Abstract: Apparatus is provided for welding studs to workpieces. The invention is particularly concerned with welding studs to workpieces made of materials having relatively low electrical resistance but covered with layers of other materials having higher electrical resistance, a common example being metal workpieces having painted surfaces. In order for the stud to make effective electrical contact with the workpiece at the beginning of the welding cycle, the paint must be eliminated; in accordance with the invention, this is accomplished by rotating the stud which effectively removes the portion of the paint in contact with the stud. Electrical contact can then be established between the stud and the workpiece to enable the welding cycle to be initiated.

Abstract: Apparatus for welding studs to workpieces by a drawn-arc welding technique is provided. The apparatus includes a stud welding tool having a plunge dampener mounted on the rear end thereof for dampening the plunge stroke of the stud during the welding cycle. The plunge dampener includes a rolling diaphragm which reduces friction. The plunge dampener also incorporates both vacuum and pressure for dampening the plunge stroke of the stud.

Abstract: A method and apparatus for welding studs to workpieces are provided. The invention is particularly concerned with welding studs to workpieces made of materials having relatively low electrical resistance but covered with layers of other materials having higher electrical resistance, a common example being metal workpieces having painted surfaces. In order for the stud to make effective electrical contact with the workpiece at the beginning of the welding cycle, the paint must be eliminated; in accordance with the invention, this is accomplished by rotating the stud which effectively removes the portion of the paint in contact with the stud. Electrical contact can then be established between the stud and the workpiece to enable the welding cycle to be initiated.

Abstract: The welding of studs by a drop technique is provided, including provisions for the rapid feeding of the studs to a chuck. In this type of welding, a stud is held a predetermined distance above a workpiece with an electrical potential established therebetween. The stud is held in a chuck which, in turn, is carried by a ram. The stud, the chuck, and the ram are allowed to drop the predetermined distance to the workpiece, at which time the stud becomes fused thereto. Weights are often applied to the ram and the distance of the stud above the workpiece can be varied to achieve a proper weld for a particular workpiece. Means are provided to rapidly supply studs to the chuck and include a chuck leg forming a loading passage and carrying the chuck at an end thereof. A feed passage communicates with the side of the loading passage and feeds studs thereinto from a remote supply source. A back-up plunger is affixed directly to the ram and extends into the loading passage of the chuck leg.