"Determination of Ring Sizes" by Brepohl mention an apparatus
for soldering stone set rings [fig 13.11d.]
http://www.ganoksin.com/borisat/nenam/ring_sizes.htm Could you
please tell me where i could buy one of these.
I assume you're referring to the tool shown in fig 13.11.
I've never seen one in any tool catalog, but all is not lost.
You can make your own unit that will work just as good. Get a small
metal container (Altoid box or similar). Fill it to the necessary
level with fine sand. Insert the ring to be soldered & add water to
the sand. The water will keep the stone/s cool & the wet sand will
keep the ring in the desired position. If it's a prolonged soldering
operation, you may have to add more water to the sand.