Weldding Question

[grey beard]

I'm about to replace a floor pan on my B1B pickup. I have a nice donor pan to use for replacement, so the repair panel should be a good fit if I trim carefully. My quesion is this: Is butt welding of dsheet metal panels superior to overlapping the patch over the parent metal? Seems to me that I could make an oversize patch, drill holes in the edges and resette weld through the holes to get the job done with less heat and warpage, but I've never done this. Might make clamping and alignment easier too. Which method is stronger?

Do any of you have experience in this area you might be willing to share? I'll be using a mig/gas machine. Could also oxycetylent weld or braze, but my understanding is that these options are not as strong. Suggestions or ideas?

Thanks,

[Rich Gengo]

Overlapping a panel is quick and easy and will work fine if your not concerned about looks. If you cut it neatly and just overlap it a little and put some seam sealer on the edge it wont be so bad. The problem is where you overlap it is where the new rust will start if you don't seal it. What I have done on panels is I'll put my good piece over the bad one and use Clecos (fancy removalable rivit like thing) to hold panel in place. Then you get a cut off wheel and cut through both pieces.Go a few inches at a time. Make sure you use a thin wheel (1/16). Peel back the metal and you can tack(Mig) the old panel to the new panel. Use a little pocket screwdriver to bring the two pieces up to the same level before you tack it. Continue all the way around just cutting and tacking about an inch apart. Now the excess top panel will come off and the bottom piece comes off leaving you with a new panel blended in. Just keep tacking all over till your done. I cool each tack with a wet rag to prevent warping. Then grind the tacks smooth top and bottom if you want and nobody can tell it was done and no place to trap moisture. Not hard at all but does take a long time depending on the size.

[Don G 1947]

I don't think strength is going to be an issue no matter what technique you use. It is only a floor pan. If it does fail it will be because of poor welds and not because of gas welding vs. MIG. The problem with welding thin sheet metal is warping and burn through. To avoid/minimize these problems use only .023 or .025 wire in your MIG. The thicker the wire the more heat---the more heat the more warpage and burn through. As Rick has suggested, tack a short section about 1/2 inch and then move to a cool area and do another 1/2 inch. Keep doing that until the entire panel is welded. If you don't let it cool down you will get warping. Welding shrinks metal so if you come to one of your 1/2 welds and it is buckled, use a hammer and dolly to smooth it out. If you just weld next to it the buckling will be compounded. Unless you are very good with gas welding or have a special sheetmetal torch (I think Eastwood carries them) you will be generating too much heat and have lots of buckling.

Good luck and let's see some pictures when you are done.

Don

[bach4660]

make sure all of the old firewall pad is removed, I forgot a piece behind the heater and got a very unwanted fire ( the heat melted the rubber in the cowl vent)

[Don G 1947]

One of the things I should have mentioned in my earlier post was that you can also reduce warping and burn through by backing up the area you are working on with copper or aluminum. They are great heat sinks and weld won't stick to them. If you have a hole wou need to fill you can bridge over the hole if you back it with one of these metals.

Don

[Young Ed]

I think the guy helping dad and I weld had a brass block like that. What we never figured out was where to get something like that?

[Guest Dave Claussen]

You might try looking at a metal recycling center if you have one near you. They buy scrap copper/aluminum and would probably be willing to sell you a couple pieces for the scrap price or a little more. I have also seen flat pieces of copper and aluminum stock at Ace Hardware, TSC, Sears Hardware, and occasionally at hobby shops.

[anthonyb]

If all else fails, go to anyplace that sells copper pipe. A few seconds with a hammer and you can have a backing plate with a handle.