View Full Version : Butt welding questions


05-04-2006, 09:40 PM
I am doing some sheetmetal replacement on my Mustang and I'm having some welding issues. I'm a better than decent welder but each time I weld a spot with the MIG the weld rises in the middle (sort of like an elf's hat) and then the weld has a hole in it when ground down. I've dabbled with wire speed and heat, but I can't find a setting that will consistently not do this. What causes this?

After repeatedly filling the holes from the first problem, I ground down the weld flush with both panels. However, when I finished, one side of the weld was raised higher than the weld and the other side. I was very careful to be certain that both panels were flush when I started (I used panel clamps about 3 inches apart), but the high side was the reproduction sheetmetal (thinner). I'm moving from one area to another for each weld and cooling the metal with a wet rag, so I don't think I overheated the metal. What did I do wrong?

As for bodywork, I guess I'll need to hammer the ridge down so I can skim it with filler. Do I use the pointed body hammer for that, or do I use a flat hammer and a dolly behind it (at least the part I can reach)?

John Kelly
05-05-2006, 07:33 AM
Sounds like your shielding gas is not covering the weld. Check the cup nozzle for spatter build up that could be blocking the flow of gas. Or, try adjusting the gas flow up. If you are using flux core, the wire might be bad?

I would hammer and dolly the two levels of sheet metal back together to make them as flush as possible. If it is difficult, try a little heat from a torch to soften up the weld first. Not red hot, or blue hot..something below that. There should be no need to quench welds. You risk hardening the metal and locking in the shrink from welding. No science to back this up, just my observation. After grinding the metal flush on both sides (where possible) hammer and dolly the weld to stretch it back out a little bit. Here is an article that might help you:


John www.ghiaspecialties.com

05-10-2006, 12:16 PM
Like John said, either the sheilding gas isn't on or something with it, or you have dirty metal. Remember, even the back side of the metal has to be clean. When the metal melts, it pulls the contaiminants up from the rear.


10-15-2006, 12:12 PM
I'm no expert, but I've had that problem before and what was happening to me was the welder was too hot and burnt a hole completely through the lower panel. While the center of the weld was still molten it dropped out from under the weld. This left a sort of cavity in the middle of the weld and the "elf's hat'' effect you were talking about. I could hit the spot with a hammer and collapse it . I turned the heat down a little and it quit. I also found that not holding the spot for quite as long helps too.

10-17-2006, 02:58 PM
[QUOTE=jmoffett]I am doing some sheetmetal replacement on my Mustang and I'm having some welding issues. I'm a better than decent welder but.

I envy all who really know how to weld but, I found a way to eliminate alot of problems the not-so professional welder, ( me ), encounters. I do the same weld with scrap pieces of the same sheet metal on the bench to get my settings and technique together before I do the actual work on the car. It's not always the fastest way to go about things, but the work on the car comes out like I know what I am doing. I trash alot of scrap metal instead of the job.