A, German bit;
B, twist drill.
(C.) Large auger bits generally are fitted with cross handles, as in Fig. 66, as a bitbrace will not give sufficient leverage to make the bit cut the wood; these are called augers. The form shown is known as a “Ford auger.”
(D.) The German bit (Fig. 67, A) is used for boring small holes for screws and nails, and has entirely supplanted the gimlet of our forefathers, as its action is much more rapid. Its progression in sizes is from ¹⁄₁₆” to ¹²⁄₃₂” by 32ds of an inch; this tool is also called a screw bit.
Fig. 68.
A, extension bit;
B, center bit.
(E.) The twist drill (Fig. 67, B) is a valuable tool; every carpenter should own an assortment of twist drills for use in places where other bits may come in contact with iron. The sizes range from ¹⁄₁₆” to ⅝” by 32ds. The round shank drill may be purchased in any size up to 3”, by 64ths of an inch.
(F.) The extension bit (Fig. 68, A) is a very convenient tool for boring a hole of any size within certain limits, and is at times extremely valuable.
(G.) The center bit (Fig. 68, B) is often used in boring holes through thin material which would be apt to be split if an auger bit were used.
(H.) In filing an auger bit, it should be held as shown in Fig. 69, and a small, fine file used on the inside of the lips and the bottom of the cutters; in no case should the outside of the lips be sharpened, as the size of the bit will be reduced. In filing the cutter, be sure that its under side back of the cutting edge is filed enough to clear the wood after the cutter has entered it.