Guide to Tool Steel Machining

What is tool steel machining?

Tool steel machining is cutting, shaping, or manipulating tool steel using machine tools such as lathes, milling machines, and grinders. Tool steel is high-strength, high-hardness steel designed to produce tools and dies. It is commonly used where durability and wear resistance is critical, such as in manufacturing cutting tools and molds. There are many different types of tool steel, including stainless steel, high-speed steel, and alloy steel, each with unique characteristics and properties.

When machining tool steel, it is important to select the right tool and fine-tune the machining parameters to ensure good tool life and accuracy. Tool steel can be machined more efficiently at high speeds and with coolant and has excellent dimensional stability and corrosion resistance. Tool steel is also resistant to abrasion and can be heat-treated to achieve different hardness levels.

Advantages of machining tool steel parts

  • Wear resistance:
    Tool steel is known for its high level of wear resistance, making it ideal for use in high-stress, high-wear applications such as cutting tools and dies.
  • Heat resistance: 
    Tool steel’s ability to withstand high temperatures without deforming or losing strength makes it suitable for hot working applications.
  • Ductility:
    Despite its strength and hardness, tool steel is relatively ductile, making it easier to machine and work with than other types of steel.
  • Versatility: 
    Tool steel can be machined into a wide range of shapes and sizes, making it a very versatile material for many applications.
  • Good toughness:  
    Tool steel has good toughness, which means it is resistant to cracking and breaking under stress. This makes it a good choice for applications where the parts may be subjected to impact or other load types.
  • Good machinability:
    Tool steel is typically easy to machine and work with, making it an attractive choice for many applications. By fine-tuning the machining parameters and using the right tooling, it is possible to achieve good results with tool steel.
  • Abrasion resistance:
    Tool steel is resistant to abrasion, which makes it suitable for use in applications where the parts may be subjected to abrasive wear.
  • Heat treatability: 
    Tool steel can be heat-treated to achieve different hardness levels and desired properties, making it versatile and adaptable to different applications.

Applications for tool steel machining

Tool steel is used in many applications where durability and wear resistance are critical. Some common examples of applications for tool steel machining include:

Cutting tools:

Tool steel is often used to manufacture cutting tools such as lathe tools, milling cutters, and drill bits.


Tool steel is commonly used to manufacture dies for stamping, forging, and other metalworking processes.


Tool steel is often used in the production of molds for injection molding, blow molding, and other plastic molding processes.

Machine components:  

Tool steel is used to manufacture various machine components such as gears, bearings, and shafts.

Hand tools: 

Tool steel is also used to produce hand tools such as hammers, pliers, and screwdrivers.

Automotive parts: 

Tool steel is used to produce various automotive parts, such as engine blocks and transmission gears.

Common Tool steel alloys 

Tool steel D2

D2 tool steel has remarkable wear resistance because it is air-hardening, cold-work, high-carbon, and high-chromium.

D2 tool steel features include low heat-treatment distortion, good toughness, and wear resistance at the expense of grindability and machinability. It can withstand chipping and fracture because of its deep hardening capability.

D2 tool steel’s pricing and properties make it an excellent choice for long-term, high-production die applications. These include its dimensional stability during heat treatment, toughness, and wear resistance.

Tool steel A2

When improved dimensional stability, machinability, and hardening safety are required, A2 tool steel is the better option over O1 tool steel. This chromium alloy dies steel is an air hardening and cold worked.

A2 tool steel is an excellent all-purpose grade because it possesses moderate wear resistance at a cost that falls between O1 and D2 tool steel.

A2 tool steel is ideal for longer production runs on light or heavy gauge stock because of its higher wear resistance and lesser distortion.

Tool steel S7

In addition to its high toughness, machinability, and dimensional stability after heat treatment, S7 tool steel also has excellent impact qualities.

S7’s shock resistance, size stability, and machinability make it ideal for a wide variety of applications where the tool temperature won’t exceed 1000°F, and its air-hardening properties make it useful in cold and hot work tooling.

Tool steel O1

Because of its low hardening temperatures and simple machining characteristics, O1 tool steel is a popular general-purpose steel.

O1’s wear resistance and hardness are up to the task of standard tool and die applications, making it an excellent material for tooling that serves its purpose well and allows for efficient and cost-effective manufacturing. As a result of its increased hardening size stability, A2 is a good option in certain circumstances.

Tool steel H13

Known for its air-hardening properties and its suitability for hot work, H13 tool steel contains 5% chromium. Because of its high red hardness and resilience to shock and abrasion, it is often used in die casting. Its versatility and resistance to rapid cooling from high working temperatures make it an ideal material for extrusion dies, plastic molds, and die casting.

Although H13 tool steel was created to be used in various hot work applications, it has also proven beneficial in cold work settings, especially when greater toughness is prioritized above greater wear resistance.

Tool steel A3

A3 is a high-chromium, medium-carbon tool steel with exceptional durability and wear resistance. It finds widespread application in the fabrication of blades and mold-forming dies, and the material’s durability and resistance to deformation make it perfect for stamping and shaping dies.

Tool steel machining considerations

The several considerations to keep in mind when machining tool steel are:

  • Hardness: Tool steel is known for its high hardness, which makes it difficult to machine. It is important to use sharp cutting tools and take light cuts to prevent tool breakage or damage to the workpiece.
  • Chip control: Tool steel tends to produce long, stringy chips, which can lead to chip packing and heat buildup. Using chip breakers and proper chip control techniques can help to prevent these issues.
  • Heat treatment: Many tool steel grades are heat treated to enhance their performance. It is important to consider the heat treatment of the material when machining, as some heat-treated grades may be more difficult to machine than others.
  • Cutting fluids: A cutting fluid can help improve tool life and surface finish when machining tool steel. Choosing a cutting fluid suitable for the specific tool steel grade being machined is important.
  • Surface finish: A good surface finish when machining tool steel can be challenging due to its high hardness. Using sharp cutting tools and taking light cuts can help to improve the surface finish.


Tool steel machining involves the use of specialized tools and techniques to shape and finish various alloys of steel, including stainless steels and oil hardening steels, as well as other metals such as aluminum and molybdenum.

The tool path and work material are important considerations in the machining process, as are the properties of the materials being worked on, such as their toughness, edge retention, and abrasion resistance. Tungsten carbide, nickel, and iron are common materials used in tool steel machining.

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