I'm in the process of restoring my 1973 duster and have a fender that has rust. I found a donor fender and I'm using a Lincoln SP-125 plus wire feed welder with gas to patch the pieces together.
Does anyone have any tips on how to butt weld the metal together well enough so that you can grind off the weld and the parts stay together? I'm having a tough time getting penetration completely through the fender. I either blow through the metal or barley tack through the surface so that when you grind off the weld it easily brakes apart? Any help with wire speed and heat setting /techniques/ or self help videos would really be appreciated.

Brad  

To start make sure all the surfaces are clean. A grinder with 36 to 80 grit will work fine. When butt welding you want a slight gap (patch panel smaller then hole being filled) between the parent metal (fender) & your patch. Your gap should be about the thickness of the metal your working with. Your patch material needs to be the same thickness as your panel or close to 18-20 guage. Do some practice welds on a scrap piece to get your welder settings figured out. You will probably be on the lower settings for heat and wire speed. When welding on a body panels you NEVER make long welds. Make small tack welds about 1/4 to 3/8 long. Allowing time to cool. I use a wet rag and/or air hose to speed cooling. Tack weld the panel in a criss cross pattern like torquing a head, If you dont you will have shrinkage that will pull the patch gap all out of shape. When finished you will probably have some shrinkage that will require some hammer & dolly work to flatten out. Welding and body work are a skill that takes time & patience. You can always stop by your local body shop & bug an employee. If you find a Mopar fan you will probably get some good tips. Hope that helps Good luck  

You can weld it from the back side of the panel. That may cut down on your grinding.

Theres no way your going to be able to lay a bead on sheat metal and not need to grind it down though  

Thanks for the tips GTX. I think the mistake I've been making is working to hard to leave no gap between the 2 pieces of metal. I have also been trying to just spot weld it and not run a bead. I spot then move to another area and spot again. Once I have the entire piece tacked all around at several inches apart, I'll go to the middle of each space and continue until the entire area is filled in. Warpage hasn't been an issue, just the penetration, since when I grind the weld off there isn't much left holding the parts together. I did weld my fender patch on the inside of the fender, but I don't want to leave a weld.... looking foe  clean job on both sides. I'll practice with a gap and see if I get better at it. Thanks again.