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A solid carbide drill bit set is worth buying if you drill hardened steel, stainless, cast iron, abrasive composites or circuit boards on a drill press, mill or CNC machine, because carbide stays sharp at temperatures and speeds that would ruin high-speed steel (HSS) or cobalt. It is a poor choice for a handheld cordless drill: carbide is very hard but brittle, and the wobble and side load of freehand drilling snap small carbide bits easily. For most handheld metal drilling, a cobalt (M35 or M42) set is the better tool.
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What we cover
Solid carbide vs cobalt vs HSS
| Property | HSS (M2) | Cobalt (M35/M42) | Solid carbide |
|---|---|---|---|
| Typical hardness | ~62-65 HRC | ~65-68 HRC | ~90+ HRA (far harder than tool steel) |
| Heat resistance | Softens around 600 C | Somewhat better than HSS | Keeps hardness well above 800 C |
| Toughness (shock resistance) | High | Medium-high | Low (brittle) |
| Cutting speed in mild steel | ~80-100 SFM | ~90-120 SFM | ~250-400 SFM |
| Typical point angle | 118 degrees | 135 degrees split | 135-140 degrees |
| Handheld drill use | Yes | Yes | Not recommended |
| Typical price, 1/4 in jobber-length bit | $2-$6 | $5-$12 | $15-$60 |
Types of solid carbide sets you will see
| Set type | Typical sizes | Typical price | Use |
|---|---|---|---|
| PCB / micro drill set | 0.3-1.2 mm, often 10-50 bits, 1/8 in (3.175 mm) shank | $15-$50 | Circuit boards, model making, jewelry, desktop CNC |
| Small metric or fractional set | 1-6 mm or 1/16-1/4 in, 5-13 bits | $60-$250 | Drill press and mill work in steel and stainless |
| Hardened-steel set (coated) | 3-10 mm, 5-10 bits, TiAlN/AlTiN coated | $150-$500 | Hardened tool steel, broken-tap removal setups |
| Machinist sets from industrial brands | Jobber or stub length, coolant-through options on larger sizes | Sold mostly as individual bits | Production CNC |
Industrial carbide drills from brands such as OSG, Guhring, YG-1 and Kennametal are usually sold as individual sizes rather than boxed sets, because production shops buy only the diameters they need. Boxed carbide sets are more common at the PCB and small-hobby end of the market.
Worked example: running speed for carbide
The biggest mistake new carbide users make is running it at HSS speeds, which rubs instead of cutting and dulls the edge. Use the standard formula:
RPM = (SFM x 3.82) / drill diameter in inches (or, in metric, RPM = cutting speed in m/min x 1000 / (3.14 x diameter in mm)).
| Drill | Material | Surface speed | Calculated RPM |
|---|---|---|---|
| 1/4 in HSS | Mild steel | 90 SFM | ~1,375 |
| 1/4 in carbide | Mild steel | 300 SFM | ~4,580 |
| 1/4 in carbide | 304 stainless | 150-200 SFM | ~2,300-3,050 |
| 6 mm carbide | Cast iron | ~90 m/min | ~4,770 |
| 1 mm carbide | FR4 circuit board | High | Typically 10,000-30,000+ on a spindle |
Many benchtop drill presses top out around 3,000 RPM, so you may not reach ideal carbide speeds on small diameters. That is acceptable: run as fast as the machine allows, and use a steady, firm feed so the edge cuts rather than rubs.
What setup carbide needs
- Rigidity. A drill press, mill or CNC with low spindle runout. Freehand drilling with a cordless drill side-loads the bit and is the leading cause of breakage.
- Good workholding. Clamp the work in a vise; any movement at breakthrough can snap the drill.
- A precision chuck or collet. Collets give less runout than a typical three-jaw keyed chuck, which extends tool life.
- Coolant or lubricant. Flood coolant on machines; cutting fluid or mist on a drill press. Do not let carbide heat up dry and then dunk it in cold fluid, which can cause thermal cracking.
- Peck drilling for deep holes. Retract every one to three diameters to clear chips, unless the drill has internal coolant.
Length matters more with carbide
Carbide drills come in stub, jobber and longer series lengths, and with brittle material the shortest length that reaches your hole depth is always the safest choice. A stub-length drill flexes far less, so it starts on center and resists snapping when it hits a hard spot. Jobber-length carbide is fine for through holes in plate up to a few diameters deep on a rigid machine. Long-series carbide is a specialist tool; for deep holes on a manual machine, start with a short carbide drill, then follow with a longer drill once the hole is established. When you compare sets, check the flute length against the thickness of the material you usually drill rather than buying the longest bits on offer.
Is a carbide set right for you?
| Your situation | Recommendation |
|---|---|
| Hobbyist with a cordless drill drilling steel brackets | Cobalt M35 set instead |
| Drill press owner drilling stainless or hardened parts | Small carbide set in 3-6 mm or 1/8-1/4 in |
| Desktop CNC or PCB work | PCB micro carbide set with 1/8 in shanks |
| Machine shop, repeat jobs | Individual industrial carbide drills in needed sizes |
| Removing a broken tap or hardened bolt | Carbide bit or carbide burr with a rigid setup; otherwise consider EDM services |
Durability and what goes wrong
- Chipped corners. The outer corners of the cutting edge chip first from vibration or interrupted cuts. A chipped drill makes oversized, rough holes and should be reground or replaced.
- Breakage at breakthrough. As the point exits, the drill can grab. Reduce feed for the last part of the hole.
- Coating wear. TiAlN or AlTiN coatings help in steel and stainless; on aluminum, uncoated or specially coated carbide avoids built-up edge.
- Regrinding. Carbide needs a diamond wheel. Many tool-sharpening services regrind larger carbide drills at a fraction of replacement cost; micro drills are usually treated as consumables.
- Storage. Keep bits in individual slots or tubes; carbide edges chip if bits rattle against each other.
Safety
Carbide fails suddenly and sends fragments flying, so always wear safety glasses or a face shield. Never hold small parts by hand on a drill press, and keep hands clear of rotating chucks. Carbide grinding dust contains cobalt binder and should not be inhaled; use wet grinding and a respirator if you sharpen bits yourself.