W1 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.
W1
Tool Steel
W1 is the classic water-hardening carbon tool steel, ordered by carbon class from about 0.70% to 1.30% C. It forms a very hard thin case over a tough soft core — the oldest tool steel still in daily use.
Standards: DIN 1.1545 (C105W1, by carbon class) · AISI W1 · JIS SK3 family (by carbon class) · GB T10 (near, by carbon class)
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 | W1 | O1 |
|---|---|---|
| C | 0.70–1.30 (by carbon class) | 0.85–0.95 |
| Si | 0.10–0.40 | 0.10–0.40 |
| Mn | 0.10–0.40 | 1.00–1.20 |
| Cr | — | 0.50–0.70 |
| W | — | 0.50–0.70 |
| V | — | 0.05–0.15 |
Properties compared
| Property | W1 | O1 |
|---|---|---|
| Delivery condition | Annealed | Annealed |
| Hardness (hardened) | 58–65 HRC (surface, shallow case) | 57–62 HRC |
| Density | 7.85 g/cm³ | 7.85 g/cm³ |
| Hardenability | Shallow (water quench) | — |
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: W1 · O1. Substitution decisions for certified parts stay with the design authority.