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.

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 0.45D and 0.65D, wherein D is a diameter of the body.

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 had 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 0.45D and 0.65D, wherein D is a diameter of the body.