Setting non calibrated stones

Hi All,

If you have a stone that is not calibrated, say a 6.5mm (and you
didn’t have a 6.5mm setting) would you be more likely to use a 6mm,
or a 7mm setting? I’m currently using a 7mm but I have too much metal
left after bending the prongs… I guess I could take it off with a
cup bur or something but I was wondering what you all do…



Dear Craig,

Take a deep breath, and order a 6.5 mm setting.

If you take a little extra time to do the project correctly from the
beginning, you’ll have a far easier time of it, and a better looking
end result.

In my experience, setting a stone in a too-big setting results in
the stone looking like it crashed into the piece, because the
setting is all buckled in around the stone.

Just my humble opinion.



First, I have to mention that I have noticed that the size of a
prong setting that a supplier lists for a given size stone may vary
from each supplier. Some are larger, some smaller. That said, let’s
assume that the head we’re talking about came from Stuller, a major
US supplier. A 6.0 mm round stone will sit right at the top of a 6mm
head. After you cut the seat, the stone will be set near the tips of
the prongs. If you want to set the stone high like this, that’s fine.
If you wish to set it lower, I would use a ball punch to slightly
spread the prongs apart. The punch must fit low in the setting, near
the base. I want to spread the setting at the base of the prongs, not
just bend them out.

If I had a stone like you have, 6.5 mm, I would choose a 6.0 mm head
and spread the prongs. If I wanted to set the stone low, I might
choose the 7mm head instead. A 6.5 mm stone is a calibrated, and
common, stone size so you should not have a problem finding a head to
fit. Let’s say you have a 6.7 mm stone: I would still choose a
smaller head and spread it.

I once worked with a setter from Van Cleef and Arpel in New York. He
routinely spread every head that they used. He preferred them with
slightly more seat under the stone and a slightly thicker prong at
the girdle. I started setting my prongs that way, and I must say that
I have had fewer loose stones because of this. It is a VERY SLIGHT
difference, but it seems to give a lot more strength to the prongs.

Here’s another reason to vary the angle of the prongs: Let’s say
that you have to construct a 5-stone ring. The center stone is 8.0
mm, the side stones are 4.0 mm and 2.0 mm. Draw a circle that is the
size of the ring you wish to construct. Draw the outside diameter,
then draw the stones in place. Now, draw the angles from the edge of
each stone to converge at the center of the ring. You will notice
that not all the angles are the same. If the ring is a size 4, for
example, this will be really exaggerated. In my work, I will adjust
the angles of each head so that they all converge at the center. I am
doing high-end custom work, and I charge accordingly. If I worked at
a volume discount store, I would merely file the edges of each
setting so that they fit in a roughly graceful arc.

I realize that I may not have answered your original question, and
have opened up more questions along the way so that we are more
confused now than we were before, but at least we are confused on a
higher plane… :slight_smile:

Happy Holidays!


Douglas Zaruba
33 N. Market St.
Frederick, MD 21701

setting a stone in a too-big setting results in the stone looking
like it crashed into the piece, because the setting is all buckled
in around the stone. 

I agree with Susannah’s assessment that using a setting that is too
large results in not only a poor looking setting but also one that is

On the other hand, using a too small setting can produce the same
results. The prongs usually spread too wide to achieve a solid
purchase on the stone’s girdle, weaken the prongs and often results
in a lopsided setting.

One has two choices when faced with this problem; create a custom
setting…not too difficult a job after a bit of practice, or follow
Douglas’s suggestions. Personally, if time is a factor or one’s
skill level does not include making a custom setting, I would follow
Doug’s way! (Sounds like a new philosophy doesn’t it?). Very nicely
explained Doug.

Cheers from Don at The Charles Belle Studio in SOFL where simple
elegance IS fine jewelry! @coralnut2