HSS, cobalt and carbide drill bits are often sold side by side, but they are not interchangeable. The best choice depends on workpiece material, machine rigidity, hole tolerance, drilling depth and budget.
Quick comparison table
| Drill material | Strength | Best use |
|---|---|---|
| HSS | Economical and flexible | Mild steel, aluminum, plastics and general workshop drilling |
| Cobalt HSS | Better heat resistance | Stainless steel and harder metal drilling |
| Carbide | High hardness and wear resistance | Rigid CNC, abrasive materials and high-volume precision holes |
HSS drill bits
HSS is the practical starting point for general metal drilling. It is cost-effective, less brittle than carbide and suitable for hand drills, bench drills and maintenance use.
Cobalt drill bits
Cobalt grades such as M35 and M42 improve hot hardness. They are useful for stainless steel and tougher alloys where normal HSS loses edge quickly. However, cobalt still needs correct speed, feed and lubrication.
Carbide drill bits
Carbide is hard and wear-resistant, but it is less forgiving. It performs best on rigid machines with accurate tool holding. In unstable handheld work, carbide can chip before its wear resistance becomes useful.
Material selection by workpiece
| Workpiece | Suggested starting point | Note |
|---|---|---|
| Mild steel | HSS or cobalt | Cobalt if heat or volume is high |
| Stainless steel | Cobalt or carbide | Control heat and work hardening |
| Aluminum | Sharp polished HSS/cobalt/carbide | Prevent chip welding |
| Hardened or abrasive materials | Carbide | Needs rigid setup |
Do not choose by material grade alone
A premium drill can fail if the shank slips, the spindle runs out, chips pack in the flute or the feed is too low. Tool material is only one part of the drilling system.
Related guide: Drill Bit Coating Color Guide: Black Oxide, TiN, TiAlN and Bright Finish adds a practical buyer checklist for drill bit coating color guide.
Related Wryno guides
Continue with M35 vs M42 cobalt drill bits, best drill bits for stainless steel, best drill bits for aluminum, and drill bit materials explained.