SKS3 vs O1
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.
SKS3
Tool Steel
SKS3 is the JIS oil-hardening alloy tool steel — the Japanese counterpart of AISI O1 / DIN 1.2510, a Mn-Cr-W grade that hardens in oil with low distortion for gauges and short-run cold work tooling.
Standards: DIN 1.2510 (105WCr6, near) · AISI O1 · JIS SKS3 (JIS G4404) · GB 9CrWMn
O1
Tool Steel
O1 is a general-purpose oil-hardening tool steel — cheap, easy to heat treat with basic equipment, and dimensionally stable enough for short-run tooling.
Standards: DIN 1.2510 · AISI O1 · JIS SKS3 · GB 9CrWMn
Chemical composition compared (%)
| Element | SKS3 | O1 |
|---|---|---|
| C | 0.90–1.00 | 0.85–0.95 |
| Si | ≤0.35 | 0.10–0.40 |
| Mn | 0.90–1.20 | 1.00–1.20 |
| P | ≤0.030 | — |
| S | ≤0.030 | — |
| Cr | 0.50–1.00 | 0.50–0.70 |
| W | 0.50–1.00 | 0.50–0.70 |
| V | — | 0.05–0.15 |
Properties compared
| Property | SKS3 | O1 |
|---|---|---|
| Delivery condition | Annealed | Annealed |
| Hardness (hardened) | 58–62 HRC | 57–62 HRC |
| Density | 7.85 g/cm³ | 7.85 g/cm³ |
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: SKS3 · O1. Substitution decisions for certified parts stay with the design authority.