I want to make a ring with a cabachon stone. I know how to measure
for the bezel and the back plate, but I can't figure out how to
measure the ring shank (12mm double 1/2 round wire). Is there a
gauge or measuring device that will help me calculate how much
silver I need?
I could interpret this several ways. A) You want the shank to come
up to meet the edges of the bezel and NOT continue under it B) You
want the shank to go under the bezel only a certain amount C) you
want the shank to totally encircle the finger with the bezel on top
In both A and B you would have a D-Shaped finger opening. A
consideration here would be comfort...if the bezel is very wide, not
only will it throw off your finger size 'feel' you may encounter a
problem getting the ring off and on. The advantage is that if its a
tall stone the ring would be lower in overall height making it more
practical to wear in the real world.
In C you have a complete circle to the finger opening. My own
judgement is that this makes a more aesthetically pleasing product,
but that is really open to interpretation.
In any event, since you're working in silver, cost is not so much of
an issue. I'd suggest making a full round shank, make your bezel and
then see how you think they should fit together. This way you keep
all your options open until you can see how the 'physicality' of the
components work together. If you opt for A or B at this point its a
simple matter to file or saw a flat on top of the shank. If you go
with C I'd still consider making at least some sort of flat so that
you get a better join and it doesn't look stuck together.
As far as actual measurement of raw stock.... you can buy a ring
mandrel with a length gauge stamped into it. You must add to the free
length the thickness of the stock. Suppose the gauge says for the
finger size you select that length should be 54MM(size 6) and your
material thickness is 2MM then you would cut the wire to 56MM. This
allows for the larger outside diameter of the finished shank. If you
want to make A or B this way, simply subtract the length of the
opening at the top.
But it sounds like you're using some heavy gauge wire which will be
difficult to get the curve at the ends. You could use ring bending
pliers but it may put deep gouges in the material.
On the whole, in this case, it sounds best to make a full shank then
cut away what you don't want. Just my opinion.
You can find length gauges in catalogs. If you'd like I'll send you
something to suffice in the meantime.