Tool steel hardness determines the durability of tool steels at the rate they wear during processing. The hardness varies depending on the microscopic crystal structure in the internal structure of the tool steel and the loading of the steel material during machining. Tool steels are produced with a mixture of elements such as carbon, silicon, manganese, phosphorus and copper, and the mixture of these elements determines the hardness.
The hardness of tool steels is measured by standard test methods such as the Rockwell hardness test. The hardness of tool steels is measured on the Rockwell C scale (RC) and is generally rated in the 60-65 RC range. However, higher or lower hardness tool steels can also be used, depending on the nature of the material to be machined, the way it is processed and the intended results.