Working gemstones

A method of bruting a gemstone using a bruting tool, comprising:

• securing the stone to a stone holder for rotation about an axis;
• forming an image of the profile of the stone as seen normal to the axis, on a screen having indicia indicating the position of a girdle to be bruted on the stone;
• forming on the screen an image of a movable member;
• moving a movable member into a position related to the bruted girdle position such that feeding the bruting tool to a corresponding end position during bruting will brute the stone girdle substantially to the girdle position indicated;
• registering said end position;
• bruting the stone with the tool and ceasing the feed of the tool when the tool has reached said end position.

A bruting machine for bruting rotating gemstones using a bruting tool by rotating the gemstone about a gemstone axis and feeding the gemstone relative to the tool in a direction radial to the gemstone axis to thereby provide radial feed and work the gemstone, the machine comprising:

• means for determining the location of a working face of the bruting tool prior to bruting a gemstone;
• means for determining the diameter of a girdle to be bruted on the gemstone;
• means for registering the radial feed required for bruting the gemstone, on the basis of the bruting tool working face location and the bruted girdle diameter;
• and
• means for signalling when, during bruting, said required radial feed is reached.

A machine for bruting a gemstone, comprising:

• means for mounting the stone;
• means for mounting a bruting tool;
• a screen which has indicia indicating the position of a girdle to be bruted on the stone;
• means for forming an image of the profile of the stone, as seen normal to the bruting axis, on the screen, and for forming on the screen an image of a bruting tool;
• means for moving the bruting tool into a position related to the bruted girdle position such that feeding the bruting tool to a corresponding end position during bruting will brute the stone girdle to the girdle position indicated;
• and
• means for registering said end position of the bruting tool.