Why Diamonds Aren't Used for Cutting Tools
When it comes to cutting tools, tungsten carbide and other materials like cubic boron nitride (CBN) and silicon carbide are commonly used. However, many wonder why diamonds, which are among the hardest known materials, aren't used in cutting tools. This article explores the reasons behind this choice.
The Role of Tungsten Carbide in Cutting Tools
Tungsten carbide is a preferred material for cutting tool inserts due to its unique properties. It can be compounded with a cobalt binder to form larger shapes and can be coated with harder, more wear-resistant materials, such as titanium nitride or diamond. This versatility allows for the creation of durable and effective cutting tools.
While tungsten carbide is not a metal in the traditional sense, it is still categorized as a ceramic. When compounded with cobalt and coated with other materials, it forms a metal matrix composite. This makes it suitable for a wide range of cutting applications without the need for large diamond crystals.
The Challenges of Using Diamonds in Cutting Tools
The primary reason diamonds are not extensively used in cutting tools is their high cost and difficulty in shaping. Small diamond crystals can be produced easily and affordably, but creating large, pristine crystals is a complex and expensive process. Moreover, the hardness of diamonds makes them challenging to shape into the required cutting tool shapes.
Even if diamonds could be shaped and utilized in cutting tools, the cost would be prohibitive for most applications. In woodworking and other small shop settings, the ROI (Return on Investment) often takes years, making diamond cutting tools less justifiable financially.
The Chemistry of Diamond and Metal Interaction
A significant factor in why diamonds are not used for cutting tools in machining operations, especially for ferrous metals, is the chemical interaction between diamond and iron. Pure diamond is around 99.9 percent carbon, while steel is mostly composed of iron and carbon. High temperatures and pressures during machining cause the iron to absorb carbon from the diamond, leading to rapid tool dulling.
On the other hand, tungsten carbide and ceramic materials are far more resistant to this chemical interaction. They can effectively cut any metal alloy without the same drawbacks as diamond. Silicon carbide, for example, is a popular alternative often used in shaping and sharpening cutting tools.
Special Applications and Future Possibilities
Despite these challenges, diamonds do find use in specific applications. They are commonly used for grinding disks and in special situations where high hardness and wear resistance are required. Engineers are continuously exploring ways to improve the manufacturing process of synthetic diamonds to make them more accessible and cost-effective for cutting tool applications.
With advancements in technology, it is possible that synthetic diamonds could one day replace some of the uses of tungsten carbide in cutting tools. However, for now, tungsten carbide remains the material of choice for most applications due to its cost-effectiveness and practicality.
Conclusion
While diamonds are an incredibly hard material, their practical uses in cutting tools are limited by their high cost and the challenges in producing and shaping them. Tungsten carbide, with its unique properties and cost-effectiveness, remains the go-to material for most cutting tool applications. As technology advances, we may see more opportunities for diamonds in cutting tool applications, but for now, tungsten carbide and its alternatives continue to dominate the market.