An Analysis of the Mechanism of Orthogonal Cutting

Abstract

The orthogonal cutting mechanism with the transitional deformation range (i.e the “flow region” which exists between the rigid region of workpiece and the plastic region of steady chip), instead of the conventional shear plane, is analyzed theoretically in the case in which simple continuous chip is produced under the assumption of a perfectly plastic solid. Using the results, the experimental data for lead and brass are discussed. The theoretical expressions derived thereby can be reasonably applied to a wide range of cutting conditions, and also to the cases associated with quasi-continuous and discontinuous types of chip without any contradiction. In all cases the starting boundary-line of flow region is situated under the conventional shear line, and the ending boundary-line above it. The inclination angles of both boundary-lines and the sector angle of flow region increase with rake angle. With an increase of depth of cut, the inclination angle of starting boundary-line increases, while that of ending boundary-line and, hence, the sector angle increase for lead, but decrease for brass. Furthermore, the strain of chip based on the cutting state with a flow region is much smaller than the conventional shear strain based on the cutting state with a single shear plane. The strain of chip decreases with an increase of rake angle, and it has a tendency to decrease slightly for lead and increase gradually for brass with an increase of depth of cut.