In-process measurement of friction coefficient in orthogonal cutting

In order to represent actual cutting process conditions, an in-process tribometer is examined to measure friction during orthogonal turning process at cutting speeds up to 300 m/min. The tribometer consists of a spring preloaded tungsten carbide pin with spherical tip mounted behind the cutting edge and rubbing on the freshly generated workpiece surface. The pin preload is set according to feed force. A 3D-force measuring device in the fixation of the pin allows evaluating friction coefficient from tangential and normal forces. Experiments show strongly different results when contacting fresh and oxidized surfaces and decreasing friction coefficient with increasing cutting speed.