by Duncan Miller

A few months ago I bought an Imahashi faceting machine, Faceting Unit Model FAC-8C, the earlier of two models. This one dates from 1970, co-incident with when I started faceting. Sometime during the 1970s my father owned one briefly, but I took no notice of it then. Now it intrigued me, because it is a platform machine, unlike the more familiar mast machines. Platform machines have several attractive features. You can lift the entire handpiece free of the machine to inspect the stone, and the smaller quill assembly is more stable when cutting low angle crown facets. This model Imahashi also has an ingenious system of replaceable cams that allow you to preform ovals, marquise and pear-shaped stones to specific length/width ratios. Not only that, but the mechanical cam system enables you to set the angle for any one tier of facets, say the crown mains, only once; then as you work your way around the index settings the angles are adjusted automatically for the rest of the facets of that tier. This facilitates and speeds up the production of standardised brilliant cuts in these low-symmetry shapes. So far I haven’t used the cam system, but cut a standard round brilliant in smoky quartz, just to get a feel for the machine. This model Imahashi doesn’t have a cheater and the dops are not keyed, so alignment after transfer and polishing can be tricky.

A later model, FAC-8P, doesn’t have the cam assembly, but it does have a cheater. This was developed in response to requirements of professional cutters who wanted greater flexibility in the indexing, especially for re-cutting gemstones. Justin Prim has documented the history of these developments and how they revolutionised gem cutting in Sri Lanka ( ... 94a5a504c3). Justin is a faceting historian and has described the operation of various other faceting machines in his World of Faceting Machines YouTube videos:

Imahashi faceting machine FAC-8C

Head of the Imahashi machine with the stainless steel cam system to cut an oval

Imahashi handpiece sitting on the platform

Smoky quartz, 15 mm, cut on my ‘new’ machine