SteelWhat is O1 steel and what is it used for? Cold work tool steel
O1 steel is a cold work tool steel. In this guide we explain what O1 steel is, its chemical composition, hardness, how it is heat treated, what it is used for and the sizes we stock.
What is O1 steel?
The classic oil-hardening tool steel, alloyed with manganese-chrome-tungsten. Very good machinability, high as-quenched hardness and low cost. For small tools and short-run dies.
Chemical composition of O1 steel
This is the typical composition of O1 steel (AISI O1 / EN-DIN 1.2510 / JIS SKS3 standard):
| Element | Contents | What for? |
|---|---|---|
| Carbon (C) | 0.85 – 1.00 % | Hardness and wear resistance |
| Silicon (Si) | 0.10 – 0.50 % | Deoxidizer |
| Manganese (Mn) | 1.00 – 1.40 % | Hardenability |
| Chromium (Cr) | 0.40 – 0.70 % | Hardenability and wear resistance |
| Tungsten (W) | 0.40 – 0.60 % | Forms very hard carbides (cutting and wear) |
| Vanadium (V) | 0.30 % max. | Refines the grain and forms hard carbides |
| Phosphorus (P) | 0.030 % max. | Impurity, kept low |
| Sulfur (S) | 0.030 % max. | Impurity, kept low |
Hardness and heat treatment of O1 steel
The typical working hardness of O1 is 57 – 62 HRC. It is oil-quenched and tempered. It is easy to machine and reaches good hardness at low cost, ideal for small tools and short runs. You can see the full overview in our article on heat treatments for steel, and hardness scales in steel hardness.
What is it for? Applications of O1
O1 steel is mainly used in:
- Cutting dies
- Precision punches
- Forming dies
- Industrial knives
- Precision gages
- Master gages
- Threading taps
- Reamers
- Cutting broaches
Forms and sizes we carry
At NAT MAC we stock O1 steel in these forms and sizes:
| Package size | Sizes |
|---|---|
| Round bars | Ø 1/8" – 2" (Ø 3 – 51 mm) |
| Plates | 1/8" – 12" (3 – 305 mm) |
If you need a particular size, tell us which one and we will gladly source it for you.
O1 equivalents and standards
O1 steel is also identified by these standards: AISI O1 / EN-DIN 1.2510 / JIS SKS3. You can see how to read them in our article on steel standards.
In summary
- O1 is a cold work tool steel
- Typical composition: C 0.85 – 1.00 and Cr 0.40 – 0.70, plus alloying elements
- Typical working hardness: 57 – 62 HRC
- Ideal for economical, easy-to-machine cold work
- We carry it in round bar (1/8" – 2") and plates (1/8" – 12"), cut to size
Why buy your O1 steel at NAT MAC?
We have more than 54 years of experience as an industrial supplier and ISO 9001 certified quality. We carry a wide range of tool grade steels and help you choose the right one for your tool or mold.
- Quality O1 Steel, backed and traceable
- Material cut to the size you need
- Technical advice on choosing the right grade
- Wide range of tool-grade steels in stock
- On-time deliveries and competitive prices
Tell us what tool or mold you are going to make and in what dimensions, and we will recommend the right grade and form. Request your free quote.
Sources: data sheet from our NAT MAC catalog (composition, sizes and applications) and public industry references for working hardness. Values are for reference and may vary by standard, heat and treatment.
