The use of diamond tools has increased enormously in recent decades. However the wear process during the cutting operation of the diamond tool has not been properly investigated and is poorly understood. The cutting performance of a diamond tool is strongly influenced by the wearing process. The principal factors that require consideration in predicting wear rates are the composition of diamond tool, the operating parameters and the characteristics of the material being cut. The work described in this paper involves an investigation of the wear processes of diamond tools in order to predict the cutting performance in a given operation. A series of tests and simulations were carried out in order to try to understand the cutting action and mode of wear on the diamond tools and to evaluate which properties influence the operation. A mathematical characterisation of the performance of a diamond tool for specific conditions was proposed which would be valuable technically and economically to diamond tool manufacturers and users.