Locking fastener

In a locking threaded fastener of the type comprising a threaded shank with threads advancing axially of the shank in a tightening direction from an outer end to an inner end, and a nut assemblage including a first nut member having outer and inner faces and having a through-hole for a clearance fit with the threaded shank and including a second nut member having outer and inner faces and having a threaded hole for threaded engagement with the threaded shank, the second nut member being disposed nearer the outer end of the threaded shank than the first nut member whereby a workpiece surface may be disposed between the first nut member and the inner end of the threaded shank, said nut members having facing surfaces with a wedge cam formed on the facing surfaces for coupling the first and second nut members together for rotation together when the second nut member is rotated in the tightening direction and for wedging the first and second nut member axially apart in response to rotation of the second nut member relative to the shank and the first nut member in the loosening direction, the wedge cam having a wedge angle which is greater than the angle of the threads whereby such rotation causes the threads to jam and inhibit loosening of the second nut member, the improvement in said nut assemblage wherein:

• said first nut member has a flat inner surface for engaging a workpiece surface with frictional resistance between said inner surface and said workpiece surface,
• and said wedge cam has engaging surfaces with frictional resistance therebetween which is less than the frictional resistance between said flat inner surface and the workpiece surface.