Concave Faceting Machine

 

Concave facets are uniquely three-dimensional. They possess length and width defined in the same way as flat facets, but they also have depth to their shape because the cutting and polishing is performed on diamond-charged round cylinders mounted horizontally on the cutting machine. Faceting in this manner creates concave 'conical' facets that are truly three-dimensional in shape.

 

 

 

This is a close-up picture of the same amethyst now being cut on a concave faceting machine. A rotating cylinder replaces the flat lap.

 

 

Because it is a cylinder, not a flat plate, the left right axis of the cutting tool can be changed. The above picture shows the gauge that is used to control the left right direction.

 

 

The up down axis to the cutting cylinder controlled with the above gauge. Therefore, unlike flat faceting, concave faceting has many more potential complex angles and directions.

The gem designer controls the placement, depth and sharpness of the curved, three dimensional facets through the diameter of the cylinder being used. Indeed, many of the best concave gem designs employ a number of different sized cylinders.. Knowing when, how, and what size cylinder to employ are only a portion of the real artistry, skill and technique and challenge involved in concave gem cutting! Coupled with the far greater demand for hand-to-eye coordination and sensitivity - not to mention the depth of understanding of optics - these are just a few of the reasons that concave gem cutting is an art all to itself.