so how do you order the right size of tubing from a catalogue for
that size of stone without the benefit of tubes physically in hand
to match the stone to?
I have done lots of tube setting, but usually with smaller stones,
say 2 mm No reason why you can not tube set a 4 mm stone. The trick is
to get a tube that will give you enough tube wall to provide a seat
for your stone as well as allow you to have enough left over on the
outside to push over your stone (like a bezel) to secure the stone. I
am assuming that the stone you want to set is round ie brilliant
cut. You need to measure your stone diameter with a calliper in order
to make sure that it is really 4 mm in diameter. The inner diameter
(ID) of the tube must be smaller than the stone diameter. The outer
diameter (OD) of the tube must be larger than the diameter of the
stone. For a 4 mm stone I would recommend a wall thickness of about
0.4 mm or more. This would mean that the inner diameter would be
about 3.6 mm and the outer diameter would be about 4.4 mm Wall
thickness is (OD-ID)/2
I looked in the Rio Catalogue The closest I could find was their
0.188" tube (item #100-905). Note the catalogue is in inches and not
millimetres Unfortunately, this tube is not suitable for a 4 mm stone
The tube has an OD of.188" (4.77mm), and ID of 0.156" (3.96 mm) and
a wall thickness of 0.016" (0.4 mm) This tube would be suitable for a
4.3 or 4.4 mm stone
I could not find anything in the Rio catalogue that would work on a
4 mm stone.
You will have to check other supply houses for a tube with the
dimensions that I suggested.
Good luck finding the tube you need.