Mechanics of machining with chamfered tools

Chamfered cutting tools are used in high speed machining of hardened steels due to their wedge strength. An analytic model is proposed to investigate the influence of chamfer angle and cutting conditions on the cutting forces and temperature. The model is based on the tool geometry, cutting conditions, steady state temperature in the shear and chip-rake face contact zones, strain, strain rate, and the corresponding flow stress of the work material. With the aid of a slip line field model, the cutting and friction energy in the primary, secondary and chamfer zones are evaluated. By applying the minimum energy principle to total energy, the shear angle in the primary deformation zone is estimated. The corresponding shear strain, strain rate and flow stresses are identified. The model leads to the prediction of cutting forces and temperature produced in three deformation zones. The model is experimentally verified by high-speed orthogonal cutting tests applied to P20 mold steel using ISO S10 carbide and CBN cutting tools. It is shown that the analytic model is quite useful in selecting optimal chamfer angle and cutting speed which gives the minimum tool wear and relatively lower cutting forces.

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