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I Forge Iron

Ideas on how to build a stainless steel hollow ball with a high quality mirror polish?

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Asma -

I am not trying to detour you from this, but there are some considerations that would have to be dealt with.

You will have your work cut out for you with that project, Easy / Least complicated? No easy way, the larger the project the more complicated, let alone very expensive, both in time and materials. If you try to use thin mat'ls for sake of weight - you have major handling issues with large floppy pieces and forming ( large hydraulic press with dedicated top and bottom dies for achieving the correct radius), or heavier - you have issues with forming ( large hydraulic press with dedicated top and bottom dies for achieving the correct radius) and handling large heavy pieces. For a sphere that size, the forming has to be spot on so when it's all welded together it is a constant radius. Then comes the polishing - lots of costs in different grits of abrasives and time involved to get a mirror finish - With a mirror finish, any imperfections on fit-up during welding will show up like a sore thumb. Fit-up of the welded joints will have to be less than a 1/8 of the thickness of mat'l so you have thickness to grind smooth and still have plenty of base metal for the joint. Those types of sculptures look fabulous when all done, but require a vast amount of cost, equipment, and expertise to make them look so simply done.

I would like to hear more about the project you have, involving such a sphere.

There is a page in the shinydecor site that gives you a rough idea on the process of how these spheres are made.

It appears that they "inflate" the welded shape to get the sphere shape.



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JHCC - The Cloud Gate link is a good article, this is a good example of what something large costs - The original cost estimate was $9 million, but project complications led to a final cost of $23 million. http://www.billslater.com/cloudgate/

I realize this is a bit larger than Asma is referring to but it helps to put size vs. cost into prospective.

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There is no easy, inexpensive route for this project unless you can find one surplus somewhere.

Have it done on a large spinning lathe. But that will require a big spinning lathe, forms, and big sheets of stainless. Getting the weld seam smooth will be the biggest hurdle.

Find something already round (float,etc) that you can have chrome plated. 

Some propane tanks have spherical ends welded onto them. Cut them off and weld them together. Then plate.


HAHAHAHA! The last picture in the above link states that they do custom suffocating for free.....

I wonder if they are just pumping water into them to inflate the ball. 

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You might also check into a web image search on "Lapidary sphere machine" of an alternative idea about polishing spheres.  The method shown in the earlier link/video shows just how out of spherical those large balls actually are and a polishing system similar to what is done for stone will result in a much more spherical product (if the walls are thick enough to take it).  Might be over-kill for your needed product, though.

Stainless is a pain to mirror polish and will haze over time also so you might consider a path of pre-polishing and then plating or some method of electro polishing rather than fully mechanically polishing.  Again, depends on the result you are seeking.

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9 hours ago, jeremy k said:

It would not take a whole lot of pressure to expand but the explosion hazard would be Huge.

Oh contrare Jer. (Sorry I couldn't resist, I used to hear that all the time) Anyway, there is zero "explosion" hazard inflating hollow forms hydraulically and if you do it submerged i a tank of water you don't have to worry about a pinhole slicing you like a razor does a banana. You could use a pressure washer if you have time.

Asma: I doubt strongly there is an easy or inexpensive way to produce polished hollow stainless steel spheres this size. We could've in Father's metal spinning shop but would have to sub contract for welding and polishing. Just our part would've been REALLY expensive, especially for a one off or limited number.

Frosty The Lucky.

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6 minutes ago, jeremy k said:

Frosty - Sorry - You are correct, I was thinking inflating with air out in the open.


Don't be sorry, a lot of artists inflate hollow ware with air in the open it just wouldn't work on this scale, not safely at any rate. 

In the '60s Popular Science carried articles about inflating asteroids by drilling to the center, packing in ice, welding a thick plug and heating it with concentrated sunlight. The bright red hot asteroid would soften, the ice would boil and inflate the asteroid. 

Funny how a couple decades in space brings out some of the difficulties involved in doing anything is space. There's a good John Ringo series that does a lot of asteroid inflating, first book is, "Live Free or Die."

Frosty The Lucky.

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