An advantage of spot welding is it only a few seconds for a sound weld. Because the heat is confined to a small area (the ¼" diameter electrode), warping and distortion is easily avoidable. It also allows for accurate control that lets you make consistently uniform welds.
Become a pro in just a few minutes. Hook the spot weld gun to the electrode holder of your arc welder (50 amp or less) and ground to car body. Just pull back the trigger to retract electrode, line up weld point, and press against the metal. (Note: Metal must be free of paint, rust, or grease). Release the trigger and allow the electrode to contact the metal and glow for one to two seconds. Then raise the electrode with the trigger and allow an arc to form a molten puddle of metal (always use welding goggles or shield).
Each weld takes about 5-6 seconds.
Automotive manufacturers used spot welds to build your car and you can restore it with the same technique.
-Courtesy of Eastwood.com