This study of the mechanics of grinding used a single grit approach and involved the development of a high frequency dynamometer to measure grinding forces at speeds of up to 37 m s −1. Experiments have been carried out using idealised cutters to simulate abrasive grits; the grinding forces, the grinding coefficient and the specific energy were measured for a wide range of cutting speeds and workpiece hardness. For a grit of a given geometry the main factors affecting efficiency were found to be the hardness of the workpiece and the cutting speed. A theoretical model of the grinding process has been developed which enables normal grinding forces to be predicted from the flow pressure of the workpiece and the geometry and cutting efficiency of the grit. The implications of the work are discussed with particular reference to surface finish.