The Stovebolt Site Forums The Shop Area Paint and Body Shop Cab corners - butt weld or lap weld?

Hello!

I just finished welding in the inner cab corner on the pass side of my '59 Apache. Next is the outer corner, but here's the issue.

When I bought the truck, I didn't realize that it had been hit pretty hard in that cab corner. Someone fixed it by banging it out, re-welding everything, and coating it with about 1/8" of bondo on the door jamb (behind the door, about 1/2 way down). Now that have the old outer corner off, the bondo is coming off in pieces, so the contours of the sheet metal that I'd be welding the new corner to don't match the new corner very well. The sheet metal has been pushed in a bit, between 1/8 and 1/4", and the previous owner's straightening efforts have pretty much made the panel impossible to straighten any more.

I was going to butt-weld the new panel in using clamps, but now it seems as if it might make sense to use flange pliers to make a 1/2" flange on the body, then fasten the new cab corner to the flange on the body using sheet metal screws. Doing so seems like it will pull the body panel the small distance it needs to move to get everthing to line up. Of course, once everything is where it should be, I'd weld the new corner in place, remove the screws, and weld up the holes.

My understanding is that a butt weld is the best type of joint for a body panel, but it seems as if a lap joint might make sense in this case.

Thoughts?

Thanks...

Chris

Chris, I dealt with the same issue in restoring my '36 Chevy pickup. If you're doing real metal work without bondo, butt welding is requiired. The weld is then ground smooth to yield a single piece of sheet metal. Lap welding is for bondo plasters. Bondo is quick and dirty and definitely works and it's what the "pros" use to enhance the bottom line. But absolutely no skill is required and I don't see how there is any workmanship pride in using that stuff. It's like smearing peanut butter on a slice of bread, then waiting a few minutes and hitting it with a cheese grater and calling that "body work".

I have never had much luck with crimping curved metal. I prefer butt welding curves. I weld a small spot, then bump the metal to where they meet and then weld another small spot. The clamps don't work as good as it appears in catalogs. I have sheet metal screwed sheet metal to something like 1/8" strap bent to the correct curvature with pretty good results. But the whole trick is to weld small enough spots to prevent warpage. I would try to repair what you have before you do anything. You might read this book.
http://www.amazon.com/Key-To-Metal-Bumping-Book/dp/B002S4Y7RS
It is almost 60 years old, but it is still very much on point. Something that is not mentioned in the book is a shrinking disc. I have had good results using one. Repairing previous repairs usually involves shrinking stretched metal.

Yar and Cren -

Thanks for the replies. I have the metal bumping book in hand. It's been helpful, but the situation I'm dealing with, multiple compound curves, is a tough one for a beginner like myself. I have a set of harbor freight dollies and hammers, and I was actually able to get things fairly close using them. Now I'm at the point where I'm within 1/4" or so, and that last bit is proving quite a challenge.

Because the area was already hit, straightened, ground, welded, and fixed with bondo, I've resigned myself to the fact that I will have to use some bondo to make it perfect. I'm trying to keep it to a minimum, though.

Cren, if I can't gradually work the panel into place as I weld the panel, I'm going to try to try your suggestion, back the gap with a piece of sheet metal and pull everthing into place with sheet metal screws, butt weld the joint, then remove the screws and the backing sheet metal.

Thanks again...

Chris

Chris,I'm another advocate of butt welds.

I attempted this repair on mine and as a complete novice I am more than happy with the outcome.
I've always considered lap joints as moisture traps.
I also have no qualms about using a small amount of bondo,purely to tidy up the weld seams,rather than carving the panel to shape.

We would all love to have the ability to metal finish,but I personally do not have the time or patience to attempt this.

I had a VW Bug a few years back and the PO repaired the rear 1/4 panels with lap joints, the repairs didn't last well.

Jockbolter 50, from my experience doing the tricky procedures in metal working benefits greatly from beginning by having proper technique demonstrated. Back in the early 1970s when I was restoring my '36 pickup I took an evening adult education class in body repair. The instructor was the owner of a body shop.

Even then he acknowledged that body repair without bondo was a "lost art" in the commercial shops. He was, however, a master of that lost art and demonstrated for the tiny handfull of those of us who were interested ultra-light gauge metal welding, hammering the weld, bumping metal into rough shape, hammer/dolly finish metal shaping, finding high/low spots with a vixen file, pick hammer use for raising of low spots, minor shrinking with a "slapping file", major shrinking with an oxy-acetylene torch/hammer/dolly/wet shop rag.

I was awed by what could be accomplished with the most simple and crude of "old school" tools. Forty years later I still like looking at my restored '36 pickup and going down memory lane about all the skills that restoration project taught me.

Recently an old friend who is building a auto cross race car with his son asked me to shrink a damaged panel on their race car. To my total amazement I could still do it, kind of like never forgetting how to ride a bicycle. So, once learned, those skills are with us until we're sitting in the rocking chair drooling.

I will admit that the world has changed since then and the emphasis now is on speed of finishing and low price, not quality. That is why China's economy is thriving.

Not sure about your year truck but my suggestion would be to fit the repair piece so that you have the gap and contour matching the door. Then work the rest of the cab/jamb to line up with that.

If I read correctly the jamb gap was previously "corrected" with plastic filler. This something you must avoid, the edges of panels should always be metal so keep that in mind.

HERE'S A PICTURE of the kind of "clamps" I used to keep the surfaces flush. DETAIL SHOT of the clamps.

Good luck!

Czechman, I like your clamps. Looks like they are aluminum. I forgot to mention with my straps, I put shim brass stock in to keep the weld from sticking to it. What I criticize is the clamps that places like Eastwood sells. They wouldn't hold the piece in place, much less keep it from crawling. And you have to bump it a little between welds and the Eastwood clamps would probably fall off. The big challenge is to have the two pieces fitting correctly before you ever turn on the welder. I was guilty of that 50 years ago when I still used gas and coat hanger wire. Don't even think of welding until everything is in place.

I laid down a lot of tacks between my clamps then removed them and ran my bead. I used one of those magnetic copper backing thingies when I welded up the holes where the screws are.

They worked very well, had a lot of clamping power and were dirt cheap.