Its common to use metric steel bolts for power train components in the car industry. Since the VDI2230 standard isnt appropriate for light alloy metals experience and long time knowledge is a common practice to design a fasteners. Power train components are high loaded, the relaxation of the fastener due to the temperature load is very important for the fastener functionality. There is no correlation between the forming torque and clamp load of self tapping bolts. The work is dealing with an mathematic approach to calculate the clamp load due to the forming torque.