Fixing member with a recess at the end of its threaded shank

摘要

The fastener has a threaded end (10) whose face (12) contains a recess (14) into which a tool for tightening the fastener is inserted. The recess has a periphery (18) in the shape of a curved line forming three or more lobes. The ratio of the maximum distance from this line to the edge of the face and the corresponding minimum distance is 1.25 - 1.75.