Self-locking threaded fastener and unlocking tool combination

A self-locking threaded fastener combination which includes a bolt assembly and a nut-like element comprising first and second threaded shank parts in end-to-end relation adapted to be conjointly threaded into said element, an axial keyway having a predetermined polygonal cross section extending through one shank part and at least partially through the other shank part, a key having a corresponding cross-sectional shape slidably received by said keyway for turning said shank parts in unison in said nut-like element, the adjacent ends of said shank parts having stepped end portions, each step including transverse surfaces, the transverse portions on the first shank part being connected by a pair of axially extending radial faces which if extended would join substantially on the axis of said first shank part, said radial faces forming an obtuse angle therebetween of less than 180.degree., said transverse portions on said second shank part being joined together by third and fourth axially extending radial faces which if extended would join substantially on the axis of the second shank part, said third and fourth radial faces forming an obtuse angle therebetween of less than 180.degree., the threads of said shank parts being continuous and aligned when the radial faces thereon are in predetermined spaced relation and said keyways in said shank parts are in alignment whereby said nut-like element may be threadingly rotated thereon in either direction, said nut-like element locking on the threads of said shank parts when said key is removed, said keyways are misaligned and said radial faces in relative positions other than in said predetermined spaced relation.