Not exactly! Size 16 refers to a size used in Europe. A size 16
ring corresponds to a 16 mm inside diameter of the ring.
Only, at least according to my sizing sources, in Germany. There
are more than one european standards for ring sizes. Standard metric
sizes (used in 46rance, and i assume some other countries too) are
usually given as the circumference, not the diameter. That means a
size sixteen ring would be something like 5 millimeters across. A
nice jump ring, but not a finger ring. More common are size numbers
like a size 52, which is close to a U.S. size six…
size 16 is indeed also a standard American size ring, albeit a large
one. If you’re stuck with a mandrel that only reads to size 13, it may
help to know that each U.S. size increment is a difference of about
2.5 millimeters in circumference, so start with your blank for a size
13 length, and add 7.5 millimeters to that blank length to get a size
16.
Ring mandrels can be purchased in two usual size ranges. The best
mandrels I’ve found in the U.S., are the U.S. made ones by the Jarvi
company. You can tell them apart (in catalog photos as well as for
"real"), because the handle portion is usually actually knurled for
better grip. The standard Jarvi mandrels go up to size 16 as the
largest size, and then they also offer a “large size mandrel, which
is a considerably shorter but thicker one, that goes from size 16 (I
think. would have to go look to be sure) to about a size 22, if I
recall right.) Many of the tools suppliers carry these, including
Rio, Swest, 46rei and Borel, and others. I seem to remember a price
of about 15 dollars or so. Unlike some of the foreign made mandrels
(often made in India or the like), the Jarvi mandrels are much more
consistent in sizing accuracy from one to another, and are properly
hardened and tempered. Good tools. The last one I bought also
included a little adhesive label with the standard ring shank gauge
printed thereon, since unlike some of the foreign made ones the Jarvi
ring mandrels don’t have that gauge stamped into the mandrel. The
Jarvi mandrels are also available as grooved, and their grooved
mandrel has a slightly shallower, but less deeply cut groove than
the foreign made one. And they also make some specialty versions.
You can buy one quite useful shape that’s the 'rounded square”, or
"cushion" shaped, as well as a sort of egg shaped mandrel. both
these are intended as ring mandrels, not bezel mandrels. Very
useful, though these special shapes are, sadly, not marked in ring
sizes.
Hope that helps.
Peter Rowe