The standard describes methods for process capability tests (PFU) for the prevail torque of screw joints with preload force. The goal of process capability tests for screw joints is the assessment and documentation of the quality capability of a bolting process under production conditions. Process capability tests provide criteria for assessment and continuous improvement of the bolting process under production conditions. These include identification of systematic influences for the targeted improvement of the bolting process; assessing the impact of measures for process improvement; assessing the tolerances for process capability tests; setting the control limits of control charts. Unlike machine capability tests (MFU), in addition to the machines influence, the impact categories human, material, method and contemporaries (environment) are considered in the process capability test.