Strength of grinding wheels with resinoid bond

Grinding wheels must make proof of a minimum fracture strength in order to ensure safe grinding processes. In this context the most important characte ristic is the bursting speed which is determined in spin-burst tests. Grind ing wheels with phenolic bond as a typical example for resin-bonded wheels were used to investigate relations between wheel structure and bursting spe ed. The tests showed that the bursting speed rises with increasing grain an d bonding volume and with finer abrasive grain size. The bursting speed als o depends on the type of abrasive, aluminium oxide or silicon carbide. Furt hermore, the material characteristics elastic modulus and bending strength were determined. In contrast to the elastic modulus the bending strength co rrelated with the bursting speed. The bending strength can be used to calcu late the bursting speed retrospectively from wheel fragments, for example w ithin the framework of failure or accident investigations. Long-term tests in damp alternating atmosphere showed that moisture can reduce the strength of resin-bonded grinding wheels. The moisture resistance, however, can be improved by pretreating the abrasives with adherence agents, e.g. silanes.