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Shringer disc.

4K views 26 replies 8 participants last post by  tech69 
#1 ·
I've got a 62 chev that I'am doing a paint job on. Going to be bright red. The hood on both sides from the two center humps that run the lenght of the hood to the outer edge feel like a roller coaster.I know I have more metal than needed and somehow I need to shring it. I have never used a shringing disc but do you thing this would be a good use for it. I really hate to work it with heat and fill the hood from end to end.
 
#3 ·
shrinking disc.

If you haven't used a disc, get some dumpster body pieces from a body shop and practice. If you click on the search box without entering anything you will get the old search function, go to the bottom of the page and click on deep forum search, then do the search for shrinking disc and you will get several pages of old posts about using one.
 
#5 ·
they can be troubling on hoods and decks due to the fact the skin is adherred to the shell. It can effect where the metal goes so light shrinks is ideal. If we're talking just looseness that needs to be tightened I like to hit the corners/edges with a dinging spoon to tighten up the arch first. It works pretty well. More than anything, a hood and deck as we all know usually provides an arch that provides stability to the big open area of metal between lines and edges, and this is what also makes them harder to deal with, besides the fact you got a huge shell clinging onto it. What I've realized it's best to cut away the skin from the shell before shrinking it, and to as always, do really good metal work before getting out the disk. Just be sure to distribute the heat in a broad area as opposed to putting too much heat in one area. Also, you might like to keep your disk clean with 40-180 grit paper by hand. Some people would be against it but I think the scratch 0f 40-80 grit makes it heat up faster and it's easy and fast to clean it up. Some people warn against sanding them clean but I don't think it's a big deal.
 
#6 ·
Very good points Henry, a wavy large panel is a lot more than just running a shrinking disc over it. I haven't a bunch of experience with the shrinking disc, I have one, have done some pretty amazing things with it, I am VERY impressed with what you can do. But I would be VERY cautious about running it over a hood.

There are so many things that could be at play here as you pointed out so well.

swvalcon, here is a "Basics of Basics" on large flat panels, there are a number of other things to think about before hitting it with heat as Henry points out, check it out. Large Panel Repair - Autobodystore

Not saying that anyone is wrong, Pugsy knows more about metal fabbing I could dream of. But just from a repairers point of view, with average skills, that is how I am seeing it. Read the basics and there may be something there for you as well.

Brian
 
#7 · (Edited)
yeah, for waves and stuff it's not really good, especially if it's adherred to the skin. Everyone knows hoods especially are hard to shrink with excessive heat in localized areas and the problems venture outwards til you're scratching your head and the entire hood has gotten shrunk, so this means a shrinking disk is definitely the tool you want to use but you mainly only want to use it for tightening up the panel, in which you're better off using the disk in the corners to tighten the overall flex of it but to also use it in the traditional aspect of "metal work" shrinking(not solely just flex of it) more along tighter areas where the metal is tighter and easier to work with. The more you venture towards the middle of the arch the better the metal work has to be in order to not get adverse affects. It's my opinion that the disk is best useful when using shot bags and planishing hammers or something equal to it but for hoods to go light and kind of keep it close to tighter areas and more careful in looser open areas. For quarters and tighter areas they are much more forgiving for the user.

one last thing, the disk is at its best when you have easy access to both sides of the panel so you can break out the bean bags and mallets
planishing hammer or equal to. without that it's much more difficult to get the results needed to truly get any value out of it, and so with that said,
I find it easiest to use it sparingly on hoods/decks cause it can reek havoc on hoods that aren't fully worked.
 
#9 ·
I just went ahead and did some hammer and dollie work on it and put a thin coat of mud end to end. If it dosen't hold up he'll have to find a new hood. He sand blasted it and thats what ruined the hood. Any where he hit the underside of the skin it pulled the skin down and made the top panel waves.
 
#11 ·
those are the worst and hardest to detect. In other words, the small areas that are adhered to the shell still give it the arch it needs but what surrounds sags. Those are absolutely the hardest to deal with and are a headache.

We just had a new year one hood and it looked great coming out of the box. It was exactly what you are describing but new, if you can believe that. It got mud almost covering the entire surface and primed twice....keep in mind this was a brand new hood.
 
#14 ·
LOL,customer says...... I got a brand new front end on my 69 camaro ....IT'LL BE EZ TO PAINT....HOW MUCH.....HUH,1500.00 ??????
dont do any bodywork just paint it...
Body shop....bring me the pieces and I'll paint it for 300.00
Customer....Sounds like a deal
two weeks later......customer says.... hey remember me ? you painted my camaro nose, well can you get it bolted on and painted again?????
WHAT!!!!!! 3,000.00 but you said 1,500.00 before I screwed it all up......
 
#17 ·
Your right,They just dont know,they think its brand new so its perfect...so insted of argueing with them you have to school them and most learn best when it hits their wallet...
After market fenders and panels NEVER fit well ,they ALWAYS have to be persuaided to fit...
.Newer cars are a different story they have a pretty acceptable fit right out of the box,not perfect by any streach just acceptable.
any way you look at it if you want something that'll last you'll have to strip off that black primer and put your own on because that stuff is crap and its so thin its all but useless...
Heres a shot of one of the best hoods I ever got from goodmark ...after grinding and sanding all the sharp edges(top & bottom) some delicate hammering and dollyingall it took was two coats of EZ sand putty to fill the waves...only took about 8 hrs to get in the booth....
HEY, a 69 camaro hood ,what do ya know....
 

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#16 ·
Remember years ago I made a bid on a buick 1/4 panel for a guy. Just a normal side scrape. He comes back a couple days later and say's I need a new price I fixed half of it. Well he had beat the crap out of it with a bfh and made five times the work it was to start with. You should of seen how pisssed he was when I told what he had done and told him now the price was double what I had given him to start with.
 
#18 ·
Man I run into that all the time.the last one my friend used his sissor jack to push his 1/4 out because he saw me doing it a few times and it looked EZ...
OMG,he pushed it out o far you could actually see the shape of the jack head in the metal... to say he streached the metal would be being nice,I had him look down the side so he could see the 6" buldge sticking out and until then he thought it was great...I couldn't resist telling him to be careful walking passed it if he hit it with his knee it would be like walking into a trailer hitch....ouch......
I fixed it up but made him promise not to do bodywork ever again. if he wasnt a good friend and already brought me his last five cars to paint I would have sent him down the road for sure...
 
#20 ·
paint type.?

I've stripped the paint first. My first Model T roadster still had the 1916 Ford paint on it, when I started sanding it off years ago with a 1/4 in drill with a sanding disc, the paint just melted and started flowing like I was melting plastic. I worked on the hood of the old 1951 tractor but the paint was 95 % gone, and it still takes a long time to work it out but I was using a 5 in disc made from a SS plumbing clean out cover I bought at lowe's . Metalmeet forums show how to build one for a 7-9 in grinder. sometime I'll try for a big one.
 
#21 ·
"...Can they be used on paint or do you have to get the paint off first before using one."

You need to take it to bare metal AND some area larger than you are fixing. the paint will melt, make a mess and act like grease to stop the disc from working. They work great, you will ask yourself why you waited so long to get one.
 
#25 ·
shrinker demo

I saw one demo-ed at a car show about 15 years ago. one of the guy's watching said let me try that, He didn't have any sucess. so I walked on by, and didn't get interested until a couple years ago reading on Metalmeet forums on how to build one. It takes some technique. it works similar to using a torch to heat up a spot, hammer it down on dolly then cool with a wet rag to shrink it down.. The spinning disc against the body creates heat and the high spot expands up, you apply pressure to push it down , similat to using a hammer then lift and let the air swirling from the disc cool that spot to shrink it. and use a wet rag to take out the residual heat that spreads from the hot spot. It takes some technique to know how long to hold in one spot to create the heat, how hard to apply pressure and then to spin cool it.
 
#26 ·
I like to refer to the disc as a "Heat block" it heats only the high spots and you cool them to shrink them. Like I said I am no pro but when I was using on every day when I first got mine I was blown away at what could be done with it. Wish I had photos, one Toyota quarter panel I did was absolutely amazing. The metal was folded over it's self at the rear by a glancing blow with something very solid. The damage was about 18" long with this corner being folded over with about an 1/8" radius fold hanging off the quarter under the tail light. I got it all back into shape with only a few coats of primer, it was WILD.

I got mine from Ken at Sun Chaser tools and bought his 5000 RPM grinder and was never sorry. I would use it for collision work on big bondo jobs like the bed side of a truck or something just to get it tight for bondo. It worked great for that, I could of repaired it with no bondo but being there just ins't time, I would use the disc to tighten up the oil caning panel for filler.

Here is a review I did on a DVD I got from John Kelly, it doesn't appear he is in business anymore but the into on the disc still stands. http://www.hotrodders.com/forum/ghia-specialties-metal-working-video-review-115471.html



Brian
 
#27 ·
they are very good for bedsides cause it's a big open panel. If you use something not as good as a shrinking disk you run the risk of overheatting it in a small localized area which then borrows the metal from somewhere else and you'll create a loose area adjacent to it. Obviously, using a stud gun you can easily get away with it by doing lots of light shrinks but still not as accurate at distributing heat like a shrinking disk, just faster.
 
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