Fig. 1760. Fig. 1761.
[Figs. 1760] and [1761] represent the German bit, which is used for holes from 1⁄16 inch to 3⁄8 inch in diameter. This, as well as all other bits or augers, have a tapered square by which they are driven with a brace, the notch shown at n being to receive the spring catch of the brace that holds them in place. The cutting edges at a and b are produced by cutting away the metal behind them.
Fig. 1762.
[Fig. 1762] represents the nail bit, which is used for boring across the grain of the wood. Its cutting edge severs the fibre around the walls of the hole, leaving a centre core uncut, which therefore remains in the hole unless the hole is pierced entirely through the material. If used to bore endways or parallel with the direction of the fibre or grain of the wood it wedges itself therein.
The groove of the nail bit extends to the point, as shown by the dotted line in the figure. Nail bits are used in sizes from 1⁄16 to 3⁄8 inch.