Proper method for dent recovery

[Sixseven]

Years before I had the truck, someone dented the roof. It is the kind of dent you would get if someone sat on the roof which means a large part of the metal was dislocated rather than a small amount of metal as you would get for an impact from a branch. The result is a ridge along the rear portion of the roof.

What is the proper metal working method for removing this dent. I'm not interested in using a quart of this or that, but want to hammer it out.

[51 MERC-CT]

A picture would go along way to understand what you are talking about.
If as you say it looks like someone sat on it and then the center was popped out and left ridges on the outer areas this is a method I have used in the past.
Suction cup(s) to pull and keep pressure on low part while gently tapping (without denting) high ridge with hammer and tape covered steel paddle.
Recall doing one that did not even have to be painted.

[Barry-ct]

The metal has been stretched and now has to be heated and cooled to shrink it back to it's original shape. They usually heat up a small area and then cool it quickly with a rag soaked in water. It's a time consuming process and a experienced bodyman would know how and where to start.

[34PKUP]

Originally Posted by Barry-ct

The metal has been stretched and now has to be heated and cooled to shrink it back to it's original shape. They usually heat up a small area and then cool it quickly with a rag soaked in water. It's a time consuming process and a experienced bodyman would know how and where to start.

The metal has been stretched and has to be shrunk?
An experienced bodyman would not make that determination without seeing the damage or picture.

[G.M.]

The metal may or may not be stretched. I would get two guys inside and put the back of your shoulders up against the roof and push it up. Most of it should pop back up.
It may be a little wrinkly around the edges which will have to be straightened.
I would avoid heat on a large metal panel as it can warp. G.M.

[flatheadmurre]

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A roof thats not perfectly flat is a nice piece to straighten.
Think like you want to rewerse the damage so if dent started in the middle going out to edges you start pushing out the dent from the edges working your way in.
Pressure and soft pads until you get it out then start with the shrinking/flattening needed.
It usually gets surprisingly good when you pushed it out.

[Scott H in Wheaton]

Take a wire coat hanger and bend it in the mddle, then try to straighten the bend and make it look like original. Chances are you can't do it because the bend stretched and realigned the grain of the metal.
Same thing happened to the roof dent.
Concentrated heat will relax the metal and allow re-shaping it.

I agree with working the dent backwards. Point of impact will be the center of the dent and since its the first oart to get damaged it shoukd be the last part to push back. Work it slowly from the edges.

[Kube]

I have rarely been able to repair a roof that has been damaged in the way you describe without shrinking the metal. It is not an easy task to do properly, regardless of experience doing these types of repairs. It is a tedious process but one worth the efforts if, like me, you prefer not to fill with an ominous amount of putty.
It is pretty much "body work 101" to pound out a dent as Scott has described in post #7. I'd take his advice to heart.
My advice? Get the dent as close to "out" as possible (again, refer to post #7) and then, where necessary, shrink the metal. A high quality shrinking hammer is a great aid in this process. Simply heating the metal and throwing cold water on it, well, that helps - a little. Heating, utilizing the shrinking hammer and then dousing with cold water works much better.
Do not expect this repair to come easily and quickly. It will require patience.

[flatheadmurre]

Since the roof is curved in two axis its not needed to get it 100% free from stress in the metal so its a fairly nice job.
A flat smooth side of a car thats gonna be gloss black .

[51 MERC-CT]

Originally Posted by flatheadmurre

Since the roof is curved in two axis its not needed to get it 100% free from stress in the metal so its a fairly nice job.
A flat smooth side of a car thats gonna be gloss black .

'51 Merc. skirts used to be curved in two axis (bellied ) not any more after a lot of heat shrinking.

[flatheadmurre]

Nice gaps and mirror finish
Thats real eyecandy !

[KiWinUS]

That is "craftsmanship!" 51M.....great fit !!!!

[rotorwrench]

Shrinking and stretching of large panels takes some skills that are developed with time and experience. You don't always need to quench a cherry red shrink with water. Sometimes you don't even need to heat it to a red color to get a good shrink. I've used a shrinking disk mounted on a body grinder spindle and they work pretty well but like anything new to you, it helps if you can get instruction from someone with experience. I frequent the metal meet web-site and there are some pretty knowledgeable folks on there. I also have a CD that was made by an experienced metal shaper and it is full of all sorts of tricks of the trade.

A photo is worth a thousand words when you are dealing with wrinkled metal. Especially if it is on a roof.

[deuce_roadster]

Having done many heat shrinks with a torch and air, there is a better method.
After first working the metal best as you can using a SPOON, someone mentioned above, use one of the new stainless steel shrinking disks. These go on a 4 or 6" grinder. The beauty of these things is the disk uses friction to heat the metal to a temp that will shrink and best of all, it will ride on the HIGH spot or RIDGE left by the dent leaving the low part untouched and only heating the part you want to shrink. Then use your air to cool it. Yeah you can use water but air works just fine. If you have never used one of these give it a try. The other thing you can do is because the disk is rotating you can slightly influence the metal to move via the circular motion in a direction that is advantageous to you. It is pretty amazing. I was skeptical at first but those things work pretty slick.
I prefer to not use the shrinking hammer as that method is just making small indentations to shrink the metal which works on large flat spots but when you are working the slight ridges like big roof dents make they are not so effective.

[alan]

did a roof on a 40 pick up last summer. removed the seat, took a jack and a 4x4 , a block of wood fitted to the concave of the roof. put tension up on the roof, used a hammer and a dolly on the creased area, sometimes in creasing the pressure with the jack. when I was thru, used less than a golf ball size blob of filler to finish it off before coating with a layer of heavy build primer. roof came out great. the roof on my 41 truck looked like a persn had danced on the roof, it also looks great

[Sixseven]

Difficult to photograph. The roof is not caved in, it apparently flexed inward enough to create a ridge at the rear of the roof. In the photo, the dent appears as a depression. It may be that some depression is present toward the front of the truck roof, but a ridge is what my palm feels. Thanks for the input folks.

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[IMG][/IMG]

[rotorwrench]

You definitely have a king size butt print there. A person doesn't want to push the low spots up too high but they will likely have to be pushed up as far as practicable before starting the work those ridges down. This will require a person to work it in stages. A person can use the torch to shrink it a little bit but the slapper, spoons, & maybe a bit of dolly work might still be some use prior to or during shrinking. A shrinking disc would be a good tool for a lot of the shrinking needed there. If there is structure underneath that, it can complicate the use of slapping & dolly work. If so, the structure would likely need a bit of working too to help support the changes that need to happen there. Good body files will finish the metals back to smooth after it's worked as close as you can get. There are a lot of simple tools that can be made in your home shop that will help do the required work. You can buy them if you are so inclined but most guys make what they need to do the job at hand until they have a good general collection of stuff.

Check out the metal meet forum and don't hesitate to post questions there. U-tube has a lot of info on it if you can find something similar to the problem you have there. What you have there can be reformed back to original contour but it will take as much knowledge you can find before making the attempt. I would look for the easiest ways to complete that task. It is easy to chase your tail on a spot like that if it doesn't reshape as you want it to.

You can fabricate contour gages from heavy card board or lauan off the other side and make a grid for checking the contours in the affected locations in order to get the right & left sides to match up close again. Some folks just do it by eye but not every one has the same eye for it.

[Marvin/TN]

Nope, don't heat it and don't cool it. As far as experience goes is 44 years in the collision business enough?? Just push up on the low area and with light glancing blows from a body hammer toward the center of the low part. Don't try to do it all at once just slow and easy does it. A roof will have high enough crown that the stretched part should be easy to move.

[Sixseven]

Thanks for the reference to Metal Meet forum. I'll see what they are all about.

Marvin/TN: Do you not suspect the low spot has stretched the metal around the dent?

[FlatheadTed]

Get a porter power and fix a low crown dolly to it ,lightly jack inside on the low spots .Put a bit of tension on and then hit the high spot next to the dolly on the out side .Use a wide face body hammer or slapper iron ,don't use heat at this stage ,Ted