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Has anyone had success welding patch panels into their bed panels? I’ve tried 3 times now but keep having to cut it back out because it warps the whole panel so bad. It’s now about a 14” x 14” patch (keeps getting bigger every time I have to cut it back out. It’s right in the middle of the panel. I’ve tried all the tips and tricks. Is that panel just to big and flat to be welded without warpage or is it actually possible?

Yes. I successfully replaced the sides and the bottom part of the front panel on my bed. I overlapped the panels and plug welded them. You can see the overlap in the picture.

How do you blend it when you overlap the joint like that? Just grind and filler? Here’s what I’m dealing with. Not sure how I could do a lap joint here.

Are you using the multiple dot weld technique advised by MPandC here? Weld a series of well spaced dots and planish them to remove the shrinkage, then repeat till the whole butt seam is welded.
I see that you're using the weld clamps that force you to have a space between the edges. You'd be better off without them, clamping the pieces together with minimal to no gap.

Another technique that's been advocated by some is lap your patch over the original metal and then use a cutoff tool at a 45 degree angle for a short distance, weld that section and then cut some more. I haven't tried that but I have welded some pretty lengthy patches in my bed sides and was able to deal with what minor warpage occurred by selective stretching and shrinking.

My first attempt was the bottom section of the front panel. Link
Here's another one that was pretty involved, with two intersecting patches. Link

I definitely did the stitch and move method. I go very slow. If there is no gap how can you get decent penetration? I do have to turn the voltage way up to get the weld to go all the way through. I’ve seen that method (lap, cut,weld) but I’m not sure if that would help with warpage. I thought of welding my angle strip on first to keep the panel straight. Hmmm

I didn't try to put in a patch like the one in the picture. I don't have the skills to make the patch disappear.

I removed the stake pockets by drilling out the spot welds. I cut the top rail off a couple of inches from the top. A new piece of sheet metal was cut to size. The top and stake pockets were plug welded onto the new side.

Welding patches in bedsides and doors will test ones patience. If you are going slow, you need to slow down. Slow isn't slow enough. You should be able to touch the weld without burning yourself before you start another series of dots between the ones welded prior. Plannishing the hot dots with a hammer and dolly will help prevent warp and transfer the heat from the dot to the hammer and dolly.
As far as how high to set the amperage of your welder, its higher than what seems rational. You want to buzz a hot dot almost instantly. A low amp dot will take longer to get full penetration, thus increasing the amount of heat spreading into outlying area of the panel causing warp.

What Carl52 said.
Use some scraps to set your amperage. They should be unsupported at the weld point like the patch would be. Crank up the amps till you burn thru, then back off just enough to get full penetration. Practice makes perfect.

Another trick is to avoid sharp corners on your patches. As large a radius at the corners will help reduce the warping.

It will take a looooong time to get that size of a patch done. If it takes days, that's what you need to do.

I did as you say with going so slow, each weld was cool to the touch. It took me 3 days to try this last patch and I’m going through 80 cf bottles of gas like crazy. There is a point where the patch starts to bow up and is no longer flat. Maybe it’s the plannishing that I need to work on. I appreciate all the advice. It sounds like you guys do think it’s possible to weld such a flat panel successfully. I’m debating if I want to try one more time or if I should just by a new panel. I hear what you are saying with cranking up the heat. Especially if there is no gap it’s really challenging to get the weld to go all the way through.

Hi 49shep,
I recently had a stainless steel shower trim part custom made for a bathroom renovation. Fortunately I have a high school friend who is a highly skilled and trained welder - straight up welding magician intuitively skilled on all welding technologies and watching him work out and decide what methods to use while making my part was something you could make a television show out of.

Anyway, he described that if you do or don’t want a gap between the two parts depends how you feel you want to weld it
Thin as this job sounds seems similar to the 0.0625 stainless we were butt welding
He decided no gap - tig would yield a good polishable weld and he was correct
However some post folding and bending joints left about a 1/32 to 1/16 gap which needed a filler mig wire placed in the crack to resume tig without filler rod

He backed every spot with a lot of aluminum scraps to sink heat
And jumped from opposite sides of the work to allow heat to dissipate
Also some of the aluminum blocks got a bit too warm so we would put those aside and get fresh off the floor cold ones

Once A tack weld is done it might be a bit proud or bumpy that tiny extra material is holding stress, just flattening the first tack welds restored flatness and makes a difference
Once the part is tacked up and the tacks are dressed to return flatness at cold then you proceed to more tacks between the first set
Repeat

All extra metal from the weld is pulling (shrink) so removing the excess to flat helps a lot
After it’s flat gently tapping on the welds at the right place will return the panels to completely flat
Don’t weld too much on a warped panel unless you know for sure the two edges are uniformly warped at that instant and the natural flatness would keep those two edges uniform in the end - if the edges are offset from their true position due to intermediate work the welded position will lock in the warpness.

49shep, Too bad you're on the West coast. If you were in Maryland, Robert (MPandC) could fix you right up. My mom lives up the coast just a bit from you, and I get by there every year or so, and could help out. But you probably don't want to wait that long.

You said you were using many bottles of gas. Are you using Oxy-Acetylene or MIG for your welding?
O/A takes a lot more skill (at least in my experience) to get a good weld.

Each weld spot shrinks a bit as it cools, and pulls the panels together. Robert has demonstrated how to get the right amount of planishing by welding a sample with two dots, and observing how much the gap shrinks, then planishing till it's back to the original gap. He may have a link to that in the thread I linked. It's well worth reading every word of it and looking at all the links he posts.

I’m using MIG. I appreciate all the responses. I think you guys have given me some things to work on. 1) I will tighten up the gap between panels 2) Try use some kind of backer. 3) I’m already going so slow but I think I need to assess panel warpage with a straight edge much more frequently 4). Remove excess material more frequently, not waiting until the end to do all the grinding. I need to work on planishing technique I think, it’s kind of the worse part of the job. Ill give it another shot this week and see how it goes. Thank you

One of our own MPandC, did a guest appearance on Manic Mechanic on YouTube, and is one of the best tutorials on the dot weld panel replacement procedures I have ever seen. Definitely worth watching! Here is a [LINK].

That’s very helpful. I had read the tutorial on here but seeing the video is really great. I couldn’t find anything on YouTube that was detailed enough. The planishing is much gentler that I’ve been doing. I’ve just been pounding away and giving myself tennis elbow. My neighbors really were starting to hate me. Thank you!

Ok. I feel like I’m doing everything right here. Going so slow. Planishing every dot then cutting down dot with cutting wheel, checking with a straight edge as I’m going. Seems much better but I think Im starting to get a slight crown in my patch. I can tell because when I lay the angle strip on as a guide if I have to push it down slightly. It’s slight and not a big problem yet but Im not sure how to fix it.

Im not an expert

The bulge is because as the welds shrink they also pull parallel to your seem
This means extra metal in the middle as the edges get shorter
It might go away when you expand your welded seems ever so gently

Im not sure if this bulge can be set aside until you are done all welds or if you should do an intermediate remedy.

Personally I would attempt at slowly finishing the weld as long as I only see a bulge and not full on waves because there is just so much extra metal it can’t fit in one curve
Then I would tackle the bulge
suggest you watch a few videos on how to shrink sheet metal
You will need a torch and a wet rag
Figuring out where to try to shrink it just right is the skill part
I usually am not aiming for perfection

So let’s collect more forum feedback don’t run off and do what I say
That might make it worse
-s

2ManyTrucks is correct in that the metal shrinks lengthwise along the weld, but you should be able to minimize that as you planish the weld dots. You may have to do some shrinking, but as he said, figuring out where and how much to shrink is a bit difficult. Oil-canning is indicative of a panel that's been stretched (or shrunk along the edges - the effect is the same).

Your latest attempt looks pretty good so far. I would complete the welding of the patch and deal with minor bulging after you're done.

Ok. Cool. Thank you. Working on it little by little after work. Thanks for walking me through this. I’ve slowed way way down. You really need a chair and something else to do while doing this.

For a backer, I have taken a piece of copper pipe and made various backers. One is a 3” long piece placed over a piece of steel flat bar and squished flat. Another is a 3” piece split open and then hammered around an old dolly I had laying around. And my third is another piece slid over a piece of steel cold roll. These have worked extremely well for me and are cheap. If you have a chunk of copper tubing kicking around that is...

An idea of speed... it took for nearly 4 days (IIRC) to TIG my upper tubes on my 1/2 ton bedsides. Go slowly!

If you're doing a flange/overlap joint, you can use a common MAAP torch, acid flux and Harris Stay-Brite silver bearing solder and not worry about any warpage, etc. That solder melts at around 430 to 450F and then finishing the work when you're done is easy and quick. Sort of like working lead. Plus that solder is about as strong as a brazed joint. In fact on something like this, you can turn days of work into an hour or so. Good luck.

I can't argue with that, but if you use acid flux, you better use something to neutralize the acid afterward.
Evan (coilover) would probably advocate the use of panelbond.

I think I was successful with my butt welding. Took me a long time but seems to have turned out decent. I give myself a B- . My patch was crowning for sure. I used a stud welder (dent puller) to heat small spots, hammered then cooled and I was pretty successful at flattening it out. I think the only thing that I had some trouble with was getting the welds to go 100% through to the other side. You can see there is a slight line on the backside in about 25% of my welds. I could touch those up but I really don’t want to add anymore heat to this panel. I’m hoping epoxy primer and filler will do the trick and I won’t see any cracking down the road. For those attempting this my main advice is to watch that YouTube video, get yourself a chair and beverage of choice, do not skip plannishing each and every dot, grind down your welds with a cutting wheel as you go and go super slow, checking your work as you go. Thanks all for the help.

I’m so happy it turned out well and you managed to do it yourself
The next one will be even better!
Now put “body repair” on your resume
-s

X2 - Good job. Getting the panel flat is the hardest job, and it looks like you got that down.

I'll admit to having a few less than full penetration welds in my work also, but this isn't a high stress panel, and I don't think you'll have issues with cracking. If you have a sandblast gun (I got one from Grizzly Industrial that has rubber nozzles and a collector bag on it), I'd recommend you blast those pits before applying your primer to keep from dealing with any rust in the future.

Also recommend after blasting your pits to use a self etching primer on raw steel before applying any filler to make it smooth
Body fillers don’t bond well to raw metal they require binding onto the primer
If you fill on metal the boundary will rust and the filler will delaminate from the rusted steel in a few years down the road
Like every used car I’ve had the pleasure of owning
-s

A Direct-to-metal epoxy would work as well.
The body fillers I've been using (All Metal, and Contour from Eastwood for finishing) both say they work best on bare metal. If you shoot primer shortly after filling, you shouldn't have issues with rust.

I’ve been using SPI epoxy. They suggest epoxy first then filler. As much as I would like to sandblast, I live on a suburban Southern California cul de sac and the mess is just not appreciated my neighbors. Plannishing 10,000 welds at 9pm didn’t make me any new friends.

yeah modern fillers are probably much better on metal than the fiberglass bondo junk i'm used to seeing from decades past
i haven't used any of these epoxy fillers yet, i'm usually content when the hole is patched with metal and i can't see the ground

being mindful of your neighbors is a very noble thing to do, i applaud your level of self awareness
-s

Here's the sandblast gun I have. It would be ideal for blasting your joints. Unfortunately Grizzly no longer sells them. It has nozzles that contain the grit, making for very little mess.
I hear you about the 10,000 weld dots needing planishing.

Nice work! Glad it turned out as good as it did!

I would weld those little holes shut. You already figured out how to go slow.