O1 Tool Steel Properties, Chemical Composition, Uses and Specifications


O1 Tool Steel is a type of oil-hardening, general-purpose tool steel that is characterized by its good toughness and excellent dimensional stability. It is commonly used for making tools for woodworking, metalworking, and leatherworking.

Here are the specifications that O1 Tool Steel typically meets:


  • Carbon: 0.9% - 1.1%
  • Manganese: 0.3% - 0.5%
  • Chromium: 0.3% - 0.5%
  • Tungsten: 0.8% - 1.2%
  • Silicon: 0.15% - 0.35%


  • Rockwell hardness (C scale): 60 - 62
  • Vickers hardness: 240 - 260


  • Good toughness at low to moderate hardness levels

Wear resistance:

  • Good wear resistance, particularly in applications where the tool is subjected to repeated impact loads or abrasive wear


  • Good machinability, especially when compared to other tool steels.

Heat treatment:

  • Typically, oil-hardened and tempered to obtain the desired hardness and toughness.


  • Woodworking tools (e.g., chisels, plane blades, carving tools)
  • Metalworking tools (e.g., punches, dies, reamers)
  • Leatherworking tools (e.g., knives, punches, stitching chisels)
  • Knives
  • Gauges and measuring tools

Note that these specifications may vary slightly depending on the manufacturer and the specific product. It is always a good idea to consult the manufacturer's specifications to ensure that the product meets your specific requirements.

O1 Tool Steel Heat treatment

O1 Tool Steel is typically heat-treated to improve its hardness, toughness, and wear resistance. The standard heat treatment process for O1 Tool Steel is as follows:

  1. Oil hardening: The steel is heated to a temperature between 830°C to 860°C (1526°F to 1580°F), and then slowly cooled in oil. This process increases the steel's hardness, but also makes it more brittle.

  2. Tempering: The oil-hardened steel is then tempered by heating it to a lower temperature, typically between 150°C to 200°C (302°F to 392°F), and then slowly cooling it. This process reduces the steel's brittleness and increases its toughness.

It's important to note that the precise heat treatment procedure can vary depending on the desired end-use properties of the tool, and the specific requirements of the application. The heat treatment process should always be carried out by a qualified professional, who is familiar with the material, the equipment, and the desired end-use properties.

In general, O1 Tool Steel is a versatile material that is well-suited to a wide range of applications, and the heat treatment process can be customized to meet specific requirements. To obtain optimal results, it is recommended to consult a metallurgical specialist or the steel manufacturer for guidance on the most appropriate heat treatment procedure for your specific application.

Standards and Designations:


  • ASTM A681 - Specification for Steel, Tool, Carbon, and Alloy


  • SAE/AISI O1 - AISI designation for a type of oil-hardening tool steel


  • MIL T-44076 - Military specification for oil-hardening tool steel


  • UNS T31501 - UNS designation for O1 Tool Steel