I allways seem to run into streched metal on the easyiest looking dents.
They allways turn into a pain in the A-- and I wind up working on the same place for two days before I finally get out the torch and start shrinking.
Or at least thats what I call what I do to get it the way I want it?
Can you give any pointers or advice on this subject and metal bumping in general?
thanks T.C.

It seems that there are 2 ways to shrink metal that is in the middle of a panel that is still attached to a car. One is the torch method where you clean the metal, check for flamables, heat an area the size of a dime to red hot, hammer the area back down into itself. If additional shrinking is required, quenching with a wet rag will help.

The second way that I know is by using a product from Sunchaser Tools (626) 795-1588 called the incredible shrinking disk. The disk is made out of Stainless Steel. It is about 9" in diameter and has serations along its edge. You attach the disk to a 6000 RPM grinder and apply it to the area that needs shrinking. The disk will only hit the high spots, turning them blue. Take the disk away and quench the area with water and repeat as needed.

As for tips on metal bumping, etc., the most important thing is to try to avoid creating a streached area when doing the repair. Stretching metal is easy, shrinking is much harder.

It would be impossible to give a complete expaination of the process of metal bumping or sheet metal work in a post like this, so I will offer you a couple of resources to look into on your own. If you are really serious about doing quality, low (or no) filler body work, then these sources are a good place to start.

Yahoo groups has a couple of groups setup called metalshapers and autobodyrestoration. They were started by this guy named Terry Cowan. Terry wrote the book literally on auto body solder. Join the groups (free) and ask any question you wish. Look through the archives and you will find a vast wealth in info related to metal work. There is also a website www.metalshapers.org (http://www.metalshapers.org) that has quite a bit of info.

As far as books to get you started (or going back in the right direction), Eastwood sells a book by Frank Sargent called the Key to Metal Bumping. It is a small, book that has a decent amount of at least good intro info to improve just about anyone's body work.

Hope this helps.

David Selko

David, great stuff. I have a "Shrinking disc" and it IS amazing. I describe it as a "heat block" heating only the high spots. I have metal finished late model Japanese panels, one time a Toyota where the metal was literally folded over it's self! It really is a neat tool, but be sure you get the (Ken at Sunchaser has the lowest price I could find) the 15 amp 5000 RPM grinder, you really do need it.

T.C., if you need more here is what I have. It is sort of a short "basics" but there is something there that will shed some light I hope.
>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>> 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.

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 "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” think 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, the
dolly 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"


------------------
1965 Buick Gran Sport Convertible
1965 Buick Skylark H/T
"Fan of most anything that moves human beings"

Thank you David and MARTINSR:
I learned alot in just your two post.
I have the little red book and have gotten alot of good info. from it.
I also see by your post I have been doing some things wrong, but my body banging is now coming to an end on this car and those spots arent really bad enough to redo.
Mabe if you guys have the time you could continue your mini lessons and post a little at a time for us beginers?
There is nothing like first hand info. and the small tricks that arent in the books.
thanks T.C.