Sheet Metal Shrinking:

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Has anybody seen a shrinking head for a welder lately? I had one years ago but it seeminly grew legs and walked away. I usually use a torch for this operation but would like to purchase another head if still made.Thanks,SlobPurveyor of intimate unparalleled knowledge of nothing about everything.Oh yeah, also an unabashed internet "Troll" too.....
Reply:Originally Posted by SlobHas anybody seen a shrinking head for a welder lately? I had one years ago but it seeminly grew legs and walked away. I usually use a torch for this operation but would like to purchase another head if still made.Thanks,
Reply:Originally Posted by Ian Duffin...what is that?Sounds like a pipe stretcher
Reply:Originally Posted by SlobIt is actually a real tool that gets really hot, (white if you let it) in a concentrated spot when held against any conductive surface using the welder as a power source. Sort of like a carbon arc torch but no consumables involved. It will make a hot spot about the size of a silver dollar and when the head is pulled from the conductive surface and a cold water soaked rag placed upon the spot immediately, the spot rapidly collapses or shrinks. It's how you get what is called "oil canning" from sheet metal panels and is an art in itself. This used to be common practice in the auto body industry when people actually repair cars rather than simply replace parts.
Reply:Originally Posted by Ian DuffinNo kidding, ill have to check that out, sounds neat!
Reply:Slob, I had a MIG (Century) for a while that came with a shrinking tip.  Basically it was a carbon rod threaded to replace the contact tip. To use it I could pull the wire back into the liner, turn off the feeder and set the heat on KILL.  Press the tip against clean metal and squeeze the trigger until it looked about right, release trigger and finish the shrink.  I was taught to hammer around the hot spot and raise a "bubble" in the center.  As with anything in sheet metal hammering, there is more than one way to "skin A Door".  I learned from old timers that thought lead was cheating and that any body man worth his salt should be able to "hammer, dolly, shrink, and file".FWIW I have also used a pin spotter for the dent puller pins as a shrinking spotter.  Kind of small spots but good control.  I just replace the pin with a length of heavy gauge solid copper wire.RogerOld, Tired, and GRUMPYSalesman will call, Batteries not included, Assembly is required, and FREE ADVICE IS WORTH EXACTLY WHAT YOU PAY FOR IT!Dial Arc 250HFThunderbolt 225 AC/DCAssorted A/O torches
Reply:I have a shrinking tip for my pin welder which works well for small shrinks but it is slow to use except for finish type work. Know what you mean about lead and finish work; It's how I was raised in the 60's to early 70's when starting out. Lot's of talent lost through the ages for certain.I have an antique truck which was sitting in the barn and wind loading made a couple of bales fall from the overhead storage area onto the front sheet metal of the truck's hood and fenders. The sheet metal can be straightened but I don't like plastic filler on such a high vibration environment, (diesel engine  dump truck) unless it can't be helped. I figure I'll rough back into shape, shrink the stretched metal buckle back to close original contour using a torch, cross pick, and needle, then polyester prime so if any filler is used, it will be very slight.SlobPurveyor of intimate unparalleled knowledge of nothing about everything.Oh yeah, also an unabashed internet "Troll" too.....
Reply:Roger you are correct. The center of the "shrink" will glow a cherry red to almost white and just as you remove the source of heat you peck with a body hammer, (backed by a dolly block if possible) around the perimeter of the hot spot. As the metal cools you reduce the diameter of your hammering circle until the redness just leaves and move right to the center of the spot. This drives the molecular structure of the metal to the center of the shrink. A rag soaked in cool water over the shrink and the spot literally falls under your hand requiring lifting with either a cross pick, or needle pick hammer. Old school here boys if you've never been around a body shop atmosphere. You'd be surprised how many trade school graduates of auto body repair classes had never heard the term or practiced the art of "repair", vs. replace. Filling a 1/4 for instance with 3/8" of filler is not much of my idea of a "repair".SlobPurveyor of intimate unparalleled knowledge of nothing about everything.Oh yeah, also an unabashed internet "Troll" too.....
Reply:You cannot heat modern auto metals cherry red because it is all HSS, everything is structured now, I was taught to heat then tap surrounding areas as rog02 suggests, most people have gone the way of unispotter copper shrinking tips but if you are not careful again it is the "cherry red" situation changing grain structure and making coarse grain, fine. I now use a shrinking disk, a 10" stainless disc purpose made on  a big skill electric grinder a phenomenal tool for those even with little experience. This method reduces over working sheet metal and cracking. Best. Sent from my SGH-I747M using Tapatalk
Reply:The shrinking disc are all the rage these days.  Yeah they work, sort of.  Most are just a disc with an unfinished perimeter.  They are loud. They are prone to cracking due to the repeated heating cycles. I have a couple of them and they stay in the box most of the time.  The waffle disc are worse yet.You're right about a lot of the newer high strength deep drawing alloy bodies though.  They tend to crack if overly worked and replacement is the only approved repair.  I understand many insurance companies are now requiring special welding techniques in approved shops to deal with the modern alloys.Funny you bring up grain structure Pistol.  Why is it sheet metal guys tend to think about it and structure guys dismiss the basic metallurgy?RogerOld, Tired, and GRUMPYSalesman will call, Batteries not included, Assembly is required, and FREE ADVICE IS WORTH EXACTLY WHAT YOU PAY FOR IT!Dial Arc 250HFThunderbolt 225 AC/DCAssorted A/O torches