Applications include attachment of reinforcing braces and stiffeners, functional brackets, hinges and other parts. Often, spot welding is the method of choice for assembly of entire enclosures, cabinets and multipart assemblies. Thickness of the majority of parts joined by spot welding ranges up to 1/8 in. (3 mm) for each member, although parts up to 1/4 in. (6 mm) thick have been successfully spot welded. Based on the experience of stampers and fabricators, certain general recommendations can facilitate spot welding of a sheet metal design, no matter what metalforming process is used to make it. It is always useful to consult with the metalformer in the design stage when questions arise regarding the part design, application of spot welding or, control of spot welding cost for a particular design.

If the sheets are the same thickness then the power setting used for plug welding would be the same as you would use for 1.5 times the thickness of one of the sheets. This is the sort of penetration you would expect from a plug weld. The molten pool is just breaking out of the reverse of the back sheet. The heat marks indicate the weld has arced against the back sheet rather than at the side of the hole. If you don’t get these marks then consider a little seam welding just to be sure. There is a special clamp designed for plug welding that makes life really easy. The parts you see in the photograph are attached to a normal mole grip. This clamp came in a set of three random welding clamps all of which are extremely useful.

How Does Spot Welding Work? A form of resistance welding, spot welding is one of the oldest welding processes whereby two or more sheets of metal are welded together without the use of any filler material. The process involves applying pressure and heat to the weld area using shaped alloy copper electrodes which convey an electrical current through the weld pieces. The material melts, fusing the parts together at which point the current is turned off, pressure from the electrodes is maintained and the molten “nugget” solidifies to form the joint. See more info on Spot Welder.

In the same category you also find generators, always operating on direct current, intended for car bodywork including repairing dented panels. The machine consists of a holder which lets you position your welding gear precisely in front of the deformed zone, and uses mechanical or hydraulic force to restore it to its original shape. All you have to do is crack out your hammer to fine-tune the finish. The “gougeonneuse”, as it’s known in France, can be used to mend tow rings and other specific parts. The huge advantage of being able to return a panel or component to its original shape without needing to disassemble the car body makes this machine a must-have tool for bodywork!