272,807. Klafke, A. Feb. 4, 1927. Locking nuts.-A nut or bolt-head having an undercut annular groove d with conical surfaces f, g is associated with a washer g on which is an upturned collar, divided into sections c<1>, c<2>, constructed to enter the groove d. The nut may have a bevelled surface s which forces alternate sections c<2> into the bolt-threads, the sections c<4> being bevelled on the inside, and the shorter sections c<1> on the outside. The wall f of the groove d may be slotted to increase the pressure of the nut on the bolt. The washer has tongues t or punched-out projections for engaging the work. Slots e, Fig. 11, in the wall g of the groove are arranged non-symmetrically in respect of the sections c<1>, c<2> so that one of the sections may be forced into one slot. In a modification for rail bolts the washer is rectangular and is bent down at opposite sides r, Fig. 22, to enclose a helical spring washer u. The washer b has slots v and tongues m for holding the spring washer. In a further modification the washer has a single flange r, Fig. 17, reinforced bv ribs y which engages the flange of the rail and may be bent under it.