Diamond or CBN Grit with your Vitrified Grinding Wheel?

WHY USE A VITRIFIED GRINDING WHEEL

With a very hard and porous structure, vitrified grinding wheels are a popular choice amongst high productivity applications due to the great chip clearance and excellent coolant delivery. This type of grinding wheel has an extremely low wear rate and results in a high ratio of stock removal to wheel usage. The enhanced ability to dress a vitrified wheel allows for a larger layer depth with continual renewing of the grinding layer. The customization of this type of grinding wheels allows for the wheel to meet a wide range of customer applications, using either diamond or CBN as the abrasive. 

Compared to other product lines, the structure of a vitrified grinding wheel allows for no deflection as the wheel feeds into part. As the grit starts to take chips of material out of the part, the finished piece size is strongly controlled and an enhanced surface finish from any customer’s requirements. Vitrified wheels do not need to run as fast as other products in the industry and coupling that with the ability to flow coolant through the open structure, results in less heat generated and minimal thermal damage to the workpiece. 

REASONS FOR AND AGAINST DIAMOND GRIT TYPE 

With its exceptional hardness due to the symmetry of its structure, diamond seems the obvious choice for every grinding wheel operation. However, there are limitations on where diamond can be used in applications as it has a strong affinity for iron and hardened steel. Diamond is a pure crystal of pure carbon, and the carbon and iron molecules like to interact and bond when the heat is generated during a grind. As a result, this can potentially cause issues with the workpiece as well as increases the wear of the grinding wheel. 

ARGUMENTS FOR AND AGAINST CBN

In the application where diamond cannot be used, cubic boron nitride (CBN) is the next best alternative. The two big strengths are its ability to cut at extremely high temperatures and refusal to react with iron and other hardened steels when grinding. This makes CBN ideal when grinding tools and high-speed steels. The biggest downside to CBN is that the structure is not nearly as hard as diamond, and as a result, this grit type must run at a higher speed to be able to reach the same cutting abilities as a vitrified diamond grinding. Overall, both vitrified diamond & CBN wheels are available for a wide range of applications and can yield great results on a workpiece for a customer.