Where to draw the line on cut and replace?

I would hold a heavy dolly on the back side of the weld and hammer it from the outside in to stretch out the weld seam. You may want to lightly hit it with a grinder first to make it more uniform and to get rid of any high spots.. Leave some of the weld though because you want to leave some metal to push back into the panel to help stretch it out.. I've actually used a ball pein hammer for this in the past when you need a lot of stretch, but grind the outter edges of the hammer head to make sure it's smooth. I've since switched to tig welding and it has helped me out quite a bit.
 
and stop going back and forth between stretching and shrinking. you need a LOT of stretching before you have to worry about shrinking anything,, it's pulling in pretty hard so it's going to take a bit of hammer/dolly work.
 
Thanks Chad, I'll try stretching again. Worse case scenario is that I cut it off and try again. Only next time, I think I'll try TIG weld. Meanwhile, I'll work on the other quarter panel.
 
Chad gave you some good advice, all your attention should be on the weld itself. Grind it down but not all the way and do the back side too. Be sure to use firm pressure on that dolly to be sure you are stretching and not beating the panel inward.

And yes, next time start at one end with the tack welds and planish them as you go to keep things in alignment. Once you get the hang of it, you will not want to use a mig.
 
Yes, I appreciate the good advice! Just to clarify a few things... This was gas welded with tight butt-joint. Hammer and dolly with ball pein and body hammers on the HAZ for at least 8 hours to stretch the weld. Improper welding technique: I welded from both ends to the center to try to "chase" the old stretched metal to the center of the panel where I thought it would be easier to shrink it out. I'm positive this is where I went wrong.
 
I guess what I'm trying to say, is that I AM following everyone's advice, but it isn't working. So, either my technique is wrong, I didn't do it enough, or I hammered it too much and didn't realize it, or that's not the real problem. In an act of desperation, I hit the center of it with the torch (the big burn spot), then hammered that area some more, then gave up... Before hitting it with the torch the final time, I had the weld planished smooth but the panel was still bowed in about 1/2" inch. The more I hammered the weld, the deeper it sunk! Before I started, the old stretched metal was bowed inward, and that is approximately where it is now. The new piece did not pull the old metal to the proper place. Instead, the old metal pulled the new metal to the wrong place. Does that make sense?
 
MX442;30668 said:
Before I started, the old stretched metal was bowed inward, and that is approximately where it is now.
Click to expand...

That's a major part of the problem-these parts need to fit really well without distortion before you weld. Gas welding always puts more heat into the panel and causes more shrinkage-I only gas weld if I have good access to the backside because there's going to be a lot of movement. Post up some pics as it is now and maybe you'll get some recomendations on a plan of attack to correct the problem. Sometimes you need to recut a portion of the seam to get it corrected.
 
Sometimes you need to recut a portion of the seam to get it corrected.
Click to expand...
Thanks Bob, that's the plan for now. Correct the bad weld. LESSON learned! I'm working on the non-welded quarter, trying to figure out where to shrink it. I'll get the whole right side of the car straight, then jump back over the the welded QP. Plus other irons in the fire, I won't have this thing painted before winter. Maybe next year...
 
After a long break, I got back to working on the Olds over the last month, and finally got-r-dun. Following Bob's advice, I ended up cutting it off at the weld. I worked it flat again on the work bench and smoothed out the waves in the old metal.


Having a hard time welding in the fender lip, I also cut out a portion of the quarter panel to weld the lip to before welding that piece back in. There is no room near the fender lip to dolly on the back side. Welding on the workbench was a lot easier.


Then, I tack welded it back in. After every other tack weld, I ground it and hammered back to shape before continuing. Once it was tacked, I started at the fender lip and welded toward the rear. After every inch or so, I ground down the weld and hammered back to shape. By correcting the shrinkage as I welded, it didn't get away from me.

Finally, DONE! (just a few ripples to iron out)

 
looks good! takes a lot of time but the results are worth it!
 
You must log in or register to reply here.
Back
Top