[TheForge] copper balls

[Jay Hayes]

Randy,

I take it that you actually want to make a couple hemispheres that will 
be hinged together to make the BBQ. To shape the hemisphere first cut a  
copper disc larger than will be needed to make the part. Then start 
hammering the center area of the disc over a shot bag, sand bag or 
hollowed out stump. This is to stretch the metal. As the edge of the 
disc starts to wrinkle form tucks around the edge. Metalshapers use a 
shop made tucking tool to assist making the tucks. Then the tucks are 
hammered down with a hammering technique that forces the metal into 
itself that causes the edge of the disc to shrink. The stretch and 
shrink causes the flat disc to start to take shape. At this stage it 
does not have to be pretty. The lumps and bumps will smooth out. It is 
important not to let the tucks fold over or to cause the metal to tear. 
Copper work hardens quickly and needs to be annealed when it feels 
stiff. The rough shape is then planished out to smooth the surface. A 
pneumatic planishing hammer or English wheel are usually used to make 
quick work of this. A radius gage is used to check the shape until the 
desired size is achieved. Copper works fairly easily but the right tools 
make work even easier.

Jay Hayes


R.C.Mundt wrote:

>Talked to a customer today who wants 2 copper balls for his patio 30"-36" in diameter.  One will become a Bar-B-Q and the other an ice bucket.
>Has anyone had any experiance forming anything this big?
>All I can think of is raising which sounds like a ton of pounding or spinning on a setup similar to Mike Spencers air hammer power plant, big form and copper disc bolted to an axle.  The latter sounds half scary and would also be quite a bit of work even before moving any copper.
>Any suggestions wil be appreciated.
>Randy Mundt
>
>
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