How Do You Repair a Warped Panel??

I am still working on my trunk lid. I got a 6" strip welded in up on top and was very careful to skip around, cool the welds, etc. to avoid warpage. I was successful doing that...

So I go to grind the welds down (used a MIG), and used an 80 grit flap wheel on my 4.5" grinder. I jumped around grinding down the welds, cooled where I was grinding w/ a wet rag and really didn't notice any appreciable amount of heat build-up. However, the patch panel is no where near flat now. I can probably flattened it out w/ body filler, but is there another way to take out the waves and dips ?? I've heard about shrinking discs, but don't own one and don't know where to buy one... Not sure the correct method to straighten it back out.....

Also, what is the correct way to grind out welds to avoid this in the first place (assuming I stick w/ the MIG)??? I still have some more to finish up.

Any suggestions from you experts ??

OK, let's BTT this topic, I'm in the same boat with a lot of MIG welds to deal with.

So how hot were you letting that patch get? My guess is, the smaller the patch the less heat it will handle before warping.

I didn't let any of my metal get hotter than luke warm before I let it cool (on its own - not water, etc.) I planned to do the grinding the same way. Basically weld (or grind) a few seconds every 4" or so down the whole weld, then wait 5-10 minutes and do it again. During cool-down I work on another part of the project - I think MIG is giving me ADD!

May be wrong or overkill, but it seems to be working so far.

A shrinking disc will help smooth it out. Probably wont eliminate filler but will greatly reduce it.

By marking out your welds at two inches and welding alternate welds, top to bottom-side to side - cornor to cornor - left then right, will help in keeping the warpage down to a minimal.During the grinding part of it, try and keep the grinding wheel or disc as flat as possible so as not to dig at the weld with the edge of the wheel or disc and don't try to take the weld down to the panel all at one time, do it slowly.

need help

find a 80 year old bodyman and get him to teach you the art of metal shrinking witha torch
may be hard to find one that can still breath

thats what i did. hanging out with old rodders is one of the best things ive ever done.

grinding

you need to use a 4 inch grinder with a welder grinding dics on it grind it down so far the use a 24 grit disc to finish it off move around alot to prevent worping

mcc7 said:

you need to use a 4 inch grinder with a welder grinding dics on it grind it down so far the use a 24 grit disc to finish it off move around alot to prevent worping

Click to expand...

Man, I am learning this the hard way. I got bad advise from some other cats. The grinding disks work WAY better than the flap wheels I was using - quicker work of the weld and less heat.. Live and Learn....

you can't work careful enough with sheet metal.

you're tacking, walking away, plug weld, walk away...

always skip around, never cool with a wet rag unless you're trying to shrink an oil can area. rapid cooling makes sheet metal brittle and hard to work.

this is a job to do while you're doing another job... bounce back and forth, and keep an eye out for the smoke genie!!!!

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in my bodywork trade I use a cut off wheel, with a thick 1/4'in wheel to knock down 80% of the weld nugget..

then come back with a whizzer wheel with 35 and smooth them out.. then filler

any of your warping is coming from the welding process... if you're warping the sheetmetal with a grinder, you're riding the grinder across the panel!

while grinding, if you can't hold your hand to it, it's too hot!! slow down, speedy!

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your current situation sounds like you need to make a relief cut.. if a panel is too warped stressed and fubar, you may need to slice it in the middle of the sheetmetal bind, weld it up, then "cave it and pave it"

Shizzle, yeah I think I got hot w/ the grinder. I actually ended up cutting out part of the area and redoing it. I was going along great until I had that snafu and got the fubar result !!

I have laid off the lid for a while - been doing some firewall, painting, motor and rear end work.....

I will get back to that eventually when I get the motor fired off.

I would do it with the 1/4 " cut off wheel. Then going back with finer grits such as 50-80. I wouldnt use 24 or 36 as it puts some real deep marks in the metal and you will never get them out. Especially if you are metal finishing the panel.

Take your time and dont be in a rush and your metal work will show from this.

A friend and myself chopped the top on my 37 sedan. What an incredible amount of work, but it was worth every minute. He was an experienced welder unlike me. He would weld a couple of spots and then walk away. It drove me crazy becuase I try and do everything quick. I'm glad he did it that way and we didn't have any warped panels. Just take your time and listen to these guys as there is a wealth of information on this site......CR