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  #1  
Old 01-04-2023, 05:00 PM
Sbgunderson Sbgunderson is offline
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Default Hot or Cold Forming

Good evening and happy new year,

I am working on building a 1/2 sphere from 3/16” steel sheet. The patterns are all made. I don’t have much in the way of facilities or a place to make an insane amount of noise at the moment so what would be the best way to shape the metal?

Im planning on grinding a sledge hammer to fit the curvature of the sphere. Then I was planning on annealing the steel. That made me think, should I just hit it when it is very hot instead?

Thanks for your help,
Spencer
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Old 01-04-2023, 06:07 PM
skintkarter skintkarter is offline
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Hi Spencer - what diameter is the finished sphere?
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Old 01-04-2023, 07:04 PM
Sbgunderson Sbgunderson is offline
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Should have mentioned that, it is 3 feet in diameter. Right now I have it planned to be in 16 pieces. So each piece of sheet is roughly 24”x24” to start.
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Old 01-04-2023, 09:41 PM
skintkarter skintkarter is offline
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What I was thinking - segments and weld together. If you had access to an arbor press or fly press, I be prototyping a triangular segment pressed between two bits of round bar welded to a plate (so like a vee block) and ideally the arbor press would have a rounded end. Might need a couple of spare blanks to practice on to get the bend sequence right. Initial thoughts are to press the general curvature into the triangle first (cut a piece of ply to act as a radius gauge or you could potentially bend the blank over the gauge, if the gauge were beefy enough) and then tease in the circumferential shape. Might need another 'bottom die' with the rods a bit closer together for this second bit. Process should be almost silent and should be able to be performed cold. Noisiest bit will be grinding up the welds Let us know how you go and please post some pictures.
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Old 01-05-2023, 03:04 AM
Jaroslav Jaroslav is offline
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https://www.youtube.com/watch?v=U3WfX9f4okk
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Old 01-05-2023, 04:52 AM
Marc Bourget Marc Bourget is offline
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Then there's the "common man's" equivalent - Pullmax Doming Dies


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Old 01-05-2023, 05:28 AM
Jaroslav Jaroslav is offline
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Or in the heat.
https://www.youtube.com/watch?v=OniopadJNDY


Pullmax will not be enough for 5mm?
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Old 01-05-2023, 10:02 AM
Marc Bourget Marc Bourget is offline
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I was thinking process (shaping) not capacity.


My bad for missing that important point!


I was more interested in teasing you!
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Old 01-05-2023, 10:53 AM
Sbgunderson Sbgunderson is offline
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Thanks skintkarter and others. The press idea seems like it could work for my needs. Any thoughts on the size of the rods or how far they should be placed. Many thanks.

And if the Pullmax is for the common man, I don’t know what that makes me. Right now I have a large tent, sledge hammer and some sheet steel. I will get working on the press!

Thanks guys
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Old 01-05-2023, 11:38 AM
Jaroslav Jaroslav is offline
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I understand. I'm teasing too.

The point is that even a big hammer will be a problem. It would be possible to use, for example, a ball and the hole (tube) - as a tool. A simple hand press with a long lever. It's just a matter of effort and efficiency.
If the medical expenses for recovery after the hammer trip are worth it, send a photo of the result and the muscles on the hand.
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