Importance

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Abstract

A twist drill includes a cylindrical body having an axis of rotation therethrough and having a forward end which contacts a workpiece. The body has a spiral flute formed in an outer peripheral surface thereof so as to extend spirally along a length thereof to the forward end and a land disposed adjacent to the flute. The flute has a first wall facing in the direction of rotation of the body and a second wall extending from an inner end of the first wall to the outer periphery of the body. The first wall terminates at the forward end in a first cutting lip having a radially outermost end disposed on the outer periphery of the body. The second wall is concavely shaped when viewed from the forward end and formed so that, assuming a first line extending from the outermost end perpendicular to a second line which connects the outermost end and the axis of the body, the maximum distance between the first line and the second wall is set to range between 0.45 D and 0.65 D, wherein D is a diameter of the body.

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First Claim