The methods of machining of hardened automotive steel components are undergoing a rapid development. In a great number of cases, conventional grinding is substituted by new turning methods that are cheaper and/or faster compared to grinding. During machining of case hardened steel the surface of the work piece is influenced plastically, thermally and chemically. The normal force applied on the work piece by the machining tool causes plastic deformation giving rise to residual compressive stresses at the surface layer of machined components. Friction between the tool and the work piece results in heat development leading to residual tensile stresses at the surface layer. The tensile stresses are detrimental for the fatigue behaviour of case hardened parts such as gears. They promote fatigue crack initiation and accelerate crack propagation. In industrial production it is essential to choose suitable machining parameters to reduce the heat flow into the work piece. Since the wear of the tool increases the development of friction heat, a critical number of machined components has to be determined for which the residual stress state is satisfactory. Excessive heat development during machining will cause tempering or rehardening of the surface layer, so called grinding burns. In this paper, examples of residual stress and peak width distributions are presented. X-ray diffraction measurements were performed on case hardened components machined by grinding, honing, turning and plunging.