The down light was developed to aid in determining when the holder arm tab is resting on the angle stop of the Graves Faceting Machine, thus achieving the set angle. The rounded edges of the cast aluminum parts makes it difficult to see the contact and the tried and true method of listening for the sound is difficult in the classroom where 4 or 5 students are cutting at the same time. The signal that indicates a contact between the two surfaces is the lighting of the bulb.

There are three situations where the achievement of the correct angle is critical. These are during the cutting of the main and break facets, the cutting and polishing of the table and the polishing of facets on unsymmetrical stones.

1. Cutting Main and Break Facets – The proper angle is achieved only when the arm tab touches the angle stop. The down light kit is set to light the bulb when the two blocks make contact.
2. Cutting and Polishing the Table – The table is cut to fit the main facets of the crown and although it is near 90 degrees it will be slightly off. The depth and the cheater are adjusted to make the best fit to the mains. Once the best fit is achieved the contact is set so the bulb will light when this angle is achieved. The table will maintain its relationship to the mains, by lowering the stone a few clicks and cutting until the bulb lights. This setting is also used to reset the depth after changing to a polishing lap.
3. Polishing Unsymmetrical Stones – The polishing of unsymmetrical stones requires resetting of the depth for each set of facets even though the angle does not change. This entails the raising and/or lowering of the stone, until the stone just touches the polishing lap. The stone then must be lowered to set the stone flat on the polishing lap. This requires a trial and error procedure to achieve the proper depth. In most cases the down light can eliminate the trial and error by setting the bulb to light when the first facet of a series is flat on the polishing lap.

1. OPERATION OF DOWN LIGHT