Method of making self-locking fasteners

In a method of providing a threaded surface of an article with a self-locking element comprising an adhered body of normally hard, tough, resilient resin including the steps of heating the threaded surface to a temperature above the softening point of said resin, thereafter directing a stream of fine particles of said resin to a selected area of said threaded surface while said threaded surface is at a temperature above said softening point, catching resin particles from said stream by softening them and causing them to be held on said threaded surface and to melt to a continuous resin body extending smoothly between generally axially extended edges of said area by heat from said threaded surface and solidifying said resin body, the improvement which comprises applying said resin particles in a plurality of spaced successive streams, controlling the rate at which and time during which resin particles of a first stream are directed to said threaded surface to form a deposit of a first portion of resin particles held on said threaded surface by heat softened resin and with exposed portions of said deposit retaining particulate character, said deposit of resin being in amount less than that desired in the self-locking element, maintaining said threaded surface at a temperature above said softening point for a time after completing deposition of said first portion of resin particles determined relative to the quantity and melting characteristics of the resin particles substantially completely to melt the deposited first portion of resin, thereafter directing a further stream of resin particles at the molten resin deposit where the particles are caught up and held by said molten resin to build up the quantity of resin on said threaded surface, coalescing the deposited resin to a substantially continuous body of resin extending smoothly between generally axially extending edges and cooling said body of resin to harden it to a solid body resistant to displacement and effective to give a locking action when a complementary threaded surface is assembled with said threaded surface.