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Old 12-04-2006, 10:41 PM
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Trying to bondo an "Oil-canning" panel

I'm not sure of the true correct techincal term is,.... "oil-canning" is what I call it..... When you push on the metal and it goes 'Bloop-Bloop', in and out like an old oil can.

Obvoiusly you can't bondo over this because the highs go to lows and vice versa. How can I firm up the metal ?

I don't have a shrinking disc, it sounds like it may do the trick. Not sure though. will it?

I do have a Stud welder for pulling dents...will this work? if so, do I stud weld the Highs? or Lows?

For reference. This is old Subaru van I am restoring. The Asian factory metal is very thin, probably 22 ga. ( unlike thick metal USA cars ) This "oil-canning" problem is in only in a couple of spots, { thank goodness } , one spot had prior accident damage repirs on the pass. door, about 6" dia. , I can sort of get behind it....but, not real easily.

The other spot is the tailgate. Impossible to get behind.

Both spots are very visible.

I'm nearing the end of my body work, but I've left these spots till the last trying to figure out how to deal with them.

Thanks,

Mark

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Old 12-04-2006, 10:49 PM
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They make a shrinking tip for the stud welder. I have one and it does work. But it will put a little dent where the tip hits the metal. I am thinking, though I have never tried that if you just put the tip you have up against the metal and pull the trigger it will heat the metal without the tip sticking to it.You then just cool with compressed air or a squirt bottle with water in it.

Brian
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Old 12-04-2006, 10:55 PM
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The metal has been streched and why you are getting the "oil can" effect.

Shrinking metal is an art - but there is no reason not to jump in and try it out.

Since you have a nail gun already if the area is not to large you can use the gun without a nail to get a small area hot - just act like your welding a stud - or like Brian said they make shrinking tips too.. hammer around if needed and then quench the area with water.

If the area is large - it will be more difficult. I've never used a shrinking disc, I usually use Oxy.Act torch. But I know with either of these tools you can really mess up a panel if you are not careful or don't know what you are doing.

Also do a search on the Forum posts in the body section - I'm sure the procedures for shrinking metal have been outlined within several posts...

Good Luck
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Old 12-05-2006, 01:38 AM
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Sometimes a wet rag as you go pin by pin, or without a pin in there but carefull on thin metal it will burn a hole if left trigger on to long ...


See more --> dents in side of surburan
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Old 12-05-2006, 08:20 AM
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Get a shrinking disk fom John Kelly, He had them "on sale" and you'll get it in 2-3 days.
I got one recently and it's the sheet for sheet metal.
You can also use a locking DA in the grind mode with high grit paper like 1000 or 1500 which will smooth instead of sand as well as create some heat. I use this on aluminum as well as steel with good results before getting a shrinking disk.
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Old 12-05-2006, 09:09 AM
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Thanks for the kind words Bee4Me!

Here is something I wrote a while back about oil cans..with a minor edit or two:

What helped me work with oil canned panels is to address the perimeter of the panel first, and work your way into the middle. Think about the tension in the plane of the metal, and the smoothness of the surface working together. You must make the panel smooth to read it. If this means making it have a little too much crown in it, so be it. You can easily shrink it back down. The crown a panel has puts just the right amount of tension in it to hold it in place without being so floppy as to pop in and out. Try pushing in on various spots around the perimeter of the area with your thumb while popping the oil can in and out. Once you find a spot that helps stop the oil can popping, check this small area for smoothness. You may need to hammer and dolly to get it back to a smooth but slightly high condition, then shrink to get the tension just right. There may be several areas that need this attention. It is easy to overlook a spot that is affecting the panel and spend too much time playing with the oil can itself. You can also try pushing out instead of in at various spots on the panel to see the effect on the oil can. If you are going to use a torch to shrink, try heating the metal to blue (or less) instead of red. It will shrink with very little or no hammering, and stay a bit more workable than metal that is heated to red. A shrinking disc is the best way to shrink an over-stretched panel because it heats just the high spots without over-heating them. You can stretch with the hammer and dolly and shrink with the disc many times without damage to your panel until you get it right. This allows you to free yourself from worrying about over use of the hammer and dolly which can keep you from getting the job done.

Oil cans can be very tricky. I recently spent about 7-8 hours fixing one on a quarter panel that I had flared. All the stretching of the fender had resulted in a different pull and tension in the panel, as well as a reverse curve that was not part of the original quarter panel. I ended up shrinking metal that had not been stretched to remove a large bow that inhibited the reverse I wanted, stretching various areas around the oil can, and pounding from inside the quarter panel against the inside of the door opening flange just a little for tension in the plane of the metal. The bow actually shrunk down 3/16" measured in the middle of a 20" verticle template of the curve before I started. I learned a few things on this panel that made it well worth the effort. Hope this makes some sense!

John
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Old 12-05-2006, 02:34 PM
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Mike where do you order one from.. I am going to get one, (its about time) and use it.. I have always used a torch to shrink metal, and never wanted to spend the money on a disk.. Its Christmas, so........
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Old 12-05-2006, 04:08 PM
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I am so happy just using the disc to shrink let along any metal finishing. I have a 2006 Mustang in my stall right now, pretty nasty dent in the quarter. I was able to push it out from the inside but ended up with some high spots and an oil can. Ran over it with the disc, tight as a drum and so close just a skim coat of filler did the trick.

It didn't have very good access from the rear so metal finishing would have taken way too long in the collision shop. But for just simple shrinking prior to filler it is like magic.

Brian
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Old 12-05-2006, 07:19 PM
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I am not even sure if htis is remotely a good way of getting rid of tha effect. But I pushed the area out from the rear, by applying light pressure, then tapping around the out edge of the canning area, from the opposite side of the pressure.

It seemed to equalize the pressure throughout the whole area. I have never done work this extensive, but so far it is working.

BTW: I am am way wrong in my technique I do apologize, but it worked for me, and a torch would have caused more probelms then cures.

Let me try to post a pic of the area I am working with.
It tin canned real bad just below the body line on the door near the front. You can see the looping mark that outlines the lower part of the worst area.



PS that is not me in the pic!

Last edited by armysniper; 12-05-2006 at 07:25 PM.
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Old 12-05-2006, 07:37 PM
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Hey, that's a cool Impala, looks like it hasn't seen battle for quite some time, barn dust all over it! The door is repairable and part of the proceedure uncludes doing exactly as you did-pushing the low area up and tapping those high eyebrows down. But do yourself a favor and purchase a shrinking disc, looking at the metal work that that car needs you'll be many many hours ahead of the game and end up with much better results.

Within that damaged area on the door are areas that a stretched, the metal had to stretch in order to accept the dent and change in shape. You can hammer and dolly all you want in an effort to get the metal back to the right shape but if the stretched areas aren't shrunk down it'll never return to it's original shape. If you knock the stretched areas out and run the disc over them to heat them up then cool fast they'll shrink and tighten up-hope this makes sense. Oh and yes definately a torch can be used to do the same thing in the hands of a skilled metalman-it's been done for years but requires more skill than a disc. Good luck on the project! Nice old iron for sure. Bob
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Old 12-05-2006, 07:44 PM
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I bought the car sept 12, The car sat under a carport for 8 years. I 've been doing a few things here and there, and lately most of my time has been crankin on the body. I have actuall already fixed 90% of the damage, betweent he dents, putting in new floors, and cutting out the rusty areas, I am nearly complete with the body. I have sprayed a few coats of epoxy and a couple coats of high build. Been blocking for awhile now.

I can post the after pics tomorrow if your interested. Maybe you can give me some more hints, tips and tricks if needed?

Threadjack over, you can now continue along in your regularly scheduled program!
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Old 12-06-2006, 11:22 AM
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BK, Just PM John here or check at Metalmeet and he'll get with you.
He recommends using a 6000 rpm grinder with one but I've had a hard time finding one at the speed which ain't a million dollars so I just use my old buffer which runs around 3500 on high and it's done most everything I've tackled. I tried a Mikita I have but it's 10,000 and WAAAAY to fast for one.
I used it on the hood after pulling the dents back up which were over the back main brace with a stud gun as well as a few high spots from reattaching the bracing and it took them down beautiful. Sweet tool.

Think this is it.
Ghia
Mike.

Last edited by Bee4Me; 12-06-2006 at 11:27 AM.
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Old 12-06-2006, 12:09 PM
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Brian Martin,Freelance adviser
 
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Mike I got a 5000 rpm 15 amp Milwaqi (I can't for the life of me remember how to spell that) that is awsome. It was recommended by the guy I got my shrinking disc from. Hopefully John Kelly will chime in on that. I wonder if the 5000 rpm is really needed.

Armysniper, you are refering to the "off dolly" method have hammer and dolly work and it DOES "shrink" or "gather" metal.

Brian
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Old 12-06-2006, 03:08 PM
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Hi Brian,

I've used 3400 rpm and 5000 rpm machines to shrink. I've been told of a guy using a 1750 rpm machine to shrink.. The lower rpm ones just take longer, but on the upside they are cheaper and weigh less.

John
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Old 12-06-2006, 04:07 PM
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A big AMEN to that John. That 15 amp mutha I have wieghs a ton and will really give you a work out. And being it has so much torque it literally wants to twist out of your hands. It's a muscle builder thats for sure.

Brian
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