Abstract: A mobile friction welding machine is provided for creating friction weld joints in workpieces such as metal sheets, especially lead sheets is described. The machine has a track assembly to guide it across work pieces, including a caterpillar track system on the machine. The friction welding is achieved by rotating a probe and applying a downward load on the probe to urge it into the work process. The probe is preferably a pair of spaced apart probes having a crescent-shaped cross-section.

Abstract: A method of operating on a workpiece comprises offering a probe of material harder than the workpiece material to a continuous surface of the workpiece causing relative cyclic movement between the probe and the workpiece while urging the probe and workpiece together whereby frictional heat is generated as the probe enters the workpiece so as to create a plasticized region in the workpiece material around the probe, stopping the relative cyclic movement, and allowing the plasticized material to solidify around the probe. This technique, which we refer to as "friction plunge welding" provides a very simple method of joining a probe to a workpiece. The method can be used for repairing cracks and the like within a workpiece or for joining members, such as studs or bushes, to a workpiece.