Forming metal caps

TW:

You may want to look at a "dapping block" which uses punches to drive sheet metal into correspondingly sized hemispherical depressions. You could cut the hemispheres out and solder on a ring for a neck which would fit over your tube. That could could be threaded or otherwise fixed onto your tube if you want to go that far.

If you cut a circle of excess material in the dapped sheet around your hemisphere, keep the punch in place and hammer said surrounding material down to form a neck assuming the diameter of the punch shaft is a little larger than the diameter of your tube.

Look up an image and the words will make more sense. Dapping blocks are appropriate for malleable metals. Harbor Freight is one site you may want to check for an inexpensive offering.

If you have access to a punch press or more involved tooling, there are other options.

Regards,

Edward Hennessey

Harbor Freight calls it a doming block

He's making pentagonal tanks...

Here is how to form the ends:

Make a male punch of seasoned maple, birch, beech; oak is too coarse grained. Make its dimensions the same as the outside of your tank body. Be sure to give those edges around which the metal forms a generous radius... bigger is better.

Obtain a piece of polyurethane rubber medium hard, 1/2" thick, and fit it into a pocket on a steel plate, ie. build a stout metal fence around the rubber pad.

Place polyurethane pad and base into a 10 ton hydraulic press, place your sheet metal blank onto the pad, place punch on top, and apply pressure judiciously.

The blank should be prepared such that it is 3/16" or so wider all around the punch.

Trim to fit.

Any remaining wrinkles can be ironed by gentle hammering onto the punch.

Walla!

Wolfgang

Metal spinning on a lathe?

I made some CPU water cooled heatsinks using wood male and female dies. But I was using copper , not steel. Had no problems with wrinkles or ripping. It was a while ago. I think I may have used a three part die. A female die, A flat plate that clamped onto the female die that held the copper to the female die. The flat plate would have a hole for the mail die to go through. That would give you a part with a flange on it that you would probably want to remove.

Dan

Here's a cheap dapping block set, might work on steel if it is thinish and mild:

You might have a look at electroforming.

Dan

" snipped-for-privacy@krl.org" fired this volley in news:571be158- snipped-for-privacy@r3g2000yqh.googlegroups.com:

Me... I'm going to try hydroforming at my first opportunity. That looks to be the metal version of vacuum thermoforming, and I love the idea that I might be able to make detailed sheet metal shapes without complex dies and punches.

LLoyd

As an alternative: Would Coke cans work? You can sand blast the printing off of Coke cans with baking soda. I would think a small sand blaster using canned air (like you spray out your computer keyboard with) should be relatively easy to make. Cut the Coke cans to size. And then TIG weld the two halves together. Probably would work best with a backing ring (also cut from the Coke can) for the weld. TIG on the fittings.

The aluminum construction would be less weight in an RC airplane. Dave