Cutting through iron like it’s mud? Sounds too good to be true, right?
Well, not if you’re equipped with the right cutting tool materials.
In this comprehensive guide, we delve into the five main materials used for cutting tools on machine tools. From high-speed steel to ceramics, we analyze each material’s unique properties and why they enable tools to slice through even the toughest metals like butter.
Whether you’re a machinist or simply curious about the science behind metal cutting, this guide is a must-read.
So, join us on this journey of discovery as we explore the world of cutting tool materials and uncover the secrets to achieving a clean, precise cut every time.
Types of Cutting Tool Materials
High-speed steel is a type of tool steel that is known for its high hardness, high wear resistance, and high heat resistance, achieved through the addition of elements such as tungsten, molybdenum, chromium, and vanadium. Also known as high-speed tool steel or hot-work steel, it is commonly referred to as “white steel.”
High-speed steel is primarily used to create complex, lightweight, and impact-resistant metal cutting tools. The manufacturing process of high-speed steel tools is straightforward and allows for easy sharpening, which is why they still make up a significant proportion of metal cutting tools despite the emergence of newer materials.
2. Cemented carbide
Cemented Carbide is an alloy made of refractory metals and binder metals, produced through P/M metallurgical techniques. This material has excellent properties such as high hardness, wear resistance, good strength and toughness, heat resistance, and corrosion resistance.
In particular, its high hardness and wear resistance remain constant even at temperatures up to 500°C, and it still has a high hardness at 1000°C. Thus, cemented carbide has a higher cutting performance compared to high-speed steel and can improve the durability of the tool several to dozens of times.
With the same durability, cemented carbide allows for cutting speeds to increase by 4-10 times. As a result, it is widely used as a tool material, capable of cutting difficult-to-machine materials such as heat-resistant steel, stainless steel, high manganese steel, and tool steel.
Diamond is considered to be the hardest substance with exceptional thermal conductivity among known mineral materials. Its friction wear with various metal and non-metal materials is only 1/50-1/800 of cemented carbide, making it the ideal material for cutting tools.
Mostly, the cutting tools are made of artificial single crystal diamonds. The cutting edge of diamond tools is incredibly sharp, which is important for cutting chips with small sections. Its cutting edge has a low roughness and low friction coefficient, making it unlikely to produce chipping during cutting, thus resulting in high-quality machined surfaces.
There are three types of diamond cutting tools: natural single crystal diamond tools, solid synthetic single crystal diamond tools, and diamond compound tools. However, natural diamond tools are rarely used in actual production due to their high cost.
4. Cubic boron nitride
It is a newly developed artificially synthesized material, sintered from CBN (Cubic Boron Nitride) powder and a small amount of binder (such as Co-Ni, TiC, TiN, or Al2O3) under high temperature and pressure and with the help of a catalyst. It boasts high hardness, good abrasion resistance, exceptional chemical stability, and higher thermal stability compared to diamond tools.
It can maintain its properties even when used at temperatures between 1200-1300°C and does not react with metals in the iron group, making it ideal for processing steel. Hence, CBN cutting tools are primarily used for efficient machining of difficult-to-machine materials and have a broad range of applications in the machining industry.
The main advantages of ceramic tool materials are their high hardness and resistance to abrasion, as well as minimal reduction in bending strength and resistance to bending at high temperatures.
They have high chemical stability, low affinity with metals, and good resistance to oxidation at high temperatures. They do not react with steel even at melting temperatures, resulting in less adhesion, diffusion, and oxidative wear, and a lower coefficient of friction. Chips are also less likely to stick to the cutting tools and it is less likely to produce chipping.
However, the disadvantages of ceramic tools include high brittleness, low strength and toughness, and weaker bending strength compared to cemented carbide.
Selection Criteria for Cutting Tool Materials
When choosing cutting tool materials, it’s essential to consider various factors to ensure optimal performance and longevity. In this section, I’ll discuss my key considerations when selecting cutting tool materials: Strength and Hardness, Toughness, Wear Resistance, Thermal Stability, and Affordability.
Strength and Hardness
Strength and hardness determine a material’s ability to withstand the cutting forces and stresses experienced during machining operations. I typically consider the following when evaluating these properties:
- High tensile strength: This allows the cutting tool to resist deformation and fracture under cutting loads.
- High hardness: This ensures the material has excellent resistance to wear and cutting edge deformation.
Toughness is a crucial factor as it measures a material’s ability to absorb energy and resist fracture or chipping. When I evaluate the toughness of a cutting tool material, I consider:
- Resistance to chipping: The cutting tool should be able to maintain its cutting edge without any chipping, which can affect the quality of the machined part.
- Impact resistance: The material should withstand sudden loads and impacts encountered during intermittent cutting operations.
Since the cutting tool continually experiences friction during machining processes, wear resistance is a critical consideration. I focus on:
- Resistance to abrasive wear: Reducing the cutting edge’s wear rate ensures the cutting tool retains sharpness and accuracy.
- Resistance to adhesive wear: The material should prevent any bonds from forming between the tool’s surface and workpiece, leading to material transfer and, ultimately, wear.
As cutting tools generate high temperatures during machining, thermal stability is vital. I consider a material’s ability to:
- Withstand high temperatures: The cutting tool material should maintain its hardness and strength even at elevated temperatures.
- Resist thermal fatigue: The material should be capable of handling rapid temperature changes without any cracks or fractures forming in the cutting tool.
Lastly, I evaluate a cutting tool material’s affordability, since cost is an essential factor in any machining process. I take into account:
- Material cost: The cost of the cutting tool material should not exceed its performance benefits.
- Tool life: A longer tool life can offset a higher cost, as it reduces the frequency of tool replacements and maintenance downtime.
By carefully considering these factors, I can select the best cutting tool material for my specific machining requirements.
Applications and Industry Trends
In my experience, cutting tool materials are essential for various machining operations. They help improve productivity, reduce costs, and obtain better product quality. Some common machining operations are:
- Milling: Here, cutting tools remove material from the workpiece through rotary movement. High-speed steel (HSS) and carbide tools provide excellent performance in this operation.
- Turning: In this operation, I’ve observed single-point cutting tools remove material from the workpiece as it rotates. Common materials include ceramics, polycrystalline diamond (PCD), and carbide.
- Drilling: When drilling, a multi-point or single-point cutting tool is used to create cylindrical holes in the workpiece. HSS and carbide tools are my go-to choices for this operation.
I’ve noticed several emerging technologies shaping the cutting tool industry. These include:
- Additive Manufacturing: This technology enables the production of cutting tools with complex geometries, reducing material waste and production time.
- Coating Technologies: Advanced coatings, such as diamond-like carbon and nano-composite coatings, promise improved wear resistance, increased tool life, and better performance.
- Smart Tools: My experience with tools integrated with sensors and wireless connectivity shows potential for real-time monitoring and predictive maintenance, leading to reduced downtime and optimized tool usage.
By staying informed in these areas, industry professionals can make better decisions and maximize the efficiency of their cutting tools.