fluted sides, and E is the well known twist drill. The fluted countersink, O, may be classed among the Recent Knglneerlng Inventions. drills; its special application is to form the centers of arti- The drills, G E, are shown in cross section in the central figure. Twist drills of recent manufacture… … ■be easily cleaned. It consists in an are afterward beveled with a file. arrangement of gratings, sluices, This drill is used for boring large LATHE, WITH WOBK SUFFOBT. riflSes, and spiral jets, the construc- holes in sheet metal, a small hole tion and operation of which cannot well be described…
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