Contributed by the Mechanisms and Robotics Committee for publication in the JOURNAL OF MECHANICAL DESIGN. Manuscript received March 2001. Associate Editor: J. S. Rastegar.

A review 1 of research on vibration and shock–induced loosening of threaded fasteners reveals a common thread throughout: the primary mechanism of self-loosening is relative slip within the threads and fastener nut or head interfaces. Such slip is caused by forces and moments which manifest themselves in joints through bending, pressure fluctuations, shocks, impacts, thermal expansion, and axial force fluctuations.

This work presents a locking fastener design that is an innovative variation of existing cam-type locking devices 2,3,4. This design replaces the inclined mating cams with counter-threads thereby eliminating the problem of bottoming out. In addition, this design utilizes a helical torsion spring to provide a controllable and adjustable amount of spring torque or moment to ensure if slip within...

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