cold shrinking

[metaldemonz]

hey I have a question about cold shrinking with hand tools(hammer and dolly) i'm trying tomake a gas tank top that has pretty sharp corners. I tried a hammer form but the metal just wrinkles and overlaps and does not shrink into it self any suggestions on what im doing wrong. thanks

[Neal Nicholson]

metaldemonz

Look in the Novice Sheetmetal Shapers section for a post titled Making a Tucking Tool you will find some info on shrinking tucks. The topic sort of side tracked into something other than the original.
Also go to the gallery section and find Wray Schelin's videos. Fire up the one on making a motorcycle tank 001 and watch what Wray does with the Helve hammer. As he stretches the metal in the middle, tucks form around the edges. He then switches over to a hard plastic pad under the hammer and procedes to crush the tucks. Notice the motion as Wray works around the tuck and from the closed end to the open end. The process is the same with a hand held hammer just a bit slower.

Neal

[snotzalot]

metaldemonz

Neal has made some good suggestions. Get yourself some scrap 20 ga. or aluminum and practice making some tucks and flattening them. One you have made a few tucks in practice your project will come easier.

Question what are the dimensions of the project and the size of the part you are trying to fold over?

[Bob Baisden]

hi metaldemon,

When the metal wrinkles, you could remove the hammer form and try hammering out the wrinkles (tucks) on a hard curved surface like a pedestal mounted anvil. When you hammer the wrinkles try to capture the tucks in the pattern Neal mentions.

Bob

[roberlt]

You didn't mention what kind of hammer you are using. When I do hammerforming I use a delrin tipped hammer and occasionaly a rawhide mallet to crush the tucks.
Seems to work.
Rob

[metaldemonz]

the part is 12" wide 15" long the flang i'm trying to fold over is 3/4" the metal is 18g. I was using a plastic mallet at first them switched to a steel hammer it started to work but I will try a raw hide mallet i have but it is very light. What exactly is a delvin faced hammer? now i'm on my way to the gallery to check out the videos. thanks alot for the help.

[snotzalot]

Try tuck shrinking the corners prior to bending over the edges.