[TheForge] 8" hemispheres

[Bruce Freeman]

Don,

How about a variation on the technique Peter Renzelli demo'd for a
"deep drawn" copper vessel:
He made it of two pieces (truncated cone rolled from flat, and a disk
bottom) TIG'd them together, then hammered them to final shape.  Same
thing should work for steel, if you choose the appropriate welding
technique.

Why do they come out lumpy when you make them from flat?  Do you mean
"wavy" on the margins, or just not fully smooth?  I would be inclined to
hammer them from the inside with a round-faced hammer against the end
grain of a log.  (Hot, of course.)  Then planish them from the outside
against a large, smooth sphere, if possible.  Else, planish them from
the inside in the same log.

Of course, spinning is another option.

Bruce
NJ

>>> PlumDon at aol.com 10/24/2004 8:31:36 PM >>>
I have been trying without any success, to get some 8" hemispheres in 

14-16g. Many of the architectural ironworks suppliers offer an 8" hemi
in 11g.  I'll 
bet they all get them from the same place and prices range from $15-26.
But  
having no luck finding anything in the lighter gauges. None of these
have  
responded to my request for lighter gauge hemis. 
 
Anyone have any ideas on where to get some or a quick way to make them?
 
Banging them out of a 10" disc with big wooden and leather mallets is
too much  
beating of an arm already in bad shape. Plus they come out a bit lumpy.

 
Much appreciate any ideas. 
 
Don Plummer
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