streatchin and shrinkin?????

I need some advise on shapin my roof skin on my 78 chop top ???
I am ready to weld my roof skin on and i usually mig weld it and hammer it into shape as i go[while it is still hot].And i already figure it will get some big oil cans in it and i dread fighting with them because the sheet metal is so thin on these newwer tops .there allways harder to work into shape.
So i wander how some of you guys deal with oilcan spots in larg sheetmetal panelssutch as roof skins or door skins?
I have tryed a lot of differant things over the years but still fall back on a tourch tip and a rag in ice water as a last resort [and i'm not too good at that either,just learned by exspermenting with it].
I have been thinking of buying one of those hammers with the swirl in the face to shrink with and mabie a stianless steel grinding disk [from eastwood]and would love some feed back from some of you guys that have used one befor? O r some tips and tricks that you can give that may help ? Thanks in advance!!!

Tom, I've used a stainless steel disc in a sander/polisher to remove oil can from flat floor panels. It worked fine but took about a half hour of effort on each panel. A more powerful, faster grinder would have made more heat and probably would have worked faster.
When we welded the top back on my grandson's GMC (he's Zacho on RRR) we got 4 very deep sinks (dents) in the roof. I tried to shrink them with a torch and wet rag and got nowhere. Just seemed to harden the metal. Finally, I realized I needed to stretch the sheet metal to change the dents into the crown the roof needed.

anyone tried using this heat sink putty for welding ? , i`ve used it for a/c repairs on copper tubing and it works great for that http://www.eastwoodco.com/jump.jsp?itemID=1616&itemType=PRODUCT

use very small tacks, and move from one area to another to keep things cool and avoid warping, and cool your tack welds as you go...

dawg said:

use very small tacks, and move from one area to another to keep things cool and avoid warping, and cool your tack welds as you go...

Click to expand...

Thats the way i always do it and hammer and shape it as i go but on something with such a wide open span i still ussually get an oil can or two that wants to pop up and down while doing body work [can be very agravating]
I wana learn more about shrinking the metal to draw it tight inorder to aid in doing the bodywork . Some times i'll use a pick hammer and then grind the piks out when i do the bodywork ,and it helps but i could use less filler if i could master shrinking it and leveling ?

a heat shrink can be done with a small neutral flame. Heat a dime sized spot near the middle of your oilcan to cherry red. (IMPORTANT NOTE) The spot you are heating must RISE!!!! If it starts to sink, STOP! Once the spot is nice and red, use a rag soaked in cold water to quench it. Change the water in your cup often as it will get warm rather quickly. Let the area cool completely before doing another. Once you have done this the area will be work hardened and can be metal worked but not metal finished. It will need filler. It may take several shrinks to remove the oil can.

I use my stud welder without a stud, to shink in the same manner. The only thing I would add is to sometimes bump the heated crown with a broad or flat faced hammer. Should you find it necessary to soften a work hardened area, you can aneal it with your torch. Light a heavy carburized flame, and let the black birds soot up the area yo want to aneal. Then, with a neutral flame go back and warm the metal til the soot is just burned away. Let things cool down on their own and it should be workable again...

With the torch,you don't even need o heat until red before quenching.

The shrinking discs are supposed to be very good.
How much does Eastwood want for one ?

Also check out the Metalshapers Association site for more info http://www.allshops.org

shrinking

way i was taught was to heat a spot red and use a dolly block underneath and body hammer spot and quench w cold water on sponge sometimes you have to put many shrinks in a bad spot like on a high crown 0r go back and repeat

spend some time planing and useing a straight edge looking for low spots and use your hands to find the bad spots, know where you need to do the metal work, take a magic marker and put x 's where you need to put in shrink spots so you hit the bad spots right on

Thanks guys for all the input !I do really apreciate it.
I have ben shrinking with the quenching methode for some time now and it works ok but seems a little out of controle at times.
Heres a tip that you guys may not have tryed yet ? Try useing an ice cube instead of a rag in the dime sized spots when you heat them ,it worked really well for me ,even when i was a sawfiler i tried it whith some good results!
I was hoping to hear that some of you have used the swirl faced hammer before and some good news on the stainless disc's too ?
I used to have a rod and custom mag that had an artical on some thing called the wander disc [i think anyways] [this wavy looking thing,used on a ginder]that they esed on a project 53 chevy ?Have any of you seen or used this with any good results????

It will work, but the main thing you need to remember is that shrinking should be done on a localized area(s). When you shrink, you should use off dolly hammer technique. I.E. the metal being shrunk is the portion BETWEEN the high and low spot. What you are trying to achieve is getting the metal to gather, which is what causes the work hardening. I only use one type of shrinking hammer. It is sold by Snap On and has a wide face with many small "peaks", or a stippled face on one side, and a smooth wide face on the other. The peaks allow the metal in between the contact to gather as it is being bumped. Again this should all be done off dolly, on dolly tecqhniques are reserved for stretching. Should you find it necessary to back up the panel while shrinking, try using a block of wood instead of a metal dolly. I even have some made with different crowns, and wrapped in leather, but these are used for serious metal finishing only. As for the wavy disc, it is used mostly for finishing, after all the pick and file stuff is done. I get the same results from a well worn 7" grinding disc. The wavy disc is cool, but it isn't really meant for serious shrinking. A well mapped plan for the surgery you are doing will keep most warping issues to a minimum. Take your time and move your welds frequently, avoid trying to make long welds as much as possible. And if you screw it up, just fix it, after all it's only metal...

I have both the stipple face and the swirl face hammers. The stipple face works best. Like Dawg said, you use a glancing blow to "gather" the metal. The swirl face is adequate for small areas, but i sub-par at best for anything else. It basically does the gathering on a straight blow, just not very effectively.

hammer

I just use a round convex Proto hammer start outside and tap in circular motion and move to inside as you go
for someone who has not done this take a junk door or hood or something smash a dent in it w a sledge and practice and invent your own favorit method and try the many methods talked about above, something is bound to work, its better to ruin junk junk than the part that is irreplacable and has to be saved for your precious car, and all old tin is getting scarce quickly nowdays so learn metalwork and save it

thanks again guys for all the support and imput !!
I do good work as is but am wanting to take it to the next level and want to be able to not have to use filler some day on a big project but it seems that as long as bondo is avalible i'll always need it .
I will say that making my self an engish wheel and useing it,has opened a new level of metal work over the past couple of years and i love useing it ,it can be a lot of fun and supriseing what one can acomplish with it !!
Are the big vixon files worth the money?

Those swirl faced hammer remind me of a meat tenderizer.


Check out Allshops.org for more info on serious metalworking.