Tension ring setting.

[Sassoon]

Hi I'm looking at making a tension ring with a 4mm emerald cut stone, but I'm not sure what size or type of burr I'll need,any help would be appreciated. John

[Dennis]

Hi I'm looking at making a tension ring with a 4mm emerald cut stone, but I'm not sure what size or type of burr I'll need,any help would be appreciated. John

Hi John, not all emerald cut stones of a nominal value are alike. Some are thicker than others, but you might start by trying a bearing cutter about 1.20mm in diameter, Cookson 942 020.

Now I hope you will not mind further unsolicited advice:

1. An emerald cut stone is not ideal for your first try. Round ones are easier.

2. The ring needs to be work hardened by expansion on a ring stretcher, or a mandrel.

3. When you cut it a gap will open, due to its springiness. You will be the judge of how much gap you will eventually need, depending on the type and hardness of the metal. This will also affect the sizing. One mm gap will increase the ring size by roughly one English Size. This must also be considered in stage 4.

4. Having cut the bearer, you will then open the gap sufficiently by pushing it along a mandrel until the stone can be inserted and hope it will close again to resit the finger pressure when it is put on. The pointy base, or culet, should not touch the finger.

Don't hold your breath. Companies specialising in this have equipment to measure the tension, and generally use gold or stainless steel for the ring. Even then they admit to a failure rate.
If using silver, you are very limited as to the amount of spring you can achieve and it is best to use a very thick or very wide section. Dennis.

[Sassoon]

Thanks very much Dennis
for the info, I think I'll take your advice and start of with a round gem setting. John