Originally Posted by
Dennis
Dear Nic,
By this time you will have had lots of advice, so I should just like to offer a summary . If you look back to earlier this year, you will see that Peter outlined a method not involving any measuring, while I prefer to use electronic callipers. That is a matter of choice. One problem with callipers is that people have difficulty in getting a true reading because they have to be zeroed each time they are turned on, much like when you use scales for weighing.
Gemstones of a nominal size will vary even out of the same packet. So say ‘3mm dia.’ stones might measure 2.9, or 3.3. This can make a difference to your choice of tubing. You would aim to have a rim to push over of about 0.2-0.3mm in thickness, so for a 2mm stone you might select 2.4mm outside diameter tubing. That said I much prefer to have a selection of tubes near the size I am after, as tubes can also vary from batch to batch. You could buy say, 6cm of each, which in silver would not be very expensive. That would even allow you to have a practice run, with a cheaper stone, such as a CZ. They can easily be cut out again with a saw and you would only waste about two mm of silver. Not a high price for the experience.
What size tube settings you make will depend on the size of tubing available, the size of burrs listed and your eyesight. I baulk at anything below 2mm and generally make my own bezels above 6mm.
I start by holding a long piece of tubing, insert the burr, and open up until the girdle of the stone just fits inside. Later the table of the stone will have to be more or less flush with the rim, giving some metal to push over. I do not complete this until after soldering, because thin tubing tends to widen with heat. Then I cut off the length I need. After soldering I make my final adjustment using a burr with a touch of oil in a pin vice. Some people happily use only round burrs, but I prefer to finish with setting burrs, to get a more positive feel. For size, I refer to the Cook Book.
When setting smaller stones I squeeze carefully with round nosed pliers, just above the girdle of the stone. Squeezing below would make the stone pop out. Kind regards, Dennis.
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