# O1 tool steel equivalents

O1 tool steel is nearest to EN 1.2510 (100MnCrW4), JIS SKS3 and China GB 9CrWMn. These are nearest equivalents, not identical grades: the governing standard or mill certificate decides.

| System | Designation |
|---|---|
| AISI / ASTM / SAE | O1 |
| EN steel name | 100MnCrW4 |
| EN steel number | 1.2510 |
| JIS | SKS3 |
| China GB | 9CrWMn |

Family: Cold-work tool steel, oil-hardening

## What it is

An oil-hardening cold-work tool steel. It hardens at a relatively low temperature, which makes it a favourite for small shops and toolrooms.

## Typical uses

Gauges, punches, short-run dies, knives, bushings and general toolroom parts.

## Machining notes

Machines well in the annealed condition. Ground flat stock is widely available.

## Related grades

- A2 tool steel (1.2363): Air-hardening, less distortion
- D2 tool steel (1.2379): Higher wear resistance

Equivalents are nearest matches, not identical grades. The governing standard or mill certificate decides.

## FAQ

**What is the European equivalent of O1 tool steel?**
The nearest EN grade is 1.2510, steel name 100MnCrW4.

**What is the JIS equivalent of O1 tool steel?**
The nearest Japanese grade is SKS3.

**What is the Chinese GB equivalent of O1 tool steel?**
The nearest Chinese GB grade is 9CrWMn.

**Is 1.2510 the same as O1?**
1.2510 (100MnCrW4) is the nearest European equivalent of O1, not an identical grade. Composition limits and required properties differ in detail, so check the governing standard or the mill certificate when it matters.

**What is O1 used for?**
Gauges, punches, short-run dies, knives, bushings and general toolroom parts.

Source page: https://machinistcharts.com/material/o1-tool-steel/
Updated: 2026-10-06
Publisher: MachinistCharts (https://machinistcharts.com)