The special shaping and hollowing of bowls, ash trays, ink wells, and similar articles is carried out in much the same way, the stone being pressed against smaller caborundum laps. Polishing is effected by laps which are covered with tripoli powder and oil. This work is also laborious; a certain amount of heat is generated by the friction, and care must be taken not to develop or enlarge cracks within the material.
Drilling is specialized work, and requires much experience and a delicate touch. The drill is set with two specially shaped pieces of black diamond, and considerable skill is necessary to set these correctly so that they are not broken in working. The driller sets his own diamonds, their position varying according to the size of hole required. If the prevailing fashion is for beads or button earrings, the driller has a busy time. A bad driller will break his drill frequently and thus make his work unprofitable. The correct setting of the drill is therefore of the utmost importance.
Two black diamonds, which are very small in size, are selected, and these must be shaped if necessary so that they are triangular and of the same length. Constant examination with a loupe is required before they are considered satisfactory. They are then inserted in a wooden holder which is topped by a piece of lead, the lead being grooved to take the stones. They are hammered in and then tested on glass, and lead above the surface of the diamonds being filed away. Their positions in the holder are such that, when the drill is rotated, the diamonds will cut a very small circle. This circle will be deepened by the rotation of a bow until the material is bored through, the narrow core being thrown out as a powder. Although white diamond is harder than the black, it is not so tough. Fine drills are always set with two small black diamonds; larger drills may have more than two pieces inserted.