During the last decade in the EU the usage of biomass for energy purposes has been significantly increased. Extremely wide application of biomass produced by wood production as well as wood processing is taking place (COST Action FP 0902). Cutting the wood is realized by powerful machines with cutting knives made of high quality wearing out resistant steel with hardness HRC 55-59. In order to investigate the wood cutting process it is necessary to study the process of taking off the edge (wearing out) of the tool, taking place during the cutting (1, 3). As a whole the wearing out of the cutting knives is a combination or a sequence of concrete physical processes having mechanic, heating, electric and mechanic-chemical origin. The taking off the edge is realized in their cutting part being in contact with the material processed. Immediate influence on knives’ wearing out resistance realizes the volume of the material processed. In the zone of the edge there is high concentration of mechanic energy and as a result high pressure is formed, meanwhile significant tensions in the cutting part of the tool. The higher the energy concentration in this zone the higher the destruction of the material processed. This is one of the mechanisms for better management of the cutting process and for the improving the quality of the material.