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Grinding wheels must make proof of a minimum fracture strength in order to ensure safe grinding processes. In this context the most important characteristic is the bursting speed which is determined in spin-burst tests. Grinding wheels with phenolic bond as a typical example for resin-bonded wheels were used to investigate relations between wheel structure and bursting speed. The tests showed that the bursting speed rises with increasing grain and bonding volume and with finer abrasive grain size. The bursting speed also depends on the type of abrasive, aluminium oxide or silicon carbide. Furthermore, the material characteristics elastic modules and bending strength were determined. In contrast to the elastic modules the bending strength correlated with the bursting speed. The bending strength can be used to calculate the bursting speed retrospectively from wheel fragments, for example within 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. |