I measured a length of half round sterling silver wire for a size 5
ring. I preped it, soldered it, then found that, once it was on the
mandrel, it was entirely too small....size 3. What did I do wrong.
Bill - The solution is ever so simple. Use your chart for the length
of the wire and add 3 times the thickness of the shank to the length.
That will compensate for the thickness. What happens is that the
dimension on the chart is the outside circumference of the ring. You
need the inside circumference. If you use one of the little six inch
jeweler’s scale/ruler, it mentions that you need to add three times
the metal thickness to the length of your ring stock.
While I’m on my soap box, I’ll add this: I hate wasting time fitting
bezel wire to stones, and even more hate the trial and error of
making an inside seat for a stone. I always calculate the bezel
length, and cut it. It fits 99.99 percent of the time. This works for
round stones and oval stones. Accurately measure the average diameter
of the stone - find the largest diameter and the smallest, add them
and divide by two to get the average. Next measure the thickness of
your bezel stock - 28 gauge is 0.35mm. Add the two numbers together
and multiply by pi - 3.15. Mark that length on your bezel stock with
a scribe and cut with a shear that yields a flat cut. Solder and
check on the stone.
Here is an example: For a 14mm round stone, the largest diameter I
found was 14.05mm, and smallest was 13.75mm, average diameter is
(14.05 + 13.75)= 27.80, divide by 2 = 13.90mm. Add the thickness of
the 28 gauge bezel wire, 0.35mm, for a diameter of 14.25mm, multiply
by 3.15 = 44.8875mm and cut a strip just a hair smaller than 45mm.
I use a dial caliper that I purloined from my husband’s bench many
years ago. It measures accurately to 0.05mm and can be interpreted to
0.025mm accurately. I sometimes use a digital caliper, but I prefer
the dial - sort of the difference between digital and analog watches.
When you need the length for an inside seat, simply subtract the
thickness of the inside seat wire from the diameter of the stone and
multiply by 3.15.
You will discover after having done this a couple hundred times that
you will have a repeatable tendency to cut or measure slightly short
or long. Just make note of what you do and compensate appropriately.
Judy Hoch, from Denver where the weather is outstanding for bicycle