Definition

The index wheel is, in most usage, a common synonym for the index gear, the toothed wheel mounted on the spindle of a faceting machine that controls the rotational position of the stone during cutting. The terms are used interchangeably across the lapidary trade, with index gear being more common in technical and engineering contexts and index wheel being more common in casual and instructional contexts.

Function and construction

The index wheel functions identically to the index gear: a toothed disk on the spindle, engaged by the index pin to lock the stone's rotational position. Construction is typically machined steel with peripheral teeth, with the number of teeth determining the available angular increments. Common configurations are 64, 80, 96 and 120 teeth.

Some lapidary equipment manufacturers reserve the term index wheel for the visible disk on the operator's side of the machine head, as distinct from the internal gear mechanism. In this usage the index wheel is the user-facing component while the gear is the internal mechanism. This distinction is not consistently observed across manufacturers, and the terms remain effectively synonymous in most trade usage.

In trade context

For the working lapidary, the practical significance of the term is identification of the component on different equipment. Faceting machine documentation, repair manuals and parts lists may use either term. The cutter encountering a reference to either term should understand it as the toothed positioning component on the spindle.