt when you regularly drill stainless or hardened alloys. Harder but more brittle — no bending or side-loading.
2. Can I sharpen drill bits myself?
Yes — standard twist bits resharpen well on a bench grinder or with a drill-bit sharpener. The hard part is keeping both cutting lips symmetrical and holding the original point angle. Practice on cheap bits first.
3. Why do my bits keep breaking in metal?
Usually it’s one of four things: too much speed, too little pressure (so the bit rubs instead of cutting), no cutting oil, or a dull bit being forced. Fix the technique before you blame the bit.
4. Do I need a hammer drill for masonry bits?
A hammer drill with carbide masonry bits handles brick and block. For solid concrete, a rotary hammer with SDS bits is dramatically faster — it’s a different mechanism, not just more power.
5. What does “split point” mean?
A split point is a self-centering tip grind that starts exactly where you place it — no center punch, no “walking.” It’s standard on quality HSS bits and worth seeking out.
6. Are titanium-coated bits better than plain HSS?
The coating is harder than the base steel, so they last longer between sharpenings — but sharpen through it and you’re back to plain HSS. Treat the coating as extended life, not a different capability.
Conclusion
Drill bits reward understanding over spending. A modest kit of the right bits — HSS twist bits for general work, cobalt for hard metals, brad-points for wood, carbide masonry bits for concrete — picked from the material chart above and run at sensible speeds with cutting oil, will beat a drawer of mismatched bargain bits every time. For workshops, the play is standardization: stock the sizes your work actually consumes, buy those in bulk, sharpen what’s worth sharpening, and replace the rest. The hole is only as good as the bit you chose before you pulled the trigger.