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shrinking sheet metal


Guest grandpas1936

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Guest grandpas1936

I've been working some of the dents out of the cab on the truck before I seal it. One area in particular took quit a bit of work and now has stretched to the point where I will have to shrink it.

I've seen all of the methods and will probably go with the heating and cooling with a rag method.

My question is, rapidly cooling will shrink it but will also harden the steel. If you heat and let it cool slowly after this, will it restretch it? This should help stress relieve correct?

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Guest palosfv3

Shrinking metal takes quite a bit of expierience in metal straightening. There is a lot of trial and error in the learning stages before one finally gets comfortable in understanding if the panel is stretched and how to identify a damaged area , how little or much heat may be necessary to shrink an area, how much or how little hammer on or off dolly work is needed before quenching, using a shrinking disc instead of a torch, ect . There is just a lot involved. I dont mean to discourage but most metal people I know have destroyed the first several panels they tried to shrink. Trying a couple of practice repairs on some other less valueable panels may be beneficial.

I'm posting a link to a search done on the subject of shrinking from the Metalmeet Forum. This is where all the metalshapers both pro and amateur hang out on the internet. Read through several of these threads . You should find them helpful and the guys are eagar to help.

http://metalmeet.com/forum/forumdisplay.php?f=167

Post some pictures of your damaged area. Be aware that many damaged sheetmetal panels are displaced metal more often than stretched metal.

Edited by palosfv3 (see edit history)
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To answer your question - no, you will not harden old body steel by quenching from red heat. The low carbon content will not allow this to happen. Hardening only occurs with high carbon steels. Not sure about modern high tensile body steels - these may require specialised treatment.

Heat shrinking is a valuable skill to learn. Stretch some scrap steel and practice using small heat areas - no larger than 3/8". Hammer the surrounding stretched metal into the red hot area using a flat backing dolly. Quench with a wet rag just as each heat loses its red colour.

Work around the centre of the stretched area and gradually outwards.

Work slowly and use your hand to feel the surface as you go (after quenching of course).

Take it easy and you will be rewarded with the satisfaction of mastering a traditional skill which produces impressive results. Then you will want to learn lead loading.....

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Guest grandpas1936

I've been working with an old fender I had for a few days and must say it is very rewarding when you finally understand how it works. I am ordering a shrinking disc this week to see if it helps. I have read a lot on metal work and am beginning to enjoy it. It seems that this is on the border of becoming a lost art.

@TonyAus: Good point on the carbon content. I had not considered this.

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