I'm asking this purely out of curiosity. How thick does sheet
metal need to be to set stones in it?
It really depends on how big the stones are, but the truth is that
you can set stones in anything that's thicker than the girdles if
you're really careful. For flush setting, I would say 18 to 20 gauge
is probably the realistic limit for anything around 3mm diameter and
smaller (like the Bondanza pieces you referenced) but as
denverjeweler says, you can always back it up with a jump ring if
there's a compelling reason to go thinner. For bead setting or pave',
18 gauge (1mm) is about the thinnest I would want to work with when
setting up to 2.5mm diameter stones. For stones in the 1 to 2mm
range, you can get by with thinner sheet, but again, it really
depends on how careful you want to be cutting the seats and pushing
metal around. Go too thin and it's pretty easy to distort the piece
with the pressure required to do the setting work even if you're
really careful not to blow through the bottom with the setting bur.
When setting a one carat (6.2mm) round diamond, I would probably want
to be around 14 gauge or thicker, especially if there's going to be a
lot of bright cutting or anything.
I agree that the links look like they are fabbed or cast in hollow
sections with added bottoms. The tops with the stones are probably
around 1mm thick, maybe a tad thicker. Just guessing.
Hope this is what you were looking for.