Pearl drilling unit - permits drilling through bore by part drilling from two sides to prevent flaking-off damage

摘要

The mechanism is intended for drilling a bore through a pearl, either part-way towards its centre (b) for mounting, or to produce a through-bore for stringing. It comprises a base with a fixed drill and a carriage which is slidable on the base towards the drill and has clamps (a), to hold the pearl. An adjustable stop (c) limits the drilling depth. The slide support is rotatable through 180 deg. about the pearl centre (b) so that a through-bore can be produced by drilling from two sides, thus preventing flaking of the pearl surface as the drill breaks through from inside. FL.