Best Drill Bits for Metal (2026): Cobalt, HSS & Step Bits
For general steel and stainless work on a drill press, a 135-degree split-point cobalt (M35/M42) bit set is the practical default — cobalt tolerates the heat of drilling stainless and hardened steel that burns up standard high-speed steel (HSS) in a fraction of the holes. Match bit material to workpiece hardness first, then size and coating; skipping that step is why bits dull on the first hole.
This guide covers bits for the machines in the drill presses for metal and magnetic drill press guides. Fit claims use manufacturer data; duty-cycle claims are conditional on coolant use, feed rate, and workpiece hardness.
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Compatibility table: what fits which metal-drilling job?
| Product | Fits | Size/Thread | Price |
|---|---|---|---|
| M35 cobalt bit set (135° split point) | Mild steel, stainless, cast iron on drill presses and mag drills | 1/16-1/2 in, 3/8 in round shank | $30-$60 for 13-29 piece set |
| M42 cobalt bit set (8% cobalt) | Hardened steel, stainless, high-nickel alloys under sustained duty | 1/16-1/2 in, 3/8 in round shank | $45-$90 for 13-29 piece set |
| Black-oxide HSS bit set | Mild steel, aluminum, occasional-use light fabrication | 1/16-3/8 in, 3/8 in round shank | $15-$30 for 21-29 piece set |
| Titanium-coated HSS bit set | Mild steel, sheet metal, wood; not for hardened or stainless steel | 1/16-3/8 in, 3/8 in round shank | $15-$25 for 13-21 piece set |
| Step drill bit (unibit), 3-8 or 4-40 range | Sheet metal and thin-wall tube up to roughly 1/8-3/16 in, on drill presses and handheld drills | 1/8-1/2 in or 3/16-7/8 in step range, 3/8 in shank | $12-$25 per bit |
The table is a starting point, not a substitute for matching bit material to the specific alloy being drilled. A “cobalt” bit still needs correct speed and feed to avoid work-hardening stainless.
Top drill bits for metal work
M35 cobalt bit set: the general-purpose metal default
An M35 cobalt (5% cobalt content) set with a 135-degree split point is the reasonable starting purchase for a shop drilling mixed mild steel, stainless, and cast iron. Per manufacturer data, the split point reduces walking on contact and starts cutting immediately rather than skating across the surface, which matters most on a drill press where the operator cannot easily correct bit drift by hand pressure the way a handheld drill allows. Cobalt bits resist the heat buildup that anneals a standard HSS bit’s cutting edge within a few holes in stainless. Cobalt is a through-hardened alloy, not a coating — it does not wear off, unlike titanium nitride on standard HSS.
M42 cobalt bit set: for hardened steel and sustained production drilling
An M42 set (8% cobalt) is the appropriate upgrade when the workpiece is hardened steel, high-nickel stainless, or when the shop runs sustained production drilling rather than occasional holes. Per manufacturer specifications, the higher cobalt content increases red hardness — the bit retains cutting-edge hardness at higher temperatures — at the cost of increased brittleness compared to M35. M42 bits chip more readily under lateral flex or a wobbling mag drill mount, so they are not automatically the better choice for a hand-held or unstable setup. Buy M42 only when M35 bits are visibly failing early on the current material, not as a default upgrade for shops that mostly drill mild steel.
Black-oxide HSS bit set: the mild-steel and aluminum budget option
Black-oxide-coated HSS bits are a reasonable choice for mild steel, aluminum, and light occasional-use fabrication where drilling volume is low and stainless or hardened material rarely appears. The black-oxide coating reduces friction and offers modest corrosion resistance during storage; it is not a substitute for cobalt’s heat tolerance, and per manufacturer data these bits dull faster than cobalt on stainless. This is the correct default for a farm shop or hobbyist bench drilling mostly mild steel and aluminum brackets — buying a cobalt set for that work is unnecessary spend.
Titanium-coated HSS bit set: sheet metal and mixed-material use
Titanium nitride (TiN) coated HSS bits suit sheet metal, mild steel, and wood in one set, which is useful for a shop that moves between materials without swapping bit sets. The coating reduces friction and extends life over uncoated HSS, but per manufacturer data it is a thin surface treatment that wears through with repeated resharpening, after which the bit performs as plain HSS. Titanium coating is not a substitute for cobalt on stainless or hardened steel.
Step drill bit: sheet metal and thin-wall tube, one bit per hole range
A step (unibit) drill bit cuts a progressively larger hole in a single tool, which is the practical choice for sheet metal, electrical boxes, and thin-wall tube where a twist bit tends to grab and deform the material at breakthrough. Per manufacturer specifications, step bits are rated for sheet and thin-wall stock only — pushing one through solid bar stock or thick plate wears the steps unevenly and does not produce a clean hole. Common ranges run 1/8-1/2 inch or 3/16-7/8 inch in a single bit, eliminating the need for a full twist-bit set on sheet work.
Matching bit material to the job
Per Machinery’s Handbook drilling guidance, speed and feed matter as much as bit material. Running a cobalt bit too fast on stainless generates the same work-hardening and heat failure as running a cheap HSS bit — material alone does not compensate for wrong speed, insufficient coolant, or excessive feed pressure. Lower RPM and steady feed pressure, with cutting fluid on stainless and harder alloys, extends bit life more than any single material upgrade.
For fixed-column drilling with the speed control and table rigidity to dial in correct RPM for the material, see the drill presses for metal guide. For portable structural steel work where a twist bit is impractical past 1/2 inch, annular cutters on a magnetic drill press — covered in the magnetic drill press guide — remove a plug rather than chips and cut faster in thick material. Shops stocking metal-drilling consumables typically also carry bandsaw blades for stock cutting and angle grinder discs for deburring the holes a drill bit leaves behind.
What fails first?
The cutting edge dulls first, almost always from heat rather than mechanical wear — a bit run too fast without coolant on stainless or hardened steel loses its temper at the tip within a few holes, visible as a bluish discoloration. Split points reduce walking but do not prevent this; only correct speed, feed, and coolant do. Titanium coating fails next, wearing through at the cutting edge after repeated use or resharpening, after which the bit behaves as uncoated HSS. Step bits fail differently — the steps wear unevenly when pushed into material thicker than rated, producing an out-of-round hole rather than a dulled edge. If a bit is walking, smoking, or discoloring on the first hole, the problem is usually speed or missing coolant, not the bit itself.
Who this is NOT for
This guide is not for masonry, concrete, or tile drilling — those require carbide-tipped or SDS bits, covered separately from twist and step bits for metal. It is not for production shops running thousands of holes per shift in hardened tool steel; that volume justifies solid-carbide or specialty coated bits beyond this consumer and small-shop range. Buyers drilling primarily wood or plastic do not need cobalt or M42 bits — standard HSS or brad-point bits are the appropriate and cheaper choice. And a dull or walking bit on a wobbling handheld drill is often a setup problem, not a bit problem; a drill press or mag drill fixes the geometry that a bit alone cannot.
Frequently asked questions
What drill bit is best for stainless steel?
An M35 or M42 cobalt bit with a 135-degree split point, run at low RPM with cutting fluid. Standard HSS bits work-harden and dull quickly on stainless because they lose cutting-edge hardness at the heat stainless generates.
Is cobalt or titanium-coated better for metal?
Cobalt is a through-hardened alloy that resists heat at the cutting edge and does not wear off; titanium nitride is a surface coating on HSS that wears through with use. Cobalt suits stainless or hardened steel; titanium-coated HSS is a reasonable lower-cost option for mild steel and mixed-material shop use.
Can a step bit replace a twist bit set?
Only for sheet metal and thin-wall tube within its rated range. Step bits are not rated for solid bar stock or thick plate — manufacturer data specifies sheet and thin-wall use, and pushing one into thicker material wears the steps unevenly.
Why does my drill bit turn blue and stop cutting?
Blue discoloration indicates the cutting edge overheated and lost its temper, usually from excessive speed, insufficient cutting fluid, or feeding too fast for the material. This applies to both HSS and cobalt bits — cobalt tolerates more heat before failing but is not immune to incorrect speed and feed.
What size drill bit set covers most metal shop work?
A 1/16-1/2 inch cobalt set in 1/64-inch increments (typically 29 pieces) covers the range most fabrication and repair work requires. Smaller 13-piece sets in 1/16-inch increments are a lower-cost option for shops that mostly drill common fractional sizes.
Sources
- IRWIN Industrial Tools, cobalt and HSS drill bit product specifications.
- DEWALT, titanium and cobalt drill bit product data.
- Milwaukee Tool, Shockwave and step bit product documentation.
- Drill Hog, M42 cobalt bit specifications.
- Machinery’s Handbook, 30th Edition, drilling speed and feed guidance.
- ANSI/ASME B94.11M, Twist Drill Standards.