The frequency of dressing

A diamond tool ideally should not need any re-sharpening. The diamond-bond matrix consists of randomly dispersed diamond particles in a metal bond. As the diamond particles are worked on during the grinding operation, they wear off and lose their cutting faces by flattening off at the top exposed face, a phenomenon termed as glazing. However, the bond wear may not be at the same rate as the diamond wear. If the bond wear is faster than the diamond wear, the matrix is soft for the application, and the diamond tool is not suitable as it will give a low life. If the bond wear is slower than the diamond wear, the matrix is hard. This is most likely the case for glass grinding application. In this case the diamonds are not exposed enough to grind the glass at the required cutting parameters. Hence, a relatively soft abrasive such as aluminum oxide (AL2O3) is required to grind off the bond, and expose some new diamonds particles and re-expose the old ones. Some diamonds are also gorged out of the bond during this exposure. This is called dressing , sticking, or stoning.

Besides the differential wear rate between the diamond and the bond, there is always the possibility of glass fines suspended in the coolant system to cling on between the diamond particles. This also creates a situation of diamond under-exposure, which requires the use of an AL2O3 abrasive to remove the glass fines.

In both the above two cases, the AL2O3 abrasive, usually in the form of a stick, should not affect the diamond. A softer abrasive such as AL2O3 is used so that the diamonds do not get fractured further the grit size of the abrasive is one or two sizes finer than the mesh size of the diamond .This reduces the possibility of diamonds being gorged out of the bond during dressing.

The amount of AL2O3 stick used in dressing directly effects the grinding speed or the tool life of the wheel. Under the utilization of the stick will not re-expose the diamond properly, which will result in a loss of grinding speed. An over utilization of the stick will result in the loss of diamond due to gorging, and hence a loss of life.

Lower the frequency of dressing, better the diamond tool for the specific application.