This paper shows the results of investigations performed in the brittle materials microcutting at the Faculty of Mechanical Engineering, Belgrade University. The interactions between a single diamond grain and the machined granite are analyzed. The change in the normal cutting force as a function of grain penetration speed and depth was experimentally established in microcutting of two types of granite originating from Serbia. Based on the grain traces on granite and the generated cracks, the critical grain penetration depth for the formation of brittle fracturing was established. The experiments are intended to assist in the optimization of the grinding process as technology dominant in the granite finishing.