Yes, novices can weld and repair sheetmetal with plenty of patience and attention to detail
Sheetmetal fabrication and replacement mystifies a lot of us because it takes talent and patience to achieve the desired results. It also takes experience. However, every skill we learn has to start somewhere, and panel replacement is something you can learn both by doing and by watching others who know how to do it well. We’re going to illustrate how to patch and replace panels yourself in your home garage. To get there, you’re going to have to invest in, or rent, tools to do the job.
Right off the top is a big one: You’re going to need a light-duty wire-feed MIG welder, which will enable you to stitch and “rosette” weld (also known as plug welding) sheetmetal components using household current. You’re also going to need the tools of sheetmetal repair, and that list can get lengthy—a grinder with a variety of discs, body hammers and dollies, aviation snips, clamps of various types, a 1/2-inch drill and drill index, and a variety of putty knives and spreaders with which to apply filler. Don’t forget eye and face shields along with work gloves to protect your hands. Of course, you’re bound to discover more needs as you go to work.
If you’re replacing entire body panels, it is strongly suggested you stick with the factory seams and avoid creating new “butt joints,” where the ends of two pieces of sheetmetal are butted together and welded. Although this is common practice for body technicians, it takes a lot of skill and experience to know how to successfully conceal a butt joint and to make sure it won’t reveal itself later. For the novice, butt joints can create problems later on, especially if they can be seen in the paint. Overlapping of the welded joints can be easier to execute during the welding phase, but this will usually require more filler work afterwards to conceal, which may also result in problems later.
Still, there are likely to be situations where a butt joint is unavoidable, as when using a steel patch panel. Patience is required —if you’re hurrying and get the metal too hot, the result will be excessive distortion (waviness) of the metal, necessitating more bodywork later, likely requiring more filler. It is best to “touch” or “stitch” weld to join the two pieces to achieve the initial bond. Then, you can go back and fill between the welds. This technique should help you achieve a better joint with minimal— or no — distortion.
Most car bodies were spot-welded together at the factory to begin with. Spot welding is a type of electrical resistance welding that joins two or more pieces of steel between two clamping electrodes —it yields a weld at the “spot” where the two electrodes pinch the pieces of metal together. When the electrodes are electrified, the resistance between them briefly creates heat so extreme that the pieces of metal fuse together in a molten puddle and the material of the adjoining pieces of metal melt together. The spot welds are around 5⁄16- to 3⁄8-inch in diameter.
Dashboard Patch Job
When you separate and replace panels at the factory seams, you can use a spot welder, or you can use the aforementioned rosette/plug weld technique. With this approach, 1/4-inch to 1/2-inch holes are drilled along the seams of the replacement panel, and then the two adjoining panels are clamped together. The holes are then welded with a wire-feed MIG welder around the perimeter of the holes until they are filled. Once welding is complete, each weld is finished with a grinder to smooth the rosette weld. This can be done so that the welds disappear (some filler work may be needed for this), or you can simulate factory spot welds by using a center punch after grinding the rosette weld.