Abstract: Apparatus for mass producing locking patches of thermoplastic material on threaded portions of magnetic elements, such as screws. The apparatus includes a rotating dial assembly comprising a plurality of similar, closely-spaced permanent magnets, extending radially outwardly from the support thereof and completely thermally isolated from one another and on all sides except at a gap provided on its outer face. The screws to be patched are delivered to the periphery of the dial assembly where they are magnetically held by the magnets and carried past a heating station and a station where a stream of powder of the thermoplastic material is directed against preselected portions of the threads of the heated screws and fused in place to form the desired patches bonded to the unmodified threads of the screws.

Abstract: Disclosed herein is improved apparatus for mass producing locking patches of thermoplastic material on threaded portions of magnetic elements, such as screws. The apparatus includes a rotating dial assembly comprising a plurality of similar, closely-spaced permanent magnets, thermally isolated from one another. The screws to be patched are delivered to the periphery of the dial assembly where they are magnetically held by the magnets and carried past a heating station and a station where a stream of powder of the thermoplastic material is directed against preselected portions of the threads of the heated screws and fused in place to form the desired patches bonded to the unmodified threads of the screws.