In all these cases, no guide whatever is employed for producing the form, the perfection of which depends entirely upon the figure of the edge of the mill, and the dexterity of the workman. Sharp internal angles are not often attempted, as it is difficult to maintain the sharp angle of the grinder.

The minute cutting on the surfaces of small works, such as coral drops for ear-rings, and similar objects, is performed by another class of artizans, who mount small angular, flat, or rounded grinders, upon horizontal spindles in the ordinary lathe, and apply the work beneath the grinders, in much the same manner as the glass-cutters; indeed, the coral cutting may be considered to form a link between glass-cutting, and seal engraving, described respectively in sect. v., chap, xxxiii., and sect. iii., chap. xxxv.

For perforating very small holes through beads and similar objects, the lapidary employs as a drill a small steel or iron wire, such as fig. 67, page 178, Vol. I. The wire is mounted in a chuck, to revolve horizontally upon an ordinary lathe mandrel, and is charged with diamond powder in the same manner as the slicer. For holes more than about the twentieth of an inch diameter, tubular drills are used, such as fig. 71, made of thin sheet iron, bent around a small central wire. These drills remove a small solid core, which breaks when the tube has penetrated some little distance, and the core is pushed out of the tube by passing a fine needle through a hole in the side.

Larger tubes are employed in the same manner for cutting out the circular holes sometimes made in large brooches for the insertion of another stone, or a locket. If the hole is required to be oval, two circular holes of suitable size are made to constitute the two ends of the oval, and the little angular pieces left between the two circles are removed with a small conical grinder. Small tubes are soldered upon the metal wires, but those exceeding about half an inch in diameter are, by the lapidary, generally attached by cement to a wooden chuck. These annular drills are sometimes made as large as from one to two inches diameter, and thus the lapidary's tubular drills are carried up to the size of the smallest circular cutters or grinders used for similar purposes in marble, as alluded to in page 1208 of the present volume.