A phenomenon in the beginning of cutting is classified rubbing region and ploughing region. In the rubbing region the deformation of bulk is elastic though tips of surface asperities are deformed plastically. It is obtained that the phenomenon is influenced by many foctors, especially by the tool-edge roundness.
In this study, in order to find the factors influencing the beginning phenomenon of cutting, an experiment was carried out on low speed orthogonal-cutting with a gradual increasing depth of cut.
As the results, there is a critical normal force which has a linear relation to the tool-edge roundness at the stage when the rubbing phenomenon changes into ploughing phenomenon, and the rubbing phenomenon is influenced by the machined surface layer of workpiece. Then, from the distribution of shear-stress, it is suggested that the transition to ploughing occures because the yielding of work-material developes in neighbourhood of the boundary region (the bulk and the surface layer).