T4 vs M35
These two grades are listed as equivalents of each other: their chemistry windows overlap and they serve the same applications. They are not always identical — check the differences below before substituting, especially in certified designs.
T4
Tool Steel
T4 adds about 5% cobalt to the T1 base for extra red hardness in heavy cuts and roughing work. It is a legacy grade, largely replaced by M35/M42 in new tooling but still specified on older drawings.
Standards: DIN — (HS18-0-1-5 family) · AISI T4 · JIS SKH3 (near) · GB W18Cr4VCo5 (near)
M35
Tool Steel
M35 is M2 with about 5% cobalt added, the most popular cobalt high-speed steel worldwide. The cobalt raises red hardness so tools keep cutting at the higher speeds and feeds used on stainless and alloy steels.
Standards: DIN 1.3243 · AISI M35 · JIS SKH55 · GB W6Mo5Cr4V2Co5
Chemical composition compared (%)
| Element | T4 | M35 |
|---|---|---|
| C | 0.70–0.80 | 0.87–0.95 |
| Si | ≤0.40 | ≤0.45 |
| Mn | ≤0.40 | ≤0.40 |
| Cr | 3.75–4.50 | 3.75–4.50 |
| W | 17.25–18.75 | 5.90–6.70 |
| V | 0.80–1.20 | 1.70–2.10 |
| Co | 4.25–5.75 | 4.50–5.00 |
| Mo | — | 4.70–5.20 |
Properties compared
| Property | T4 | M35 |
|---|---|---|
| Delivery condition | Annealed | Annealed |
| Hardness (hardened) | 63–66 HRC | 63–66 HRC |
| Density | 8.60 g/cm³ | 8.10 g/cm³ |
| Red hardness | Higher than T1 (cobalt) | Higher than M2 (5% cobalt) |
Sourcing either grade?
Nasteel stocks both families from Shenzhen with EN 10204 3.1 mill certificates by heat number.
Ask for a quotationSee full data sheets: T4 · M35. Substitution decisions for certified parts stay with the design authority.