It is welded, then coated with plastic by fusing the plastic to the metal. On the tripod frame is an adjustable bolt used as a stop to indicate when a facet is done. You set this when you measure your angle with the protractor and index as you work. The index is critical, and he machines that so the index barrel will have either 64 or 96 indexes or degrees of setting. The finer the indexing is, the more accurate you can get your facet angles.
Accurate geometry is absolutely necessary for any faceting operation.
After all, the flash of a gem depends on the facets being at the correct angle to refract and reflect incoming light. The index is attached to a faceter body and the dop slides through these with the gem waxed to it. Being an engineer, Jack decided to try to develop something like this about 20 years ago. He first begged for used laps from friends, simply recharging them as needed. Then he began using copper roof flashing from the hardware store.