body work problems

spade33 · Dec 28, 2007

hey all its been a while since i have been on here or at least posted (really busy between loosing the gf and christmas and all haha ) anyways i got a body work question. so ive got my car striped down and im working on the rear tailight panel and it had been hit pretty hard at one time (found almost a half inch of bondo in it ) anyways my question is... some of the metal seems to have been stretched so its popping in and out when i push on it(i hope that makes sence) but i was woundering if anybody had any advice on how to shrink the metal back so i can get it flat? i would rather not have to replace it with some metal of my own but if i get stuck to that i guess i can give it a shot. thanks again guys :SNSign:

zookeeper · Dec 28, 2007

This is a VERY oversimplified descrition of my favorite method, but hopefully you can practice on a scrap panel first and get the hang of it. If you have a panel that's stretched to the point of popping in and out, you need to shrink it. What I do is put a small tip on a torch and heat a dime sized spot at the point you want to shrink. Get it red, then apply a wet rag to cool it. If you have a crease at the high point, you can do this with a series of shrinks in a line. After shrinking two or three spots, recheck your progress. If you are trying to correct a large dent, make your spots in a circle near the center. Always cool each spot before moving on to the next and keep checking your progress as you go. If you don't have a torch, you may want to buy a stud gun used for welding studs on dents and creases to pull them out. Stud guns have a "shrink" setting on them where it just heats the metal but doesn't weld a stud on. Older cars like vintage Mustangs have sheetmetal thick enough to shrink, but trying to do this method to your new car is (in my opinion) a waste of time. The metal is too thin and severe warpage is about all I ever get done. Good luck!

danny clemens · Dec 28, 2007

There is also a disc designed to shrink metal. It works basically the same way a torch does but is supposed to keep the heat only in high areas. I need to order me one because everyone who has used them swear by them. I'm not knocking the torch method because it's been around a long time but the people who use the shrinking disc say that it is easier to work with.

Go to www.hotrodders.com click on bullitin board and go to the body forum. Do a search on shrinking disc. I think there is even a video somewhere on there demonstrating one.

zookeeper · Dec 28, 2007

He's right. I've never used one, but everything I've ever read says the disc is quite a tool. I think Sunchaser Tools either makes them or sells them.

danny clemens · Dec 28, 2007

There's a discussion going on over at hotrodders right now. http://www.hotrodders.com/forum/body-work-shrinking-disc-130440.html

xoxbxfx · Dec 28, 2007

spade33 · Dec 29, 2007

hey guys thanks alot. i thought i had heard of the tourch method but i still had no way of knowing were to start. at least now i have something. and the disc sounds intersting. may be worth a shot.. i have another option which i can not decide whether its worth it or not. my uncle has a 66 coupe like mine and he said if i wanted i could cut the back panel out of his..(i only need about 20 inches of the center section) and weld it into mine. i am a decent welder and my neighbors are increadible at it if i needed help. my panel is all jacked up and the gas filler neck hole,.. haha is alll mangled up so i have been tossing that idea around in my head what do you think?

xoxbxfx · Dec 29, 2007

try the torch method if you have one..its alwys worth a shot. A fill taillight panel isnt much though, I wouldnt cut up another car just to patch it...just buy one.

spade33 · Dec 29, 2007

that is true is one life worth more than another? hahaha

xoxbxfx · Dec 29, 2007

spade33 said:
that is true is one life worth more than another? hahaha

is it ok to kill a homeless man to make him an organ donor to save another mans life?

http://dallasmustang.com/page/products.php?category=&group=&family=&product=3712
$60

Hack · Dec 29, 2007

There can be a problem when you quench with water - it will harden the metal and can make it prone to cracking. However, it does speed things up and a lot of people do it.

Another way with heat is exactly the same as above, get a very small red spot and then quickly use a hammer and dolly to shrink it (just a couple strikes). Then wait for the metal to air cool rather than quenching.

danny clemens · Dec 29, 2007

I believe that I would change the whole tail light panel rather than patch a 20" piece in. They're not that hard to do. If you weld in a 20" patch you're going to have to deal with the weld area getting out of shape. Then again an experienced sheet metal welder could probably weld it in with minimal distortion.

truck90278 · Dec 29, 2007

Hack said:
There can be a problem when you quench with water - it will harden the metal and can make it prone to cracking. However, it does speed things up and a lot of people do it.

Another way with heat is exactly the same as above, get a very small red spot and then quickly use a hammer and dolly to shrink it (just a couple strikes). Then wait for the metal to air cool rather than quenching.

Caution here, if you place the dolly directly under the heated spot and hammer directly on the dolly you will stretch the metal more. You have to use the "off-dolly " method. Place the dolly on the low spot and hammer next to the dolly on the hot spot, quenching with water will further reduce the the stretched area. The poping in and out is also refered to as "oil-canning"

With the amount of damage, you probably would be better off simply replacing the rear panel. It would be easier and less time

Hack · Dec 30, 2007

truck90278 said:
Caution here, if you place the dolly directly under the heated spot and hammer directly on the dolly you will stretch the metal more. You have to use the "off-dolly " method. Place the dolly on the low spot and hammer next to the dolly on the hot spot, quenching with water will further reduce the the stretched area. The poping in and out is also refered to as "oil-canning"

With the amount of damage, you probably would be better off simply replacing the rear panel. It would be easier and less time

You are right that hammering directly on a dolly stretches metal, but when the metal is hot it expands. When you have a dime sized area of red hot metal, that small area will not be flat. That's why you can put the dolly directly under the hot spot and strike the spot only once or twice. You are not really on the dolly because the small hot area is raised so much. This is what shrinks the metal, because the red hot area is high and it's also relatively soft, so it will shrink more easily.

This is also why I said to only hit it once or twice, because once it becomes flat then you are hitting on the dolly and you can stretch it back out.

I agree that replacing the panel is a better way to go. Shrinking is not easy, even for experts.

chromedog · Dec 30, 2007

ive found the best was to shrink a dent is with a fair amount of heat, and a shrinking dolly. it has a serrated surface, mush like a meat tenderizer, and it gathers the backside of the metal, and makes it much easier to draw the metal back in, along with cutting down on the oilcan effect...

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