[JUDGE3]

Began gap fitment on my doors today. going very well, except I made the mistake of thinking the solid wire and the door being strong on the edges as well as having plenty of "heat sink" holes, I wouldn't have to worry about heat and warpage.

another rookie mistake. I warped the new door skin at the bottom area, and even worse, it has a canning condition. mad at myself! nice door skins to!

how do I fix that? shrinking disc that I've seen folks talk about? will heating the area with a butane torch and then quenching it with a cold rag fix it? I don't want to make it worse using the wrong technique, I don't know if I need to shrink the metal, or expand it.

help is very much appreciated. I'm in panic mode over it.

[n20ta2]

Butane torches won't get hot enough to work properly I have a gas torch I use to get the area red hot then quench it. The gas torch heats the area within seconds rather then minutes with a butane torch, possibly causing more damage because the heat has a chance to spead to a larger area. Shrinking discs work well and are fairly easy to use, I have one I use from time to time. The heat is localized and easy to control just be aware that you will most likely end up chasing the expansion around the panel a bit.

[n20ta2]

FYI if you can get a hold of a body shop that has metal shrinker it may be worth it to pay them for an hr or two of there time to fix it. I bought an eagle shrinker from a body guy that was retired and it is awesome! Works like a welder with pinpoint heat with virtually zero panel damage just a tiny arc spot at point of contact.

[tininjun68]

Shrinking disc X2. I learned a little while at Wray Schelin’s Open House a few years back. He makes it look easy but it works. He sells discs too: https://www.proshaper.com/product-ca...hrinking-disc/.
Not sure how busy he is now but he’s a nice guy in person, teaches metal shaping/coach building at his shop in MA. You might be able to call and pick his brain especially if you’re buying a disc from him. Good luck, either way!

[JUDGE3]

Thanks

do you still quench with cold rags when using a shrinking disc?

[n20ta2]

You can, or compressed air. The wet rag will cool it a bit quicker.

[roger1]

I'm not understanding here.

You caused the oil canning using heat? Sounds to me like you need to do some planishing for stretching the metal rather than to apply more heat that will shrink even more.

[n20ta2]

Heat can expand the metal if it isn't localized and cooled quickly, if he has oil canning the metal has expanded to much and needs shrinking. If he expands the metal more he may get rid of the oil canning but will have a bulge in the door.

[JUDGE3]

diligently paying attention here. this is a learning thing for me, I have zero experience with this.

to explain....I was welding wire for gap correction along the entire bottom of the door. the heat caused warpage/canning above that area in the door skin. (sucks!)

been searching you tube for visual instruction. I see using a disc the problem is usually a high spot? the torch and quench on lower spots? is that right? also I see after a heat torch its smacked with a hammer then quenched. do I have to dent my new skins? ugh

I have full access from the backside of the door skin if that helps. maybe come in from the back?

[roger1]

Originally Posted by n20ta2

Heat can expand the metal if it isn't localized and cooled quickly, if he has oil canning the metal has expanded to much and needs shrinking. If he expands the metal more he may get rid of the oil canning but will have a bulge in the door.

I just have to disagree with you here. Everything I have read and everything I've experienced is that heating and quickly cooling always causes shrinking.
And welding on a panel is always followed up with planishing with a hammer and dolly or slapping spoon and dolly. And the best practice is to weld only a little at a time followed by the planishing in several iterations as the idea is not to let the panel get very far out of it's correct shape in the first place.

Oil canning can take place with either too much of a shrink or too much of a stretch. Too much of a stretch is where a shrinking disc really is helpful.

Also, if you have an oil canning situation and aren't sure whether it needs shrinking or stretching to correct, making the wrong choice is going to make it that much tougher to ever be able to get right. You end up with some spots over stretched and other spots over shrunk and no way to know what is what.

It's best to use the weld/planish procedure in an iterative manner to never get to the oil canning problem in the first place.

Anyway, that's my experience and my take and I'll be quiet now. I don't want to start an argument here. Just want to share my 2 cents.

[n20ta2]

Your right about planishing welds that should always take place if possible but how would over shrinking a panel result in oil canning? Expanding steel results in a warp in the panel (over expansion from concentrated heat in one area) resulting in oil canning. If you over shrink an area it pulls in and tightens so you wouldn't have too much material in that area. Whenever I mig weld panels I always weld small areas around the panel using compressed air to quickly cool my welds so it doesn't over expand. I still always have to end up shrinking the panel an inch above and below to tighten the panel to I don't have to use much filler at all.

[n20ta2]

OP post a picture of the problem area from the front and side view, that would be very helpful in determining your next course of action. I would also be careful of using extreme heat its really easy to over work a panel.

[roger1]

Originally Posted by n20ta2

Your right about planishing welds that should always take place if possible but how would over shrinking a panel result in oil canning? Expanding steel results in a warp in the panel (over expansion from concentrated heat in one area) resulting in oil canning. If you over shrink an area it pulls in and tightens so you wouldn't have too much material in that area. Whenever I mig weld panels I always weld small areas around the panel using compressed air to quickly cool my welds so it doesn't over expand. I still always have to end up shrinking the panel an inch above and below to tighten the panel to I don't have to use much filler at all.

Planishing stretches metal in the heat affected zone (HAZ) that has been heat shrunk from welding.
It depends upon the natural crown that the panel has. A panel that is over- shrunk can indeed cause oil canning just like over-stretched can. Been there done that and best to be avoided using the iterative weld/planish approach.
Since the OP has only welded at this point and caused the oil canning, next thing to is planish the HAZ area where he was welding. I think that may solve the oil can problem right there.
These are my opinions just from what I've seen him post but not being there to see it makes it hard to judge. But I maintain that if all he has done at this point is weld, it needs to be stretched and not shrunk more. Do the wrong thing and it might be near impossible to correct it. Seen panels ruined by this exact thing before. Done it myself in my earlier days.

[mrennie]

Originally Posted by roger1

Planishing stretches metal in the heat affected zone (HAZ) that has been heat shrunk from welding.
It depends upon the natural crown that the panel has. A panel that is over- shrunk can indeed cause oil canning just like over-stretched can.

This has also been my experience as well. All panels have a crown, either inwards or outwards, and when the crown is reduced (panel made more flat) it will oil can much easier.

In some cases, stretching the metal (depending on where it is stretched, say adjacent to a low crown area) may act to lessen a crown and increase oil canning. In some case (usually from welding), the shrinking of metal reduces the crown and increases oil canning.

[n20ta2]

He may indeed have low areas and thats where the pictures will hopefully come in and show whats going on. A wavy panel is not oil canned, oil canning by definition is a stretched panel that won't hold its shape. If the panel is pressed on in the affected area it buckles in and stays, if its pressed out from behind it buckles out and stays . In that process it makes a sound similar to the old oil cans they used to sell that you pressed the bottom of. That can only happen if the panel is stretched. Like I said its very possible the panel is over shrunk and the op just said oil canned without completely knowing what it is.

[n20ta2]

In my experience an oil canned panel will need to be shrunk in some areas and stretched in others but usually the stretching isn't needed as much just to fine tune it.
Been welding and fabricating for 25 yrs, maybe I was told the wrong way but its always worked well for me! I have a shrinking stretching tool, if you guys ever get a chance to use one you would be amazed at how awesome they are. I can clean up a wavy panel to almost perfectly flat needing little to no filler.

[PurelyGTO68]

I had some oil canning issues in the quarter panel. I corrected it by shrinking the high and low spots. I used my stud welding gun (without the stud inserted in the tip) to heat a small area about the size of a quarter coin and then cooled it with a wet rag. Worked great for me.

[n20ta2]

Nice! Yeah my eagle shrinker/ stretcher is basically like a mig welder, it has a ground and transmits heat though the tip. It has a different leed for stretching.

[JUDGE3]

hope these pics help.

the lower portion of the door skin BELOW the tape is the affected area. wave's in and out 46". its not a "can" in the sense that it go's pop in-pop out when pushed. the skin now feels weak and loose if that makes sense. by canning I mean that I can push the areas affected in and it will stay in, then I can push the affected areas out from the backside and they will stay out. you can actually see by the tape how much it waves in one of the areas.

I really appreciate the input. shrink disc? heat and quench? I hope that you experts see this and think that it would be easy for you to fix. maybe I'll feel better.

I'm hard on myself when I screw up and create rework. I do like learning new techniques though.

[JUDGE3]

to be clear, the areas don't pop-pop in and right back out by itself, and I would say thats the true definition of a can condition right?

the skin is warped/wavy below the tape area only and i can push it in and it stays and push it out from behind and it stays. occasionally it will pop in and back out.

the skin feels loose and weak.