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Old 10-22-2005, 07:25 PM
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Panel warpage help?

Auto body newb here:

I just finished welding in new cab corners on my truck. I was dumb and welded it in without trimming around the depressed area on the rear cab wall. Instead I welded the small projection into the depressed area figuring I could dolly out any warpage that happened. It looks good, but now it is stressed to the point that the area within the depressed "box" pops inward or outward. I tried the hammer / dolly thing, but only the welded area flattened out. How do I stress relieve this area?

Thanks in advance

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Old 10-22-2005, 09:04 PM
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You have what sounds like an "oilcan". I've been taught to break out the oxy-acetylene torch to eliminate this condition. I'd bet MARTINSR has a tutorial all about it, it seems like it would be hard to put into writing what you need to do, though. Basically, you heat up dime sized spots red hot with the torch in the areas that are most stetched. Immediately after heating, you hammer and dolly the heated area down flat, not hitting too hard, and quench the area with a wet rag. An important tool to have for this procedure is a stand that will hold your lit torch or a helper to hand it off to while you hammer. Speed is of the essence! I'm leaving a lot out that I'll leave to others to fill in...
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Old 10-23-2005, 08:20 AM
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It sounds like you may have overlapped the panel? If so, you will have a difficult time getting it straight. Do you have any pictures of the panel? If you could show where it is popping in and out, that would be great. You most likely need to do more hammer and dolly work before any shrinking.

For heat shrinking with a torch I suggest heating only to a blue heat...actually only until the metal steams when quenched. Try a practice panel first. If you heat to red, the metal will be more difficult to work.

A better method of shrinking and smoothing a panel is to use a shrinking disc. Here are two albums and an article that might be of help:

http://allshops.org/cgi-bin/communit...=9980121727059

http://allshops.org/cgi-bin/communit...=9980124046566

http://metalshapers.org/101/jkelly/index.html

The article has some hammer and dolly tips as well as shrinking disc use, but may help you even if you use a torch for shrinking.

John www.ghiaspecialties.com
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Old 10-23-2005, 08:13 PM
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Thanks guys. For the torch heating; should I work the weld seam only? I went at it with a body hammer and dollies and got it about half way to where it should be....(no heat) I butt weld the seams, but the weld area sucked in to form a groove of sorts. The circled area represents the oil can dent that pops one way or another. After the pick and dolly work, the area directly next to the cab corner flattened out, but not the oil can above... (Pay no attention to the orange marker....just my way of reminding me of areas to fix)

I know the box will cover this area, I figured this was an excellent learning opportunity....Besides, who knows who will look in there?

My idea of saving this truck and learning how to do all this stuff the hard way? DUMB & never again......next project? = southern & complete..... oh well.

Thanks in advance

Gear
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Old 10-23-2005, 09:46 PM
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The original sheetmetal in the area circled should be just fine. It is just under some stress from the shrinkage that took place at your welded seams. If you hammer and dolly the weld seams within the dished area it should stretch the shrunk area back out which will then let the sucked in stressed area relax to it's normal position. Use a hammer on dolly technique on the weld area. If you try and shrink that sucked in area it probably won't help other than to make is a little mellower and maybe larger. Bob
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Old 10-24-2005, 06:50 AM
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In additions to Bob's good advice, do not shrink before getting the metal smooth, and even then, only where the panel is obviously high or has too much surface area to fit where it used to. Usually the need for shrinking is caused by the hammer on dolly work having stretched the area slightly.

Another consideration...sometimes you will miss a small dent outside the oilcan area that should be fixed before addressing the oil can. And, sometimes you need to bump the metal out a little with a dolly and then go back to hammer on dolly work.

Since that is a recessed area, you might try using a small flat machinists ruler laid against the surface to help locate highs and lows that need to be worked before shrinking.

If you can, hammer from the inside directly on the weld seam with a flat dolly on the outside to flatten out the valley before any of the other work.

Nice looking repair job!

John www.ghiaspecialties.com
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Old 10-24-2005, 06:52 PM
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Thanks again for the tips guys, and the kind words John.

I will try to concentrate on the weld seam a little more carefully. I have yet to buy a torch (I still don't have one believe it or not.....I just brought it home from the shop where I work) so I'll have to try it cold for now. I was jumping around too much I think. I'm also having difficulty swinging the hammer in such a tight area. (Inside the rear pillar channel)

I lightly sprayed on some flat black so I could sand it off and find the highs/lows. What A fright I got when it flowed on! Ugly stuff. wow. Sure identified the trouble spots though.

Cheers fellas.

Last edited by Gearhead forever; 10-29-2005 at 09:04 AM.
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Old 10-24-2005, 10:00 PM
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“Basics of Basics” overview of shrinking
By Brian Martin

Where is the dent and how big is it? These may be deciding factors in how you repair.

If your panel needs is shrinking. You can do this in many different ways, again depending on where and what size the dent is.

You could use:

A torch. This can provide the most heat for shrinking, consequently the most DAMAGE. Do not heat til red, light blue is fine.

A shrinker attachment on a spot or MIG welder. This is a great way to shrink small dents or thin metals.

A grinder. Yes, with an 80 or 100 grit disc and a lot of speed you can heat the high spot and cool it to shrink, without taking "much" metal off.

A grinder with a “Shrinking disc” . This is an amazing tool that does exactly as advertised. It is basically a “Heat block” heating only the high spots.

A "DA". With it in the "grinder" mode and some 120 grit, use it the same as the grinder. I do this all the time, it is very useful.

A Heat gun. There are electric hand held heat guns that provide you with 1000 to 1500 degrees of heat.

Simply use an “off dolly” technique with a hammer and dolly. Push up on the panel with the dolly, then tap around the area OFF the dolly. Many times there will be high spots anyway around a low spot so this works perfect. Remember, do not hit the hammer where the dolly is. That is called “on dolly” and STRETCHES the metal.

There are different methods for shrinking, you heat and cool or you heat and work.

Heat and cool is usually for areas that you can't get behind, very small low spots, or very thin metal. This is the easiest way in that you just apply heat and then cool with air or water and the area will be shrunk. Cooling with air really works well.

I have done some little tests and blowing the heated area with a blower on your air hose shrinks almost as much as quenching it with water, without the rusting concerns. When the metal cools the molecules get closer together in the heated area, thus pulling in on the surrounding area
and shrinking the surface area of the panel.

Heat and work is a bit trickier. You heat (usually with the torch) and put a dolly behind the heated metal and gently strike the heated area with a hammer “On Dolly” (the largest, flattest hammer you have). When the metal is hot the molecules are free to move about. So after heating and before the metal cools, tapping on the heated area (that has either raised
or dropped) allows you to “push” them to where you want them.

You have to do this carefully, because if you hit “On Dolly” too hard, you will push those molecules apart, and make matters worse! The idea is to gently push the molecules to the center of the heated area and this will “pull” in on the surrounding metal. Picture a 12 x 12 inch 1/4” thick tile of playdough. If you maintain the 12 x 12 but thin the Playdough
down to 1/8” you would have a big hump in the middle right? Well this is what the metal is doing, you have to move the molecules like the particles of playdough back to the proper place. When you heat that sheet metal, believe me you don’t have to hit it much harder than if you were hitting Playdough, so be CAREFUL!

Precautions:

Bare metal is the best to shrink, especially the back side. BE CAREFUL THAT THERE IS NO UNDERSEAL TO BURN, and besides if you are going to “work” it cool, thedolly gets all covered with underseal.

Get a partner to hold the torch while you “work” the metal. And this partner can also keep a fire watch.

Make sure you know what is behind the metal you are about to heat, wires, lines (like FUEL!) should be removed. And that sound deadening material can be VERY flammable (I know all to well about that one!) .

The metal will only do what you tell it to do. It has a memory and you have to “help it to remember”.
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Old 12-03-2005, 05:02 PM
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I finally got myself an oxy-acet torch. I played with it briefly and got things to straighten out quite a bit. I still have a lot of finesse work to learn though. It seems I can get it so far and thats it. I will keep plugging away to get it just right. I could slap on some filler and be done with it, but thats not the point. Thanks again guys!
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