It seems as if the abrasive grains are working in a free movement which is not entirely true. Depending on the lapping process used, the abrasives are either freely rolling or sliding between the workpiece and lapping plate. In diamond lapping, the abrasive particles become fixed within the machined medium. The material removal takes place slowly due to the movement of the lapping plate with respect to the workpiece. http://www.szjiuyuda.com/lapping-machine/flat-lapping-machine/