Based on the results of dislocation analysis at the substructure level, a new physical interpretation of the process of cutting materials as their controlled destruction with previous plastic deformation is proposed. From a single physical point of view, the main questions of the theory of cutting are considered: the reaction of the processed and tool materials, the formation of the properties of the surface layer of the part, machinability by cutting, methods of intensification, as well as deterministic and stochastic optimization.