Abstract: A power wrench in which an output shaft is powered by a motor via a magnetic torque responsive release clutch, and in which a torque non-responsive clutch is connected between the release clutch and the output shaft. Cam teeth which are associated with the release clutch halves are effective to inactivate the torque non-responsive clutch as the driving and driven halves of the latter, during increased torque load, have reached their fully released position. As the release clutch is unloaded there is an angular gap between the cam teeth corresponding to the relative angular displacement arising between the release clutch halves as the load on the release clutch is increased from zero to release level.