Apparatus and method for selectively applying powder coatings onto internally threaded fasteners

Abstract

An apparatus for applying a thermoplastic powder to internal threads of a fastener includes a vacuum nozzle having an end adapted to engage a first surface of the fastener. A spray tube is sized to be inserted within the bore of the fastener and communicates with a source or sources of thermoplastic powder and pressurized air. A bushing is mounted on the spray tube so that the spray tube is able to slide with respect to the bushing. The bushing is adapted to engage a second surface of the fastener. The spray tube and bushing are movable between clamping positions, where the vacuum nozzle and the bushing engage the first and second surfaces of the fastener, and release positions where the vacuum nozzle and the bushing do not engage the first and second surfaces of the fastener. A fastener holder holds the fastener between the vacuum nozzle and the bushing so that when the vacuum nozzle and the bushing are in the clamping positions, the spray tube enters the bore of the fastener and sprays thermoplastic powder on the internal threads of the fastener with excess thermoplastic powder collected by the vacuum nozzle. The vacuum nozzle and bushing may be machined and to permit either, both or neither of first and second chamfers of the fasteners to also be coated.