An inlay machine is, in lapidary usage, a piece of equipment used for cutting and fitting the small stone segments that make up mosaic inlay jewellery. The category covers a range of equipment from simple precision-grinding wheels with fine grits, through specialised cutting and fitting jigs, to integrated machines that perform multiple operations in sequence. Inlay machines are most commonly encountered in workshops producing stone-mosaic work in the southwestern United States Indigenous tradition (Zuni inlay, Hopi inlay) and in similar mosaic-jewellery traditions in Italy (Florentine and Roman pietra dura) and parts of Asia (Indian thewa and Persian moarraq work).

The inlay process

Stone inlay involves cutting small pieces of contrasting stones (commonly turquoise, coral, jet, mother-of-pearl, lapis lazuli, malachite, sugilite and others) to fit precisely into a metal framework or recessed background. The pieces must be cut to fit the pattern shape, polished on the upper surface, and bonded into the framework with epoxy or another adhesive to produce a flush mosaic surface.

The lapidary equipment used for inlay work typically includes:

• Trim saws: For initial cutting of stone slabs to working size.
• Grinding and shaping equipment: For precise shaping of individual inlay pieces, often using fine-grit diamond wheels at lower speeds than general lapidary work.
• Inlay-specific machines: Some workshops use dedicated equipment with multiple grinding wheels, polishing wheels and fitting tools optimised for the small-scale precision required for inlay work.
• Hand fitting tools: Files, abrasive sticks, polishing tools and similar hand equipment used for final fitting and adjustment.

Workshop equipment

Specialised inlay machines available to the lapidary trade include offerings from manufacturers including Diamond Pacific (the Genie and Pixie series include inlay-suitable configurations), Crystalite, and various smaller manufacturers serving the Native American silversmith and jewellery trade in the American Southwest. The equipment is typically priced in the mid-range of lapidary equipment, from approximately $1,000 to $3,000 for serious workshop-grade machines.

Larger-scale inlay production, particularly in the Italian pietra dura tradition centred on the Opificio delle Pietre Dure in Florence, uses workshop equipment that ranges from traditional hand methods (still in use for fine-art conservation and reproduction work) through to more industrial machinery for larger-scale architectural inlay. The traditional hand methods, using foot-operated bow-saws and fine abrasives, can produce work of extraordinary precision but require substantial training and time investment.

The hand-versus-machine question

Inlay work occupies an interesting position on the hand-versus-machine spectrum. The highest-quality traditional inlay (master-grade Zuni and Hopi work, fine pietra dura) is largely produced by hand or with simple equipment, with the precision coming from the maker's skill rather than from machine capability. Machine equipment supports faster production at consistent quality and is appropriate for commercial production at moderate to high volume. The two approaches coexist in the contemporary trade, with the highest-prestige work generally retaining significant hand involvement.