Fatigue life is defined as the resistance of the material to time variable or cyclic stress load. At a dynamic loaded component or a mechanical structure, incipient cracks appear after a certain number of load cycles usually starting from the surface of the structure. With further load cycles the cracks are growing until the remaining cross section breaks immediately. The fatigue life depends on the material, the type of load, mean stress, temperature, corrosion, dimension, stress gradient and surface properties. The surface properties in this context are surface integrity, residual stress and hardness. These properties are mainly influenced by the parameters of turning. In this diploma thesis a parametric study of the process parameters of turning is carried out regarding surface integrity and residual stress. The main parameters of turning are feed rate and tool nose radius. Based on experimental data, one simulation model is developed for surface integrity, and another for residual stress, depending on feed rate and tool nose radius. According to these results and including some principles of fracture mechanics a model for fatigue life of turned components is set up. This mathematical model is validated by a large number of fatigue life experiments. With this model it is possible to optimize the turning process in respect to fatigue life, by choosing the correct machining parameters without large financial expenses.