Welding is the process of permanently joining two or more metal parts, by melting both materials. The molten materials quickly cool, and the two metals are permanently bonded. Spot welding and seam welding are two very popular methods used for sheet metal parts.
Spot welding is primarily used for joining parts that normally upto 3 mm (0.125 in) thickness.
Spot-weld diameters range from 3 mm to 12.5 mm (0.125 to 0.5 in) in diameter.