M42
Data verifiedM42 is a molybdenum-cobalt high-speed steel reaching 67–70 HRC, the hardest of the widely stocked conventional HSS grades. It cuts hardened steels, superalloys and other materials that destroy M2 tooling.
Chemical composition
| Element | Content (%) |
|---|---|
| C | 1.05–1.15 |
| Si | ≤0.45 |
| Mn | ≤0.40 |
| Cr | 3.50–4.25 |
| Mo | 9.00–10.00 |
| W | 1.15–1.85 |
| V | 0.85–1.25 |
| Co | 7.75–8.75 |
Weight percent, per the governing standard ranges. Actual values per heat are on the mill certificate.
Properties
| Delivery condition | Annealed |
| Hardness (hardened) | 67–70 HRC |
| Density | 7.90 g/cm³ |
| Red hardness | Excellent — top of the conventional HSS range |
Heat treatment
Preheat 850 °C; harden 1175–1205 °C; triple temper 540–560 °C.
Equivalent grades
| Standard | Designation |
|---|---|
| din | 1.3247 |
| aisi | M42 |
| jis | SKH59 |
| gb | W2Mo10Cr4VCo8 |
Compare side by side: M42 vs M35 · M42 vs M2
Equivalents overlap in chemistry and use but are not always identical — see our equivalents guide before substituting in certified designs.
Applications & Processing
Applications: Broaches, gear hobs, end mills, drills for aerospace alloys, saws, taps for hardened steels.
Processing: Brittle at full hardness — rigid setups and conservative feeds. Grind with CBN; avoid overheating the edge.
FAQ
- Why is M42 ground with CBN?
- At 68+ HRC with hard carbides, aluminum-oxide wheels dull and burn the edge; CBN keeps the edge geometry and finish.
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Ask for a quotationVisit NasteelSource: ASTM A600 / EN ISO 4957 published ranges · Last updated 2026-11-03. Data is indicative — verify critical values against the governing standard and mill certificate before use.