Heat shrinking steel questions?

[sport]

I was just wonderin' whats the best way to go about this?I have a 37 pontiac that the roof is all caved in, so I hammered and dollied it out .It came out really well, but there is one spot above the drip rail that is streched pretty good and needs to be shrunk.I don't have a shrinking disc.So Í need some guidence Thanks.

[Unkl Ian]

To shrink,you need to generate some heat.First choice is a shrinking disc.I've heard of people using an old grinding disc installed upside down,but I've never tried it.Second choice is a torch.Don't get the metal red hot.Blue hot is good enough then quench with a wet rag.It's a slow process,but it does work.

[SwitchBlade327]

the way i was taught was to tae your torch and heat the center of the stretched area (in a circluar motion) until you have a red spot about the size of a dime, and with you body hammer hit the metal (not very hard) in a sweeping motion towards the red dot, do that 3 times from different sides of the red spot, then tap it once right on the red spot. Immediately put a damp rag on it to cool it off, you should be able to feel the metal shrink under the rag. This mgiht not make much sense but it's hard to explain just in words. This is how i fixed the quarter panel on my poncho, I had to shrink it 7 times it was so stretched.

[TV]

If it were me I would invest in a disc.I've done both and for a roof the disc is by far the best--TV

[sport]

SwitchBlade.I think that's bassically the way I was taught along time ago .It's been so long.I needed a crash coarse.But I forgot about the sweeping motion with hammer.

[cadlights]

Switchblade's got it, I did it that way for 35 years.
The secret is not to qwench it to fast, let it cool just a bit before qwenching,a rag works real good.

[roadster36]

If you are new to working out stretched metal it might be best to NOT use any water to quench the spot you heated and hammered. I heat the spot to a straw color or a little beyond, NOT RED HOT. Start with very light hammering from the outside working towards the inside in circular pattern ending up directly on the center. GO SLOWLY and check your progress. Beginners often make the problem worse on the first few attempts.Stay away from quenching if possible until you get a feel for how the metal works.Hardened metal is always more difficult to work back into shape.This is one of those things that "reading about it" doesn't get it. Fire up the torch and give it a try. I bought and use a shrinking disc, but I did so only after I mastered the art of shrinking with the torch.Good luck, it's a great feeling to have it come out the way you need it to.

[Scott B]

I need to take care of the same thing...

What does the hammering do, after the heat - other than apply some molecular metal mojo?
Are the hammer blows to the convex or concave side of the dent? Are you striking into the dent, or pushing it out, in other words.

Where can I get one of these shrinking discs? Metalshapers, maybe?

[Tinbender]

I shrink much the same as roadster36, however my first strike with the hammer is in the center of the hot spot. This pushes the metal that has expanded out into the edge of the heated area, thickening it. Most of the shrinking happens with that first hammer strike. It takes very little force. I then support the area from behind with a dolly and very lightly "on dolly" hammer, to smooth the area. I cool the metal with compressed air, not water. Practice with some scrap panels, and try the methods mentioned here. It's not that difficult, but you can damage the panel if you get too agressive.

[Reverendcolin]

Is Sunchaser Tools still around? There site was a little screwed up when I just searched. Like it wasn't really working anymore.

Someone else must be making the metal shrinking disk by now. They were about $250 last I knew (a while ago). Any info on this?????

[Scott B]

Tinbender - I don't completely understand...hehe.

That first strike with the hammer, in your process, on the hot spot - are you hitting into the dent, or are you coming at it from behind? Or does it even matter?

I get that things are shrinking with the cooling. I get that you are hammering on-dolly to keep things smooth. I even get what the first smack is doing, so I guess, well, yeah...

[Shiva69]

Hey Rev check out metalmeet.com. you'll have to sign up but it is a good resource. they have a post on the forum of how to build a shrinking disk... and also on metalshapers.org there is a picture album about one as well
and John Kelly on here makes them and sells them for i think 50 bucks.

Garth

[Unkl Ian]

Another source for info: Metalshapers board (http://groups.yahoo.com/group/metalshapers/)

[Shiva69]

Thanks Unkl ian.

Garth

[CharlieLed]

John Kelly, his name and his HAMB handle, fabricates and sells shrinking disks. I bought one from him last year and I am very happy with it...

[Tinbender]

Dusty nuckles,
Most of the time stretched metal is in the form of a high spot. (if it's an "oil can" area, and low, I push it up first) As you heat it it rises more. I strike the center (the highest part)first. This compresses the simi-molten metal making it thicker, reducing the surface area.
I made a shrinking disc as per John Kelly's "how to" post. I like it and recomend you buy or make one, but I still use heat once in a while. Just depends on the repair.

[ray]

yeah JK has the discs for $50 i think, i got one, i've been waiting for the harbor freight grinders to go on sale, they just did, so i wnet there today and they were not in stock, hafta check in a few days i guess, i'm getting anxious to try the disc out!

when i was young, i lived in a trailer park, and went sledding off the roof of a rusty old 54 chevy parked next to the old gas station nearby, run by the old man, Gus Mafuckinpolishnameican'tspell... and his bearded wife(really).

well, i think i was 13 or 14, coming home from the last street rod nationals in minnesota, when my dad decided it was time for my first CAR(i already had a old stude truck), SO. what car do we go buy? yep. that same rusty old 54 that i sledded off of a few short winters before!

at that age, it was beyond me how i could possibly get those creases out of the mildly dented roof! never had to deal with it though, found a cleaner 53 hardtop that soon got my focus...rusty but at least the roof was not dented http://www.jalopyjournal.com/ubbthreads/images/graemlins/crazy.gif

[Reverendcolin]

Thanks for the great info. Everything I ever wanted to know on metal shaping..

I checked out the build your own but I think for the $50. plus shipping....it's a deal.

BTW. Garth,
Great Avatar

[John_Kelly]

Thanks for the recommendations guys! Reverend Colin, Here is my album page. There are three separate albums about shrinking discs. Shrinking and shaping disc, and drastic shrinking are the two best:

http://allshops.org/cgi-bin/community/communityalbums.cgi?ownerid=9990093068868

Thanks, John www.ghiaspecialties.com (http://www.ghiaspecialties.com)

[Tinbender]

BTTT Thanks for the link John, I lost it with my last computer upgrade.

[roadstar]

I have a shrinking disk and I love it. I have to admit it is a slow prosess but very effective.
One thing I have to say though is you really need to understand what the metal does when you get it hot, as it cools, and what happens when you start to hammer and dolly it. Whether you are hammering on or off dolly hammering.
There is a saying "you have to be smarter than the metal" And that means knowing what and where it is going when you work it.
It's true when you shrink with a torch you will bring a small spot to cherry red and it will rise up slightly and thats the spot you want to hammer flat to compress the metal and bring it togeather, then cool it and tighten it up. But....too much hammer on dolly work will stretch the metal further and you will really be lost.
I can't emphisize enough knowing what the metal is going to do each time you do any thing to it.

The best advise though is PRACTICE.

[John_Kelly]

I find that the more I use the shrinking disc, the less I worry about overuse of a hammer and dolly. I use the hammer and dolly a lot, and am completely unconcerned about over-stretching. It frees me up to do my best work without anxiety. The hammer and dolly are under-used by a lot of folks because they are concerned about stretching. This can keep you from reaching your potential with the tools. I think of stretching and shrinking as if you are balancing on a wire. You go from one side to the other to balance. You do not stay rigid in the center. Makes it simple for me.

John www.ghiaspecialties.com (http://www.ghiaspecialties.com)

[Reverendcolin]

John,
Thanks,
Checked them out, lots of info.

I'm teterring on the idea of getting into some tim knockin for a car I'm looking at. Haven't done much in a long time. Does anyone spray lead anymore?

[roadstar]

John I know just what you mean about the disk raising the confidence level. It's almost like you want to over stretch the metal sometimes just so you can shrink it right down to where you want it.