Gas metal arc spot welding is a variation of continuous GMAW, in which two pieces of sheet metal are fused together by penetrating entirely through one piece into the other. The process has been used for joining light-gauge materials, up to approximately 5
mm (3/16 in.) thick. No joint preparation is required other than cleaning the overlapping areas. Heavier sections can also be spot welded with this technique by drilling or punching a hole in the upper piece, through which the arc is directed for joining to the underlying piece. This is called a plug weld. A comparison between a gas metal arc spot weld and a resistance spot weld is shown in Figure G- 1.
