Has anybody tried heat shrinking?

[Joe Flanagan]

I saw a video on Youtube that demonstrated the technique. Seems really easy to do. I have a section on the roof of my Plymouth that I think is oil canned and I'd like to try to shrink the sheet metal. It looks like a dent but when you push it up from the underside, it's really flabby and has no stiffness at all. You can push it up as easily as you can push it down. So I assume this is oil canning. The video showed a guy heating the metal with a torch and cooling it with a wet rag. I saw other demonstrations with a heat shrinking disc, but the torch and rag technique seems so easy, plus I have both a torch and a rag. Can anybody offer any advice?

[55 Fargo]

You could try it Joe, on this section using a wet sponge, you work areas the size of a dime.

I am not experienced at all in this, but really think it's a learned talent, wish I could offer more advice......Fred PS what brand of respirator mask are you using, may buy what you have, if available in Canada, most brands are sold here, 3M North, MSA. I have the MSA Advantage 200, with P100 filters

[Joe Flanagan]

Fred,

I have a 3M. I got it at a local auto paint shop supply place. I don't know off the top of my head what particular model it is. I'm sure you can find it there. I do know that the filters pick up an awful lot of material. Also, I never blow any crap out of my nose, so I guess that's a good sign. Never experience any discomfort, like I've inhaled anything, so I guess it's working. I'm working outside, too, which helps. I have to do a little more research on heat shrinking and I may try it out this weekend. I still have a little bit of one door to finish stripping, the hood, front fenders, trunk lid and gravel guards. By then the weather should have turned for good and I can have some nice quiet time in the sun with my Evercoat and sandpaper. I do have some hammer and dolly work to do, which I am kind of just learning too.

[Jeff.P_46]

Hi Joe,

I bought a shrinking disc and also made one. It's definitly a learned technique. It works better over a rough surface were there's highs and lows, the high spots heat up and when you cool it they shrink. I think you would be better off using the torch just do dime size areas to cherry red and quench them.

Jeff

[Joe Flanagan]

Thanks, Jeff. This area is about the size of your hand, maybe a little bigger. It's dented down. Where would be the best place to apply the heat? Low spot? Around the edges? In the video, the guy was just kind of moving all around the area and it seemed to take all the flex out of the metal. It was pretty interesting to watch. I also wonder what is the worst thing that could happen (aside from setting my car on fire). I suppose you could worsen the situation by causing warping.

[Jeff.P_46]

I would start in the center and just see how it goes. You can also make a slapping spoon out of a mill or basterd file, push up on the area with a dolly, piece of wood etc... and slap the area. The ridges of the file create small valleys in the metal which take up the excess metal. A poor mans shrinking disc can be made out of a worn out 7" grounding disc, you just need something that will cause friction.

Jeff

[BobT-47P15]

I shrank a pair of pants once in the dryer.

(sorry, couldn't resist)

[Plymouthy Adams]

I shrank a pair of pants once in the dryer.

(sorry, couldn't resist)

you sure it was not a few hamburgers and a couple six packs between putting them in the wash and momma putting them on a hanger...

[dezeldoc]

If you have never done heat shrinking pratice on an old fender. it can turn into a can of worms real quick, espially on a roof. You need to hammer the metal into the center of the heat spot then quench the spot but not to much or fast as it will pull bad.

[Joe Flanagan]

Thanks. That's exactly what I planned to do. I have some old doors that are too far gone and are going out in the trash. I'll put a dent in one of those and practice. Still can't seem to find good, clear guidance on how to go about it. Meaning where to heat first. I'd prefer not to do any hammer and dolly work if I can avoid it because I'm not very experienced with it. I'm just going to experiment with a guinea pig and see what happens.

[Plymouthy Adams]

I recomend a shrinking disc to anyone wanting to shrink metal..these things are great and work twice as good if you have access to both sides of the metal...work the highs on both sides..there are no lows...lol

[wilmot andy]

I made a shrinking disk, and used it and have used a torch on the roof and hood of my truck. I couldn't believe it worked. Took some practice, sometimes seemed to chase the 'oil can' dent.

[Plymouthy Adams]

I made a small one from a 3 inch disc I found it has proved to be a decent device in tight places...

[dezeldoc]

the disc works good on smashed up fenders and such but won't work on a oil can on a roof. you need a torch shrink job on them.

[Flatie46]

I've never tried it, I watched it on tv and have heard of people doing it. I would think that it would harden the metal when you quenched it and might be just the thing for the oil can problem but I agree with trying it on scrap first.The roof on my car will need some one on one time with the tools of the trade also.

[Joe Flanagan]

If the weather holds up tomorrow, I'll be practicing on a scrap door and I'll let you guys know how it goes. I don't know if I can get a dolly to the underside of the roof and still hit it with a hammer where I need to. Dezeldoc, why do you say you have to use a torch on the roof?

[Rodney Bullock]

Hey Joe I got to see that can you call me just before you start:)

[Joe Flanagan]

Will do, Rodney. Let's see if the weather holds up.

[dezeldoc]

Pratice on that door and you will see why. roof's are easy to make a tincan out of. you might be able to take a pic hammer and gently tap it in the center of the dent after you get it where you want it and then hand file down the dimple and it will take the tin can out.

[stellarrestorations]

As for "where do I start with the heat", locate the center of the stretched area by flexing the oil can back and forth and looking for the perimeter of the area that is moving. You can mark the perimeter with a sharpie to get a visual idea of where the extra metal is.

If it is a light oil can and in a relatively low crown area, a very small amount of heat may be all you need. Take your oxy-acetylene torch set at a neutral flame and make a small heated area about the size of a dime that is just blue; not red; exactly in the center of the oil can. You can quench it with a damp rag afterwards if you want. Depending on the amount of stretch and the amount of crown, you might not even have to strike the metal with a hammer and dolly, it may tighten up on its own.

Mild steel should never be quenched while it is cherry red.

If that isn't enough, you can spiral out from the center with more heat spots.

Mild steel, when heated and allowed to cool shrinks as a natural result of the heating/cooling process, so take it easy. The less crown, the easier it is to spread the damage if too much heat is applied.

The shrinking disc works extremely well on low crown areas; it is much more controlled heat, but requires a grinder that turns 5-6000 rpm to work efficiently.

[Joe Flanagan]

EXCELLENT. Thank you. I'll refer to your post again just before I start. Will Mapp gas generate enough heat to do the job or do you have to use oxy-acetylene?

[greg g]

I had some luck on on of my studie fenders using a heat gun made for paint stripping. Heated the area outside of the dent, the used a bucket of water and rag to provide the cooling. Worked pretty good and no open flames to worry about. Wear safety glasses, sometimes the rusted stuff will pop off, kinda like grease spatter whe fryig bacon.

[stellarrestorations]

EXCELLENT. Thank you. I'll refer to your post again just before I start. Will Mapp gas generate enough heat to do the job or do you have to use oxy-acetylene?

I actually don't have any experience with Mapp Gas, so I should defer. What I know of Mapp Gas is that it comes in a bottle like propane, and fires a large flame similar to the hardware store propane bottle. I understand it to be hotter than propane.

I would assume "yes", you can use that kind of flame, you'll likely have more "periferal" heat generated in the area because the blue heat will generate slower than it would with the oxy-acetylene torch.

I would say "go easy"; it's easier to do it again, or "do more", than it is to wish you hadn't quite done that much.....

[Joe Flanagan]

Got it. Thanks.

[stellarrestorations]

Oh, it occurs to me that I like to shrink stretched metal while it is "up", rather than down like a dent. If you can bump it up and get it to stay there, that's where I would begin to work it.