Auto Badi question - oil canning

[MGKelly]

Hello, I have a question and hope someone can help..
I had a small but deep dent on my RR hood and hammer it out, then used some heat to shrink the metal to get the oil canning out. used a propane torch, just waited till the metal got blue not red, then lightly hammered and then cooled. the dent and hood were coming out real nice. there was a small area that was a little high and hit it with the propane torch again and what happened then was part of the hood in area i was working concaved. "metal flexed the opposite way and stayed there". I can still flex it out by pushing it, but it immediately flexes back.

So my question is, do i need some additional shrinking or did i shrink it too much? I'm not going to work on it again until I fiqure out what happened.

Thanks, Joe

 

[MGKelly]

Auto Body - Not Auto Badi = I can write English i think

 

[slimt]

I dont think propane is hot enough to get the dime size yellow burn you need. You can get a attatchment. Two lines feed to one torch tip with a oxygen tank. And propane together. Heat the area required from the outside in to a dime size yellow red hot. Find a metal spoon poke inside the hood area and tap the outside around the burn then cool with a rag with cold water. only heat the area that requires the shrink..It will tighten up. You can only do this so many times before warping takes place. The propane with air is a option to make it work. The air in tank will not last long.

 

[slimt]

A picture of what your doing would be great. And the area you are working on.

 

[MGKelly]

first picture is of the bottom of the hood, the like running horizontally was the dented area, dark areas are the torch marks. hit it with the torch 4 times across the dent after tapping most of the dent out.

Second picture is the top were i last applied heat that caused the hood to oil can. red where i applied heat and green circle is the area affected (the metal is now flexed the opposite way - it's a bulge hood)

 

[slimt]

first picture is of the bottom of the hood, the like running horizontally was the dented area, dark areas are the torch marks. hit it with the torch 4 times across the dent after tapping most of the dent out.
View attachment 500774
Second picture is the top were i last applied heat that caused the hood to oil can. red where i applied heat and green circle is the area affected (the metal is now flexed the opposite way - it's a bulge hood)
View attachment 500775

okay.. how much of a bulge? is there a brace behind that area? to shrink.. you need cold water.. heat , tap and dolly around the deepest area, then cool with water.. soon.. it will tighten up.. when shrinking.. you only need to do the effected area.. not all of it.. remember.. you need oxygen with propane to get it hot enough to get the dime size red yellow then tap then cool.. that area should only take one time..

 

[MGKelly]

It flexed in about 1/8 of an inch measuring from the center of the green circle. where should i apply the heat? Center of the green circle?

thanks Joe!!!!

okay.. how much of a bulge? is there a brace behind that area? to shrink.. you need cold water.. heat , tap and dolly around the deepest area, then cool with water.. soon.. it will tighten up.. when shrinking.. you only need to do the effected area.. not all of it.. remember.. you need oxygen with propane to get it hot enough to get the dime size red yellow then tap then cool.. that area should only take one time..

 

[Photon440]

If you have no oxy torch, you can get by with a mapp gas or high intensity propane torch by using a shield. Cut a 3/4" hole (or whatever size is appropriate for your project) in a scrap piece of metal and place it over your dent so you can heat it up without letting too much heat get everywhere else. It won't take long to glow, then you can quickly tap and quench it to shrink.

Also very effective, but costs a bit more is thermal paste that you can spread around your work area and just leave exposed what you want to have heated up. http://www.eastwood.com/coldshield-thermal-paste.html

 

[slimt]

It flexed in about 1/8 of an inch measuring from the center of the green circle. where should i apply the heat? Center of the green circle?

thanks Joe!!!!

do you have access to the back of that area?
photons onto something as well..

 

[MGKelly]

Yes i have complete access to the back!

 

[slimt]

Yes i have complete access to the back!

the dent has to be in.. heat it up.. see it rise.. then dolly on the back and tap the top down lightly around the dime burn.. then cool right away.. to keep the heat from spreading causing it to warp.. soak paper towel and create a ring around the area with the towel. this should tighten up the canning..

dont shrink to many spots.. it will go the other direction which you dont want..

 

[MGKelly]

You're saying that I need some additional shrinking to the area that had the dent?

 

[slimt]

if you said its oil canny.. yes.. all panels flex..

 

[1967coronet]

Just my 2cents , but each time you move that steel its growing in size. A road runner bulge hood is not the place to practice shrinking a spot on a panel.
Get a old fender or door skin and smack a couple similar dings in it and play with your heat and cold / wet rag to get a feel for it.
.
You can also use a shrinking disc but again practice on a junk panel.