Friction quantification in the oblique cutting with CBN chamfered tools

This paper develops a new analytical-empirical model of friction for oblique cutting which considers the influence of the inclination angle or/and relevant variations of the rake angle caused by the tool wear. The novelty of this concept is the introduction of the equivalent rake face and the corresponding equivalent rake angle. New techniques for determining the equivalent rake angle using the force equilibrium and the recorded profiles of the worn part of the chamfered tools are proposed. The computation procedure includes converting the three measured components of the resultant cutting force into the lmn coordinate system which projects the componential forces on the rake face. As a result, the friction coefficient is calculated using computed friction and normal forces and equivalent rake angles. It was documented that the obtained values of the equivalent friction coefficient differ distinctly from those computed for classical orthogonal or oblique cutting with a small inclination angle. The new friction model was tested for the machining of spheroidal cast iron using CBN chamfered tools, although the procedure has a universal character.