Cutting Forces in Hard Turning Comprising Tool Flank Wear and Its Implication for the Friction between Tool and Workpiece

Original scientific paper In this paper, the orthogonal cutting force model is proposed comprising forces due to flank wear in addition to the forces for chip formation during the hard turning of round bar made of steel 60WCrV7 hardened at 55+2HRc. Cutting force model includes two tool conditions: perfectly sharp tool with VBB = 0 and tool with maximum permissible flank wear VBBmax. Based on cutting force measurements and established force relationships between the wear forces and forces for chip formation, it is possible to analytically predict the friction coefficient between the tool and workpiece. From pure geometrical relationships between forces the equation for the friction angle between the tool flank and workpiece can be derived. The friction coefficient at the toolworkpiece interface was measured using block-on-the-disc tribometer. Predictions of the friction coefficient by means of established mathematical model are compared with experimental results, and overall a good agreement is observed.