Abstract: The method of making a screw connection includes measuring a torque applied to the screw by a controllable screw driver device and measuring a rotation angle of the screw in individual connection steps during the making of the connection to obtain measured values of the torque and rotation angle; calculating a change in torque over a predetermined rotation angle interval from the measured values and deriving a stiffness parameter from the change in torque divided by the rotation angle interval; calculating a change in rotation angle over a predetermined time interval from measured values of the rotation angle and predetermined time interval and deriving a rotation speed as the rotation angle change divided by the predetermined time interval; analyzing the stiffness parameter and the rotation speed by a fuzzy-logic device to obtain controlling output variables and operating the fuzzy-logic device in one of three operating modes to obtain the controlling output variables and to produce at least one adjusting pa

Abstract: A method for tightening a screw utilizes a power-impact or pulse driver. The prestressing force in the screw to be tightened is increased step-by-step during the tightening operation and evaluated. By detecting the prestressing force in the screw on a step-by-step basis, the step heights pertaining to the increase in the prestressing force and the change in the step heights are used as criteria for the screw-coupling quality and for controlling the screw-coupling operation. In the same way, the number of impacts or pulses is also used as a criterion for the screw-coupling quality and for controlling the screw-coupling operation.