I had a bad bit of Oil Canning in the center of my tailgate, it would spring into a concave shape, you could press the center and it would pop out, but as soon as you let go it would spring back again. I did a bit of reading on the best way to try and resolve the problem and came to the conclusion that the best way would be to heat shrink the metal i.e. Heat a small area in the center of the oil can and let the cooling metal then pull the stretch out.

I was cleaning up the tailgate getting ready to take on the task when Roger (Old Guy I rent the corner of my garage from) came by asking what I was doing. I explained what I was about to do and he winked at me and then proceeded to tell me how I SHOULD do it. He told me to find a lot of old newspaper and make myself some paper mache. Then make a dougnout out of it around the area I was heating, effectively making a heat shield for the rest of the tailgate. This ensures that all of the metal around the heated area remains cool and the heated metal has nowhere to expand other than in its thickness.

It was a very simple thing and fairly obvious, but I never thought of it.


After cooling the tailgate is as taught as the day it was stamped . All I had to do was a little plannishing. Needless to say, I am well chuffed with the outcome.


I have seen a number of threads on shrinking, so wanted to share this very simple but effective tip.

Hope it helps someone else out as it did me.

Lee

 

Thanks for the tip Lee. Never thought about that but it makes sense.

 

Lee,

We all have trouble with "Oil canning" when we hammer out dents. Thanks for the newspaper tip. I have successfully shrunk a lot of metal be never thought of using wet newspaper to concentrate the heat, very simple,and cheap, way of doing it. I sure it will come in very handy in the future.

Thanks

 

Lee,

Wow, what a simple adn creative idea for a heat shrink. Thanks for passing that on to us.

Aren't those old timers amazing? If us young and dumb guys would just listen its amazing what we can learn.

Bobby

 

What a great tip !!! I'v also seen where they'll use play dough or silly putty a few inches above a weld to act as a heat sheild.

 

Excellent tip!

Be sure to tell the old-timer that he blew the socks off a bunch of Colonials.

 

Thanks Guys,

I will be sure to tell Roger his tip was very well received. He is full of old tips and tricks and a lot of knowledge about trucks too. He is a nice old sort, but suffered a bad stoke a few years ago and struggles to talk and has lost most of his co-ordination. I can see his frustration in his eyes a lot of the time, when his mind is still as sharp as it ever was, but his body just lets him down.

Lee

 

A few tool places sell expensive "heat absorbing" compounds to do exactly the same job.......except they stick to vertical surfaces

I have used wet towels or play dough before, but the paper mash idea is great.

Added to the mental fileing cabinet.

 

Lee

Thanks to You and Roger.
I really enjoy finding someone like your Roger to talk with and get their expierences about many different subjecst. Newer isn't always better.

 

Your post interests me alot because I have a similar problem. I butt welded a patch on the rear quarter panel of my panel truck, and on the seam of the weld I've got a hump that I can't seem to beat flat. I suspect that the metal has expanded, I've tryed heating it and hammering it but still with no success, it does not how ever have an oil can effect it's just a bump a little larger than a golf ball. I know that I must be doing something wrong but don't know what. I've also tried heating it and applying a wet cold rag. It has me stumped and have left it alone fearing that I would do more damage, if it were sunk in I would just fill it in with bondo but as you've guessed it sticks out like a sore thumb, about 3/16ths of an inch. Will this method you have discribed work for me? Hoping so.John

 

This might make for a great post in the bodywork forum.

Thanks for the tip. I can sympathize with his frustration. I shake so bad it is hard for me to even hold a wrench and tighten a bolt.

I have used a rag soaked with motor oil and a torch to heat/cool and shrink metal also. Makes for a lot of smoke but the oil keeps the metal from rusting.

 

Hard to diagnose without running my hand over it, but it sounds like there is just too much metal there. If heat shrinking and on/off dolly slapping won't bring it down you may need to slice the weld with a 1mm disk and then reweld it.

What is the original weld?.......I am guessing it is mig, which would explain the inability to shrink across it.

I would slice it, then hammer weld it with a henrob (oxy) tourch at a nice low heat, with plenty of massaging as you go.


........or lay the panel on it's side and put paper mash around it ........

 

Thanks for replying so quickly, I did use a mig welder as you guessed. I will try slicing and rewelding as you suggested.Thanks again John.

 

Excellent tip, thanks for sharing it.

 

I once had to cut some holes in a stainless plate with a hole saw and was having a hell of a time. An old electrician told me to fill the holesaw basket with window glazing putty. It worked like a charm kepping the basket cool so it wouldn't bind in the hole. I've found that more experienced tradesmen always have some tricks up their sleeve.