A cheater — also called an angle cheater or fine adjust — is a vernier or micro-adjustment mechanism mounted on the mast of a faceting machine that permits the cutter to alter the cutting angle in very small increments, typically 0.1° or finer, without disturbing the primary angle scale setting. It is standard equipment on precision faceting heads and is regarded as indispensable by professional lapidaries and competitive faceters who must achieve exact meet-points across a stone's facet layout.

Function and Mechanism

On any faceting machine the mast carries the quill — the rotating spindle that holds the dopstick and stone — and the primary angle scale sets the gross cutting angle, commonly graduated in whole or half degrees. The cheater is a secondary, finer control, usually a threaded collar, eccentric cam, or vernier slide, that introduces a small angular offset above or below the primary setting. When a cutter discovers that a series of facets meets slightly high or low at a junction, resetting the primary scale would be a coarse and often counterproductive correction; the cheater instead allows a precise nudge of a fraction of a degree, bringing the meet-point into exact alignment without altering the overall geometry of the design.

The adjustment range of a cheater is intentionally narrow — commonly ±1° to ±2° from the primary setting — because its purpose is refinement rather than gross repositioning. Some faceting heads incorporate a graduated dial or numbered scale on the cheater itself, allowing the cutter to record and reproduce a specific offset; others are friction-set and require the cutter to rely on visual inspection of the meet-point under magnification.

Role in Meet-Point Faceting

Meet-point faceting — the discipline of cutting each facet so that its edges terminate precisely at the junctions defined by adjacent facets — demands angular repeatability that the primary scale alone cannot always guarantee. Small variations in dop alignment, stone seating, or lap wear can shift the effective cutting angle by a fraction of a degree. The cheater compensates for these accumulated tolerances in real time. The United States Faceters Guild references the cheater in its instructional materials on advanced meet-point correction, reflecting its established role in competitive and precision amateur cutting as well as professional production.

Relationship to the Index and Mast

The cheater operates in concert with the index gear — the circular plate of equally spaced stops that controls the rotational position of the stone — and the mast, which provides the structural column along which the quill travels. Whereas the index governs which facet is being cut by fixing the stone's rotational position, and the mast angle scale governs the gross cutting angle, the cheater governs the fine angular value at which the lap meets the stone. Together, these three controls — index, primary angle, and cheater — constitute the fundamental geometry-setting system of a precision faceting head.

In the Trade and Among Competitive Faceters

Faceting machines intended for serious use — including those produced by manufacturers such as Graves, Facetron, and Ultratec — incorporate a cheater as a standard feature of the mast assembly. In competitive faceting, where judging criteria include the precision of meet-points and the optical symmetry of the finished stone, the ability to apply a controlled fractional-degree correction can determine whether a stone places or is eliminated. For production cutters working in coloured gemstones, the cheater similarly allows efficient correction of cumulative error without the time cost of a full re-setup.