As a rule of thumb, the following principles can help in choosing the right material:
♦ For hard materials, it is recommended to use a soft-bonded cutting wheel
♦ For medium hardness materials, it is recommended to use a medium hardness bonded cutting wheel
♦ Hard bonded cutting wheels are recommended for soft materials
Most manufacturers specify a manufacturing date or a best before date for their cutting wheels. These dates must be observed because the epoxy resins of the binder are hygroscopic, that is, they absorb moisture. Moisture in the binder can cause the cut-off wheel to become brittle after months or years. In this case, the cut-off wheel can still be used, but its wear will increase significantly and the risk of chipping will also increase significantly.
For very ductile materials such as titanium or plastics, cutting wheels with silicon carbide abrasive grains (also resin bonded) are often used. Diamond cut-off wheels are suitable for very hard materials (ceramics, glass fiber reinforced plastics, minerals, glass, etc.). Two different bond types are available: metal-bonded cut-off wheels, where the diamonds are usually embedded in a bronze bond, or those with a synthetic resin bond. The latter are particularly suitable for cutting very brittle materials.
Compared to saw blades, cutting wheels produce a smoother and less deformed surface and abrupt contact in and out of the sample position, which significantly reduces the thickness of the deformed layer that must be removed by subsequent metallographic grinding.
