Calculating bezel length for oval cabs

Jewelry Discussion
21

I just put some doublesided Scotch tape on the back of the cab,
stick it down on a flat surface, cut one end of the bezel strip
square to the end, wrap it around the cab and mark the point where
the ends overlap plus about 1/32" and cut it square across the end of
the strip. Check the fit, make sure the ends are square to each other
and finally solder it together.

Bob Rush

22

Not quite sure what the purpose of wrapping something or another
around the stone than laying it out and remeasuring the bezel to this
what ever it is. And why waste time doing math every time you make a
bezel? I make a few thousand bezels a year doing all that would ad
untold hours of work. Wrap the bezel aroung the stone mark it and cut
it. So what if you have to trim a coumple millimeters off its still
the easiest way and if your worried about wasting that small snippet
of silvet drop them in a jar and use them when you need to make
balls. Dave Owen

23

Thanks everyone for the feedback. As I set more and more cabs, Iā€™m
sure Iā€™ll find the method that works for me. So far, after using
formulas correctly and the online calculator correctly the bezel
length has come out incorrectly due to the oval cab not being
perfectly oval by, I suppose, any mathematical definition. By simply
wrapping wire around the cab, I have a bezel length that is closer to
perfect length than any of the formulas have given me. Perhaps I
should have added that my cab is not calibrated.

24

Or, if one were a smartass with a CNC machine, one could write a
single Python program to emit the necessary GCODE for any given major
and minor axis, then let the machine cut the ellipse out of aluminum.

I believe there are suppliers out there who offer machined solid
elllipses out of tool steel. They are expensive.

Who wants a set out of aluminum, at just a buck per ellipse?

Andrew Jonathan Fine

25 
This difference in shape makes the perimeter dimensions of them
different. Thus if you use a mathematical formula to determine the
perimeter, the bezel may fit on some but not on others.

I guess some of you instead of reading my post, simply skimped the
section describing formulas and when and how to use them. I am not
going to repeat myself, except saying that right formula works all
the time. But if someone wants to continue to wallow in ignorance,
than who am I to stop it. It is ok to use whatever method one finds
comfortable. It is not ok to dream up deficiencies in other methods,
just because one does not understand it.

Leonid Surpin

26 
I do not comprehend why anyone would do anything but wrap the
bezel around the stone, mark it and cut it.

Iā€™m sorry if you donā€™t understand this method. Iā€™m so bad at math,
even my bank has to correct my deposits on occasion, and my father
is a math genis. Iā€™ve had so much trouble trying to find a good way
to calculate the length of bezel using tape or a stripe of paper and
ended up having a real difference in the bezel length, frequently
having to planiish to stretch bezels to fit. Iā€™ve actually gotten
very good at getting the right length of bezel strip to cab size.
Being math-challenged, I compensate in other ways that works for me.
As for faceted stones, Iā€™m still pretty good at the overall size, but
another trick I do with small stones is to measure the girdle of
faceted stone or cab with calipers, lock the calipers, and then
position the calipers on the bezel mandrel, mark with a pencil where
the calipers fit. Wrap bezel strip around the pencil mark, make
another mark on bezel, and cut. It comes out pretty accurate for me.
Bezel setting is a subject Iā€™m very picky about, and Iā€™m particular
at how bezels fit. Letā€™s face it - not all of us can work like 95%
of the population and have to develop some odd tricks to deal with
challenges. Iā€™ve had to simplify some proceduares to mke it work for
me. I think a little differently than the general population, much to
my annoyance. Iā€™ll shut up and just lurk in the background for a
while.

Joy

27

exactly. Why do we need math to make a bezel? It fits well if the
metal is wrapped tightly around the stone. No formulas are needed.

28

This year Iā€™m going to have both thumb joints (base of the thumb)
replaced. Back when I thought Iā€™d never get old or start to wear out,
Iā€™d do something like just wrap the bezel around the stone. Now the
extra minute it takes to wrap tape around the stone, mark it, add
metal thickness, transfer the marks to metal, saves me hours of pain.

Kelley Dragon

29

Joy,

Youā€™re overcomplicating the process. Itā€™s not a math problem. Take a
piece of paper, wrap the stone and mark it, then add the metal
thickness to that length. Itā€™s really that easy. If you have some
cardboard the same thickness as your bezel wire you wonā€™t even have
to add the metal thickness!

Jeff Herman

30 
I do not comprehend why anyone would do anything but wrap the
bezel around the stone, mark it and cut it. I am not good at math,
I am good at fabrication.

Right Richard.

Wrap the metal round the stone. If too small think about planishing,
too big and cut some away. Eyeballs and gut feeling only. Even if I
have to start over again it is faster than digging out the right book
or math formula.

jeffD
Demand Designs
Analog/Digital Modelling & Goldsmithing
http://www.gmavt.net/~jdemand

31

I have been setting cabs for decades and not once have I used a
formula or wrapped a wire around the stone and used it to measure my
bezel material. I think the problem with formulas is the difference
between engineering and architecture. You can dream any design or
method of construction up but making it with the available materials
is the challenge.

I wrap the bezel material itself around the stone, mark it then cut
it. I try not to let the bezel material slant in but stay
perpendicular to the widest part of the stone. This requires having
more bezel material than stone length but in silver that is not
usually a problem for cost, a dollar or two more versus the wrong
length is a good trade off to me. Using the bezel material itself
eliminates any differences due to thickness of the bezel material or
any irregularities of the stone. After I make my cut I solder the two
ends together and form it to the stone, the bezel doesnā€™t have to
look pretty prior to soldering the two ends together. If I cut to
short I can stretch the bezel on what ever mandrel is closest to the
stone shape, if it is cut too long then I can cut a piece out and re
solder. With practice ( a hundred or so bezels?) cutting the proper
length is not a problem.

Sam Patania, Tucson

32

I know this is going to sound like such a newbie question to most of
you, butā€¦ would any of you kind folks mind sharing your technique
for cutting the bezel wire square? Iā€™ve taken several silversmithing
classes by now and every instructor seems to have their own way of
doing things. One of the reasons for taking classes for me. I still
have not perfected a technique for this very basic skill!

Thanks for all who post!
Mary Rose Mcquillan

33

At this point, Iā€™m thoroughly pissed off at some of you, who are
"appalled" at how I dare wrap a bezel strip around a cab, mark it,
cut it, file it and solder it.

That point is, every single person has a different way of processing
info and doing it. Some of us are math-challenged, some of us have
trouble doing things the conventional way. Therefore, we develop
ways to work around it. I need to work smart, efficient and in a way
that also doesnā€™t hurt my already over abused hands. Thus, the way
of wrapping bezel strip around cab, marking it, cutting it, filing
and soldering is extremely efficient to me, and increases my
productivity. If too small, planishing takes care of it.

I canā€™t knit wire with a crotchet hook to save my life, but I can
make really nice Viking knit chains and woven chains. Itā€™s just a
matter of finding what technique works for you, as opposed to what
you were told to do, or what it has be done, decade after decade.
Iā€™ve spent half a lifetime trying to work smarter and more
efficient, for Iā€™ve had so many repetive hand problems from the
"traditional" methods. Iā€™ve also had to retrain numerous students who
were taught all wrong, or who had teachers who really shouldnā€™t be
teaching jewelrymaking in the first place.

By the way, several readers of this forum have told me, offline, my
way of doing bezels was a godsend, so Iā€™m not crazy. However, Iā€™ve
decided to leave this forum, and just work and teach the way it
makes most sense. Iā€™m just too pissed off.

Joy

34

Mary,

This is quite premature, but I have invented the very tool you need
to make a perfect 90 degree cut on your bezel stock, regardless of
width or thickness. Eurotool will be manufacturing and distributing
it sometime in 2012. Eurotool and I will be promoting it once it is
ready to market.

Jay

35 
would any of you kind folks mind sharing your technique for cutting
the bezel wire square?

I believe many people just cut it with nippers and leave it at that.
Iny experience, even the best flush cutters leave an end surface
that is not totally flat. So, fussbudget that I am, I file both
ends. To make sure the filed end it truly flat, you can use a mitre
cutting jig, or hold the bezel in the jaws of pliers with straight
edges, with just the part you need to file off sticking out, and
file down flush with the plier jaws.

This tip was published both in Art Jewelry magazine, and on the
Contenti site, I think with a picture, if this description is not
clear.

Noel=

36 
I believe many people just cut it with nippers and leave it at
that. Iny experience, even the best flush cutters leave an end
surface that is not totally flat.

Instead of nippers, I use snips. Generally, just the same ones I use
for cutting solder sheet. Pretty much any snips that do not have
serrated edges. The snips produce a cut that is smooth, but slightly
angled from one side of the sheet to the other, and often slightly
curl the sheet. When you cut the bezel, however, you first cut one
side, then flip the whole thing over so youā€™re cutting the other
side with the cut end to the same side of the snips. What that does
is give the two slightly beveled or angled surfaces, an opposite
angle, so they essentially mate, kind of a slightly mitered joint. So
long as you cut straight across, the two ends can match perfectly
with no filing required. As I said, some snips slightly curve the
sheet, but this is quickly fixed with a quick squeeze with a pair of
flat pliers. Overall, fast and easy. Easier, I think, than filing the
edges of thin bezel wire. Of course, sometimes Iā€™m doing bezels from
much heavier stock, such that theyā€™ll likely be set with a hammer and
punch or hammer handpiece, etc, not just a burnisher. These of
course, donā€™t get cut with snips. They can be cut with nippers, but
then youā€™ve got to file. If youā€™re good with a jewelers saw, you can
get close enough fitting ends with just saw cuts, not needing to
file the ends.

Peter Rowe

37 
Thus, the way of wrapping bezel strip around cab, marking it,
cutting it, filing and soldering is extremely efficient to me, and
increases my productivity. If too small, planishing takes care of
it.

The first rule of working with precious stones is always to protect
them. Never place gemstone or use it in a way that it can be damaged,
no matter how remote possibility is. Handling gemstones as described
above will get one fired on the spot, in any shop handling gemstones
of some value. That said, letā€™s put it aside for the duration of
further discussion and look at the process itself.

Facing with a gemstone, the first question is how thick the bezel
should be? If we are going to wrap it, cannot be too thick. Letā€™s
take 0.5mm. After wrapping and cutting, the bezel will be too large
(there is no way around it), so it has to be trimmed. The question
is by how much? Since we have no idea of what the actual length of
out bezel is, nor do we know what is the circumference of the stone
is, so we are going to take a guess. While it is possible to guess
correctly, the odds are against it. The result will be bezel too
large or too small.

If bezel is too large, the process is repeated until unescapable
result of too small. So we have to planish it to size. In doing so,
we mar the surface with planishing marks and we thinning out our
bezel. When we get to the size, bezel will needed to be filed to
restore the surface. The question is what will be the thickness of
bezel at that point ? I would say 0.4mm if we lucky, could be as bad
as 0.35mm. But letā€™s go on. Remember, we cannot file on the inside (
if we do, bezel will get too large again and even thinner ), so
inside surface is somewhat rough. That means we cannot slip the
stone in place and have to rely on stone falling in place, which by
definition require bezel to be larger than the stone.

To set the stone, we have to actually reduce bezel circumference
above the girdle, but at this point we do not enough thickness to do
it, and such settings invariably buckled all over and do not look
attractive. The name is ā€œchoppyā€. By the time we done, such bezels
are paper thin. Some will not even survive polishing.

Some may say the solution is to start with thicker metal. The
problem is the thicker the metal, the deeper the handling marks and
etc. The result may actually be worse. But that practice of wrapping
metal around the stone does explain popularity of using epoxy in
setting bezels and similar methods. Frankly, the whole process is
quite obscene from the point of view of craftsmanship.

The whole thing has evolved on the account of math phobia. I wonder,
what has happened to our civilization. Ancient Greeks were able to
use their brains to create Mathematics out of simple observations and
thinking logically. We should be much better than they were! But
after several thousand years we deteriorated to the level that idea
of substituting few numbers in a formula scares us. This is really
sad.

Leonid Surpin

38 
By the way, several readers of this forum have told me, offline,
my way of doing bezels was a godsend, so I'm not crazy.

This seems to happen oftenā€“Readers responding offline in agreement.
There have been times when those ā€œbelow the radarā€ posts supporting
an opinion (that has sometimes been unfairly and even nastily
pilloried on the forum) would sure be welcomed.

I wonder why those comments of support arenā€™t aired publicly?

Snow is finally gone in Seattleā€¦Andy

39 
who are "appalled" at how I dare wrap a bezel strip around a cab,
mark it, cut it, file it and solder it.

Well, yeah Joy itā€™s the pits. It comes from jewelry schools, once
again, I believe. It also comes from students using calibrated,
machine cut stones that have exact dimensions. In the real world it
just doesnā€™t seem like a difficult concept to just make a bezel for
a stone. If you canā€™t wrap a piece of metal around a stone with
reasonable precision, then you need to learn how. And ā€œwrappingā€
might mean using a pair of pliers on heavier stock to mate the
contour around the stone, bit by bit. And if you canā€™t cut the end
off of a wire square and then pick up a file and make it flat and
square, you need to learn how to do that, too. This is all
fundamental stuff.

40

Mary,

I know this is going to sound like such a newbie question to most
of you, but... would any of you kind folks mind sharing your
technique for cutting the bezel wire square

  1. One way is to cut the wire a bit long and file the ends square
    using a needle file,

  2. OR (and this is what I do), wrap the bezel wire around the cab
    and let the end pass under the roll so there is an overlap. Mark the
    correct length with a sharpie NOT at the end of the wire, but a
    little past it. Mark at the top of the wire so you get some ink on
    both the end and the overlapping wire. Remove the wire and with it
    still in a loop and overlapped, cut on the mark so that you are
    cutting both ends of the wire as they are overlapped. Even if you
    donā€™t cut exactly perpendicular to the length of wire it doesnā€™t
    matter because youā€™ve cut both ends at exactly the same angle and
    they match up!

Denny Turner in San Diego