How stone seats are modelled in jewellery CAD
A stone seat is the space in the metal where the stone sits. If the seat is wrong, the stone sits crooked, rattles or cannot be set at all. It is one of the most important details in a jewellery model.
What a seat is made of
- Size: matched to the stone's girdle, with a small allowance.
- Angle: follows the stone's pavilion, so it sits flat against the metal.
- Depth: places the girdle at the right height, so the prongs can close over it.
- Opening below: a small hole lets light in and helps with cleaning and setting.
Why exact size matters
A tiny difference in size matters on small stones. That is why the stone's exact measurement in millimetres is needed. Stones that are not uniform may need a larger allowance. See calibrated vs freesize stones.
Seats for different stones
Round seats are the simplest. Other shapes need seats shaped to the stone and its corners. See stone shapes.
Check before printing
Print a test of the seat area if possible, and have your setter confirm the fit. Our final model check covers this.
Frequently asked questions
How much allowance should a seat have?
It depends on the stone and the setter, so confirm with your setter. Do not rely on a single standard number.
Why is there a hole under the stone?
It lets light in, helps the setter push the stone out for resetting, and allows cleaning.
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