The friction at the cutting wedge has a significant influence on tool wear. Due to the strong local variance of temperatures and stresses at the cutting wedge, the friction conditions differ significantly locally. In this work, a method is presented with which normal stress es, tangential stresses and local friction coefficients at the cutting wedge can be determined based on experimental investigations. For this purpose, high-speed recordings and force measurements are conducted on a planing test rig. In addition to dry cutting processes, investigations are carried out on the test rig using emulsion and oil as metal working fluid. The results show a reduction of the coefficients of friction when oil is used as metal working fluid. However, when emulsion is used as metal working fluid, the coefficient of friction changes only slightly compared to dry machining. This can be attributed to low film-forming ability of the emulsion.