Controlled-torque fastener

摘要

A controlled-torque fastener limits the torque which may be applied to it for the delivery (screwing-in) of the fastener into a threaded bore of a workpiece or the like. The fastener has a threaded shaft and a tool seat which is configured to be engaged by a driving tool such as a conventional wrench. The tool seat is movable between a driving position in which the tool seat is in driving engagement with the shaft and a non-driving position in which the tool seat effectively disengages the driving tool from driving engagement with the shaft. Resilient biasing means urge the tool seat into the driving position, and driving torque applied to the tool seat urges the tool seat against the biasing force towards the non-driving position. When the driving torque applied to the tool seat exceeds a pre-selected maximum torque, the biasing force is overcome, thereby disengaging the driving tool from effective driving engagement with the shaft, and discontinuing delivery of the fastener.