First off, you HAVE to learn to use a hammer and dolly correctly to remove dents.No amount of wishing, or black magic 'shrinking' is going to do it for you. Shrinking sheet metal isn't easy, but it's necessary to learn when doing extensive metal work on steel. This includes dent removal, patch paneling, and customizing. Most welding could use some hammer work to get the sheet metal one step closer to perfection. Anyway, you can shrink metal cold, or hot. Cold shrinking is done in fabrication work, by using a 'soft' hammer, over a dolly, to 'compress' the metal into a smaller area. It can also be done with special machines, like shrinkers, or planishing hammers, or power hammers. There are also body hammers with 'waffled' faces that are supposed to shrink metal cold, by just hammering on it. Haven't had a lot of luck with them, though! Only in limited circumstances. Heat shrinking is the most popular application. First, be sure your metal is stretched, before shrinking! It may seem obvious, but sometimes it is not so easy to tell, and trying to shrink 'unstretched' or merely displaced metal will make a real mess! Simply put, when you heat metal, it expands. As it cools naturally (in room temp), it will shrink back down, but usually, not to the same shape as it was. It stays a little more expanded than it was originally. We put this to our advantage when shrinking metal. You heat up a spot, about the size of a dime, to a 'blue' color, or, as it used to be in the old days, to a dull red. The metal will rise up (expand) to a bump. Use a hammer, with a dolly back-up, and hit the bump down, almost flat. Leave a little to go, because as it cools further, it IS going to shrink a bit more, naturally. Gauging how much to leave it high comes with practice. The 'HIT' is important, you must do it right. I was always taught to hit the center with medium force, then work in a spiral outwards, with light force. I've seen others do it the opposite way with good results, too. In a badly damaged, or stretched area, you will have to do this over multiple times, in a large area, but not doing the same spot twice. Try to shrink along the line of the stretch, until you get it right. There is another way to do this, but unless you ahve a LOT of experience, it is less precise, harder to control. You can heat the spot, the same as above, but use a wet rag, or spray of water to quickly cool the metal, which shrinks it, also. But as I said, this method is harder to learn, and can do more damage than good if you mess up. It works more reliably, and controllably, on heavier guages of steel, than regular sheet metal, though. There is also concern that when you thermally shock the steel, it changes the temper of it, making it harder, more brittle, and it won't 'work' as easy. It can crack from regular hammer and dolly work, unless you anneal it (heat and let cool very slowly).
[ QUOTE ] i wanna learn how to remove dents with out hammers [/ QUOTE ] well, using a torch to heat shrink doenst guarentee you wont need hammers... the last time I used this method, I had to knock the dent OUT to where it was now a high spot, put a rosebud tip on the torch, then with a "cool" flame, heat the high spot, in a circular motion, til the center was a dull cherry red...tap the area with a hammer to knock it down a bit, then quench with a soaking wet rag from a bucket of water....had to repeat the process once, then it was just a matter of hammer and dolly work, then hit it with a file, and at last a skim coat of glazing putty... after sanding, primer, block sanding, and painting...you couldnt tell it was ever dented. I dont think there is a way to get out of using hammers when straightening a damaged [anel...but, then again, there are others here who know TONS more about this than I do...just thought I would post what little i know about the matter, in hopes that it helps you...
Make a 9 or 10" disk out of stainless steel, with a hole in the center so you can mount it on a large grinder(it needs to run at about 5000 rpm) Hold it on the high spots. It will heat only the areas it contacts. Cool with compressed air(I never cool with water) You'll think it's FM.
[ QUOTE ] Heat up the whole fender, and throw a bucket of water on it [/ QUOTE ] I thought that was a quarter panel. Heat shrinking was something we used to do on old cars (thick metal) after we hammered and dollied them and got too heavy handed. IE streched them out of proportion. Sometimes thats unavoidable. Basically we would heat up a spot about the size of a quarter and when it was starting to glow we would put a wet rag on it. Some guys say work from the outside in and others say work from the inside out. I usually worked from the outside in, and used less heat as I got closer to the center. Down side is that the metal has a tendency to get brittle and you run onto other problems later. Now a days I use a shrinking hammer. It looks like your standard body hammer with little points on the face. I think someone sells one that the head spins that's supposed to work real well. Don't be afraid to snag a hammer and dolly and learn to dolly one out. Start on the outer edge and work your way to the center of the dent. Take your time, and don't beat the hell out of it, you probably won't have to shrink anything. Note: there is no majic easy way to to body work. The old tried and true methods are the best.
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