Fig. 1258.
Fig. 1259.
To rough them out to shape, a gauge or template, such as in [Fig. 1256], is used, being about 1⁄32 inch thick, which envelops about one-sixth of the ball’s circumference. After the ball is roughed out as near as may be to the gauge, the stems may be nicked in, as in [Fig. 1257], and broken off, the remaining bits, a, b, being carefully filed down to the template. The balls are then finished by chucking them in a chuck such as shown in [Fig. 1258],[19] and a narrow band, shown in black in the figure, is scraped, bringing the ball to the proper diameter. The ball is then reversed in the chuck, as in [Fig. 1259], and scraped by hand until the turning marks cross those denoted by the black band. The ball is then reversed, so that the remaining part of the black band that is within the chuck in [Fig. 1259] may be scraped down, and when by successive chuckings of this kind the lightest of scrape marks cross and recross each other when the ball is reversed, it may be finished by the ball cutter, applied as shown in [Fig. 1252], and finally ground to its seat with the red-burnt sand from the foundry, which is better than flour emery or other coarser cutting grinding material.
[19] From The American Machinist.
