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Unread 09-20-2010, 09:46 PM   #1
Bigbob
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Shrinking Metal

I am building a trailer and I used 18 ga cold roll on the tailgate. I have it all tacked in and don't need anymore welding done to it. I have some warpage. Not bad, but I want to straighten it as much as I can. So, to lower the high spots can I heat it and quench it with a wet rag to shrink it? Any advice would be appreciated.

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Unread 09-20-2010, 09:48 PM   #2
g4x4xgeoff
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go out and grab some "auto body shapers and hammers"

using them together will shrink, and some expand steel where necessary.
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Unread 09-20-2010, 10:10 PM   #3
dodger889
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Unless you have a rosebud tip on a gas torch you would be fight a losing battle. Heating the high part of the bubble or wrapped part. Then quick cool the the back side will draw it some not alot but some would come out. This is why you tack and move (couple of inches), tack and move untill you get all the way around till you have it welded in.
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Unread 09-20-2010, 10:40 PM   #4
Bigbob
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Originally Posted by dodger889 View Post
Unless you have a rosebud tip on a gas torch you would be fight a losing battle. Heating the high part of the bubble or wrapped part. Then quick cool the the back side will draw it some not alot but some would come out. This is why you tack and move (couple of inches), tack and move untill you get all the way around till you have it welded in.
No continuous welds. It's all tacked in about every 2-3 inches or so. Around the perimeter it's welded continuously, but I tacked it all first then just kept tacking around till it was complete. It's in the center between the supports I have an issue.

I'll try a mapp torch and wet rag before I do the rosebud. This is slight warpage and I think the rosebud is gonna put down too much heat on that 18 ga.
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Unread 09-21-2010, 12:39 AM   #5
Netpackrat
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Getting oil can out of the middle of a flat panel is tough. I've seen it done with a power hammer, but those aren't exactly common, and quite expensive. Might almost be easier to turn your oil can into an actual dent, and shrink it down using a wide headed body hammer, and a big shot bag. I think you will find the results from using ANY torch and quench method less than satisfactory.
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Unread 09-21-2010, 06:58 AM   #6
Bigbob
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Quote:
Originally Posted by Netpackrat View Post
Getting oil can out of the middle of a flat panel is tough. I've seen it done with a power hammer, but those aren't exactly common, and quite expensive. Might almost be easier to turn your oil can into an actual dent, and shrink it down using a wide headed body hammer, and a big shot bag. I think you will find the results from using ANY torch and quench method less than satisfactory.
Oil can?
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Unread 09-21-2010, 11:09 AM   #7
TJ06WRANGLER
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There are some outfits that make a shrinking disc. Can't remember the names off the top. It goes on your disc grinder and apparently works very well.
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Unread 09-21-2010, 11:35 AM   #8
jpony645
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There is also a "shrinking" hammer. Basically just like the other body hammers but with a waffle face. Use it along with a dolly to pull the metal in and flatten it out.
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Unread 09-21-2010, 12:09 PM   #9
Bigbob
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Originally Posted by TJ06WRANGLER View Post
There are some outfits that make a shrinking disc. Can't remember the names of the top. It goes on your disc grinder and apparently works very well.
I've seen those. I've never used one. I've done the heat and quench deal before but never on something this minor. I may try to see if I can find a disc.
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Mods done: Hurst tee handle, cheap hand throttle, Rokmen Merc front bumper, Warn 9.5 TI winch with 3/8" X 100 worth of Viking yellow rope, DPG OME Ultimate with JKS ACOS up front, Kilby Gas Tank Skid, Kilby Steering Box Skid, Jeep Medic Belly Up, Skidrow Engine Skid, Rockcrusher Diff Skid in the rear, Warn Diff cover in front, , AR Outlaw II's and MTR 12:50/15's, Homemade rear Bumper, Cheap Cobra CB, Puma OBA, Sirius Radio, Locker Defeat, Rockhard cage, Rockmen short corners, homemade tire swing/tailgate hinge affair, Airlift air bags on the rear- - - - - - and more to come!
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Unread 09-21-2010, 12:12 PM   #10
BigBass
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depending on what kind of torch you have you might not need to buy a rose bud, though there good to have, a #3 or 4 cutting tip will put plenty of heat in there turn that 18g in to puddle. The shrinking hammers might be your best bet though.
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Unread 09-21-2010, 02:08 PM   #11
Bigbob
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Quote:
Originally Posted by BigBass View Post
depending on what kind of torch you have you might not need to buy a rose bud, though there good to have, a #3 or 4 cutting tip will put plenty of heat in there turn that 18g in to puddle. The shrinking hammers might be your best bet though.
LOL. It is 18 gauge. It don't take much heat to get it to stretch or shrink. I sure ain't looking for any "Cherry Red" action here.
I am ordering a Wolfe 4.5" shrinking disc. Looks like a cool toy. I'd rather have the larger size, but I don't have a large grinder. You can search "Shrinking Disc" on you tube and see some cool how to videos. I think they have videos on the Wolfe site as well.
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Unread 09-21-2010, 06:24 PM   #12
Netpackrat
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Quote:
Originally Posted by Bigbob View Post
Oil can?
When you have a stretch in the middle of a panel, so that when pushed it will flex and snap like an old style oil can.

Quote:
Originally Posted by jpony645
There is also a "shrinking" hammer. Basically just like the other body hammers but with a waffle face. Use it along with a dolly to pull the metal in and flatten it out.
The meat tenderizer hammers, and the so-called "shrinking" dollies with a similar surface are just a gimmick and won't shrink anything; about all you can count on them to do is chew up the surface of your metal. Best thing to do with one of those hammers is to grind and polish it flat into a regular hammer.
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Unread 09-21-2010, 06:38 PM   #13
Bigbob
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Quote:
Originally Posted by Netpackrat View Post
When you have a stretch in the middle of a panel, so that when pushed it will flex and snap like an old style oil can.

Thanks, I figured that out watching video on the shrinking wheel. Very good descriptor phrase.

Quote:
Originally Posted by Netpackrat View Post
The meat tenderizer hammers, and the so-called "shrinking" dollies with a similar surface are just a gimmick and won't shrink anything; about all you can count on them to do is chew up the surface of your metal. Best thing to do with one of those hammers is to grind and polish it flat into a regular hammer.
Ditto. I don't see how you can shrink something by hitting it? I can hit this wave, which is basically a "oil can" deal, all I want and it may pop the other direction, but the metal has to be shrunk to get it out. Small dents can be dollyed and tapped close. This is a 4-5 inch area that will just spring from one side to the other. If measured, I'd say it sticks up maybe .050 or less. In bare metal form you can't see it. You can feel it and it'll stand out like a sore thumb once painted. I will need some filler on this panel and a couple other places. But all I want to fill is pinholes and imperfections from welding.
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Mods done: Hurst tee handle, cheap hand throttle, Rokmen Merc front bumper, Warn 9.5 TI winch with 3/8" X 100 worth of Viking yellow rope, DPG OME Ultimate with JKS ACOS up front, Kilby Gas Tank Skid, Kilby Steering Box Skid, Jeep Medic Belly Up, Skidrow Engine Skid, Rockcrusher Diff Skid in the rear, Warn Diff cover in front, , AR Outlaw II's and MTR 12:50/15's, Homemade rear Bumper, Cheap Cobra CB, Puma OBA, Sirius Radio, Locker Defeat, Rockhard cage, Rockmen short corners, homemade tire swing/tailgate hinge affair, Airlift air bags on the rear- - - - - - and more to come!
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Unread 09-21-2010, 11:44 PM   #14
Netpackrat
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Quote:
Originally Posted by Bigbob View Post
Ditto. I don't see how you can shrink something by hitting it? I can hit this wave, which is basically a "oil can" deal, all I want and it may pop the other direction, but the metal has to be shrunk to get it out. Small dents can be dollyed and tapped close. This is a 4-5 inch area that will just spring from one side to the other. If measured, I'd say it sticks up maybe .050 or less. In bare metal form you can't see it. You can feel it and it'll stand out like a sore thumb once painted. I will need some filler on this panel and a couple other places. But all I want to fill is pinholes and imperfections from welding.
These links probably won't be a great deal of help with your specific problem, but they do show somebody shrinking metal just by hitting it with smooth faced tools:

YouTube - Shrinking Metal with a Plastic Mallet

YouTube - Air Power Hammer - Shrinking Steel (14-gauge, hot-rolled)

Bottom line, large, flat spans of thin sheet are hard to keep from distorting, and even harder to return to flat.
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Unread 09-23-2010, 04:11 PM   #15
Jason_alex
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18 GA. Is thin enough, heat the back side of the low spot and just let the air cool it it will expand at first but then pull back down farther than before.
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