Abstract: A method of applying a coating, such as a fluorocarbon barrier coating, to the threads of a fastener, particularly suitable for applying a coating to a female fastener having a threaded bore. The method includes forming a fluid suspension of the coating material, such as an unpolymerized fluorocarbon in an organic solvent, forming a drop of the coating material fluid suspension on the tip of an ultrasonic transducer and bringing the tip into proximity with the fastener threads, which are preferably preheated. The ultrasonic tip is then vibrated in the ultrasonic range, exploding the drop and coating the fastener threads with a fine mist of the fluid suspension. The fastener is then heated to vaporize the solvent and polymerize the coating material where the coating material is polymerizable. When coating female fasteners, the tip of the ultrasonic transducer is preferably lowered within the thread cylinder, adjacent the top thread.

Abstract: A rotary workpiece treating apparatus is described particularly useful for depositing coating or adhesive materials within threaded fastener nuts. The device includes a continuously rotating turntable assembly having a plurality of workstation cylinders attached thereto. Installed within the cylinders are plungers having cam followers, which plungers move between a first and second position as the turntable assembly is rotated. A probe attached to the plunger is caused to enter within the internal bore of the nuts and release flowable material within the nut. The flow of such material is controlled by a valve stem protruding from the probe which is depressed against a stop surface when the probe is inserted within the nuts. A second clamping plunger within the cylinder clamps against the nut when the probe is being inserted, thereby positioning the nut and preventing flowable material from being deposited on the exterior surfaces of the nuts.