Cutting tool materials trade toughness for hardness and heat resistance. Tougher materials survive interrupted cuts; harder ones run faster and last longer in clean cuts. The speeds below are rough multiples relative to plain HSS.
| Tool material | Relative speed | Best for |
|---|---|---|
| HSS | 1× (baseline) | General work, taps and drills, interrupted cuts |
| Cobalt HSS (M42) | ~1.5× | Tougher materials; better heat resistance than HSS |
| Uncoated carbide | 3–4× | Most milling and turning |
| Coated carbide | 4–6× | Production work in steel and stainless |
| Ceramic | 8–10× | Hard turning and cast iron at high speed |
| CBN | 10×+ | Hardened steel above ~45 HRC |
| Diamond (PCD) | 10×+ | Abrasive non-ferrous and composites — never steel |
Relative figures — real tool life depends on material, coating, coolant, and rigidity. As a rule, the harder the tool, the faster it runs but the more it dislikes shock and interruption.
Pair this with the Tool Coating Comparison and Feeds and Speeds Chart.