The aim of research of the tribological conditions in the tool-workpiece interface in cutting processes is to find the main causes for unpredicted tool life. As it is shown in the paper there are many causes for their influences on the tool wear. Not only mechanical and chemical but also thermochemical aspects of wear is important. The high cutting temperature, which is a result of high-speed cutting (HSC), enhances diffusion and oxidation process. Diffusion processes between the chip and the top rake surface of the cutting edge result in crater wear, and oxidation reactions with the environment induce scaling of the cutting edge. The phenomenon of central wear can be used to define the tool life in the case of HSC milling of alloyed tool steels (hardness > 45 HRC).