Hi, I am just starting out on my jewellery career and I recently made
a Russian wedding ring (normally three different coloured gold bands
linked together) from which I read the instructions in a book. The
problem is that although I followed the sizing rules in the book, it
turned out no where near the size I had expected. Can someone please
let me know how I calculate the length of rod needed if for example
the ring circumference is 66mm what length do I have to cut the (half
round rod) if it is 3mm thick
Thanks in advance for your help
It’s a bit more complicated than that. Since the rings roll over each
other, each band needs to be larger than the actual ring size, on an
American ring gauge, and using 3mm x 1.5 mm thick half round stock, I
have found that the size difference is about 1 1/2 sizes larger. That
would be about an extra 4.6mm or so.
Hope this helps
Rick Hamilton
Dear Paul, First figure the diameter which is: circumference / pi: (66
mm / 3.14 = 21.02) Then length needed will be (diameter + thickness) x
pi. (21.02 mm+ 3 mm) x 3.14 = 75.42. For bands over 4 mm in width
generally add 0.5 mm to length.
Alan Revere’s Professional Goldsmithing book has a great chart for
cutting lengths from size 1 to 14 in thickness’ from 0.8 to 2.6
calculated out along with lots of other useful
Best regards,
Marta
paul - someone has probably already answered this, but i mark off the
mm measurement onto a 1/4 inch wide strip of cardboard or magazine
insert, cut it at the mark, tape it & slip it onto my ring mandrel
for the standardized ring size, which has sizes broken into 1/4s.
from then on i work on the mandrel at that size. for customers
sending their ring finger measurement by mail i have them cut a 1/4
inch wide strip from an old business card or a torn-out magazine
insert, roll it up once, wrap it around the largest knuckle on the
proper finger so that there are 2 thickness on top & stick a pin
through both. they then send that to me; the vagaries & inaccuracies
of measuring rulers or tapes that people have on hand, misremembered
sizes, etc., are all eliminated by this method that treats the length
as a cipher rather than a possibly inaccurate measurement.
good luck -
ive
Dear Tom, I have much success calculating the blank this way. I check
the size of the ring. Than I measure my ring mandrel at a half size
smaller than the ring has to be. Take that measurement and add the
metal thickness. Once I get that answer I multiply it by 3.1416
(pi). That’s the length of the ring blank. I like to stretch it up
on a ring stretcher to make it nice and round. It makes it nice and
hard too. Another benny is I don’t have to use as much metal.
However slight. It adds up over time. Example: 16mm (diameter for a
size 6)+ 2mm(standard thickness for a wedding band)3D 18 x 3.1416 3D
56.5488. Round it up to 56.55. Now if I want to make something like a
bezel with a seat I would do the same thing measure the stone add the
metal thickness and multiply by 3.1416. To make the seat fit in the
bezel I already know the diameter of the stone so I would take the
stone size subtract the metal thickness and multiply by 3.1416. It’s
always good to be a little short because the metal stretches when I
tap it on the mandrel. Sterling silver is the hardest to calculate
because it stretches so much. Good luck, Hope this helps, Johnny I