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How To Machining or Milling Tool Steel?
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Machining and milling tool steel present significant challenges due to its inherent hardness and exceptional wear resistance. As a professional manufacturer, we recommend machining tool steel in its annealed state, as this softens the material, making it easier to cut and shape.
If you require tool steel products with turning, grinding, or milling, please contact SteelPro Group for tailored solutions.
Factors Affecting Machinability of Tool Steel
Hardness
Tool steels are recognized for their elevated hardness, which makes them challenging to machine and shape. Hardness is commonly measured on the Rockwell C scale, ranging from 40 to 70 HRC. As hardness increases, the material becomes more resistant to wear but harder to machine.
Alloy Composition
Tool steels often contain a mix of elements such as chromium, vanadium, molybdenum, and tungsten. These elements enhance properties like abrasion resistance, durability, and heat resistance. However, they can also make machining more difficult.
Heat Treatment
Tool steels undergo heat treatment processes like quenching and tempering to achieve their desired hardness and toughness. The heat treatment process affects the steel’s microstructure and its machinability. An annealed state is recommended for machining.
Preparing for Machining or Milling Tool Steel
Tool Selection
When machining tool steel, it is critical to select cutting tools that can withstand the material’s hardness and toughness. Recommended tool materials include:
Carbide Tools: Carbide is the most common choice due to its high hardness and wear resistance. It remains sharp at high temperatures, which is crucial when cutting tool steel.
High-Speed Steel (HSS): Although not as long-lasting as carbide, high-speed steel tools are still efficient for machining tool steel, particularly for more moderate cuts.
Cobalt Alloys: Cobalt-based tools are harder than standard HSS, offering better heat resistance and longer tool life when machining high-hardness materials.
For coatings, consider tools with TiN (Titanium Nitride) or TiAlN (Titanium Aluminum Nitride) coatings. These coatings lower friction, assist in heat dissipation, and enhance tool durability
Workpiece Preparation
Before machining tool steel, ensure that the workpiece is properly prepared:
- Workholding: Secure the workpiece tightly using clamps, vises, or fixtures. A loose workpiece can shift during machining, resulting in inaccuracies and damage to both the workpiece and the cutting tool.
- Workpiece Orientation: Ensure the workpiece is aligned properly to minimize deflection and vibration during cutting. This is particularly important for tool steels that are tougher to machine.
How To Machining Tool Steel?
Turning
Use slow cutting speeds (between 50 and 150 SFM) with a moderate feed rate. Choose a tool with a strong cutting edge, such as a carbide insert, and ensure proper cooling to avoid tool wear.
Milling
When milling tool steel, a cutter with multiple teeth is ideal for distributing the cutting forces. To prevent overheating, use a low cutting speed but a higher feed rate compared to turning. For slot milling or face milling, carbide end mills with coatings like TiAlN are effective at high temperatures.
Drilling
When drilling, use drills with coatings that offer high heat resistance, such as TiN or TiAlN. Apply steady coolant to prevent accumulation of chips and decrease heat at the cutting edge. Speeds should be lower than typical drilling speeds for softer materials.
Grinding
Tool steels are often ground to achieve high precision. Use a fine-grit grinding wheel to avoid excessive heat generation, which can affect the material properties. Proper coolant is essential during grinding operations.
Types of Tool Steel and Machining Considerations
Cold Work Tool Steel
Cold-work tool steels (e.g., A2, D2, O1) are prone to work hardening, which increases tool wear.
- Use carbide tools with coatings like TiN or TiAlN for better wear resistance. Maintain slower cutting speeds (100–150 SFM) and controlled cooling to prevent overheating and premature tool wear.
Hot-Work Tool Steel
Hot-work steels are designed to endure high temperatures during processing, commonly used for molds and forging dies.
- Use HSS or carbide tools with proper lubrication to minimize heat and prevent tool wear. Opt for slower feed rates and lower cutting speeds.
High-Speed Steel (HSS)
HSS can be machined at higher speeds compared to other tool steels.
- Use carbide inserts for best results. Higher cutting speeds (up to 300 SFM) can be used, but feed rates are based on the hardness of the specific steel.
Shock-Resistant Tool Steel
Shock-resistant tool steels like S7 are easier to machine but require care to avoid work hardening.
- Use lower cutting speeds and higher feed rates to prevent excessive heat buildup and work hardening.
Plastic Mold Steel
While they are relatively easier to machine compared to other tool steels, ensuring proper surface finish is crucial for molding precision.
- Use high-speed steel (HSS) or carbide tools for efficient cutting. Medium cutting speeds (150–200 SFM) and moderate feed rates are recommended. Flood coolant or air blast helps control temperature.
Stainless Tool Steel
Stainless steels, such as 440C, can be tough to machine because of their high strength and hardness.
- Use carbide tools with TiN or TiAlN coatings. Cutting speeds should range from 80 to 150 SFM, depending on the steel grade. Low feed rates and adequate cooling are essential to avoid tool wear and heat buildup.
Get Expert Machining Solutions for Tool Steel
If you’re facing challenges machining or milling tool steel, SteelPro Group is here to help. We offer customized solutions and high-quality tool steel products. Our team is here to support you with expert advice and precise machining services tailored to your needs.