When I was a kid I was fascinated by the incredibly complex multi-layered Chinese ivory balls in which the concentric spheres could rotate independently (attached is one from the Peabody Essex Museum in Salem - which is always full of lovely surprises). I used to wonder how they were made, and then quite recently I came across the best description of the process that I've seen. It's from the Rev. William Milne's 1857 book Life in China:

“A piece of ivory, made perfectly round, has several conical holes worked into it, so that [they] meet at the centre of the globular mass. The workman then commences to detach the innermost sphere of all. This is done by inserting a tool into each hole, with a point bent and very sharp. That instrument is so arranged as to cut away or scrape the ivory through each hole, at equi-distances from the surface. The implement works away at the bottom of each conical hole successively, until the incisions meet. In this way, the innermost ball is separated; and to smooth, carve and ornament it, its various faces are, one after the other, brought opposite one of the largest holes. The other balls, larger as they near the outer surface, are each cut, wrought and polished precisely in the same manner. The outermost ball of course is done last of all.”

I've only ever seen a couple of these multi-layer spheres reduced in size and designed specifically as beads, years ago in a private Hong Kong collection.

Cheers,

Will