wer edge of the tube being serrated. Fitted insidethe The shanks and turned cutting edges of the expanding tube is a cylindrical plug with a central point. On the re- | bits in Fig. 17 pass through a mortise in the head of the : : duced shank of the plug is a spi- tool, and are secured to their… … Countersink. Expanding Auger. American pattern was patented by Shetter, in 1831. (See The cutting lips start at the periphery of the bit, and ex- Fig. 2.) It has a spiral blade around a cylindrical core, and tend towardsthe center in concave lines, till they terminate Among the other uses of augers…
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