Welding Tips and Tricks

Hi guys. Newbie here, very experienced solderer now turning my hand to welding at 73. I would appreciate a little guidance on the setup of a job which would be chicken feed to you.

As I said, I'm doing a simple enough job patching in a long low section into a car sill. The sill has rotted out in its lowest few inches towards its rear through being left to stand for a long time with water sitting in it, (drain holes blocked with factory sealant, that's Peugeot for you.) It goes from about one third of the way back to about two inches in front of the wheel arch edge. The rear will have the same issue as the front which I am describing here.

I have the section cut out and prepared and I know basically what I have to do but I have some across something not intuitive to me. I have a joggler and thanks to that I have a good straight recessed long top edge to the hole. The bottom is clear to the inner sill and back to clean metal. The front end of the patch is only about 2/3 up the sill. This means that the front vertical edge, about 6-8 inches round the bend from the upright surface to the inner sill under the car, follows a very curved line from top to bottom. I can't see that I can use the joggler to prepare it as it seems to me it would straighten the curve out to a series of short straight sections.

So to my question, is it usual to simply butt the vertical edges of a curve like this and weld very basic edge to edge? Or is there some trick I am not aware of which would make it a better job?

Butt welding for body panel repairs is very common.

A couple of things to know:
Many people say, “skip around as you weld to avoid distortion”. Doesn’t really stop it because the heat accumulates across the part so distortion is going to happen. Instead, plan for it and weld with that in mind.

If you’re using MIG, weld vertical seams downhill; this helps control the heat. Don’t place tacks “every few inches” in the seams. This makes the distortion worse and often creates bad ripples.

Intentionally, leave a small gap. Use 0.024 MIG wire, not 0.035 when welding panels. Cut a few strands off and fit it into the seams. Make the gap ever so slightly larger at the end of the seam, and weld toward the larger gap. As you weld, the panel will expand and the gap will close. If the seam is butted tight, as you weld the expansion causes the panels to distort because the expansion has no room to occur.

You probably need a dolly and hammer also to coax the distortion out as you go. Do a section, dolly it, do another, dolly that, etc. Don’t wait until the end to do your dolly work because once welded in fully, the panel can’t move.

I am a huge fan of SilBr wire for body repair. You must use 100% Argon gas, but the heat affect and resulting weld are much easier to file/sand/grind.

Hope that helps and answers the question you asked?

Thank you so much for all that great info CJ. That is exactly what I needed to hear. I'm on the right track with how I was going to approach the job, but to get those tips as to how to improve the finish is a bonus. That's sorted my immediate problem I think, and maybe left things open for discussion with others who may have other info to pass on. It all helps people like me to move forwards and improve.