초록 ▼

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 adja

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.

대표청구항 ▼

A twist drill comprising: a cylindrical body including: an axis of rotation longitudinally therethrough; a forward end which contacts a workpiece; a web thickness of 0.2 D to 0.35 D, D being a diameter of said body; and a spiral flute formed in an outer peripheral surface of said body so as to exten

A twist drill comprising: a cylindrical body including: an axis of rotation longitudinally therethrough; a forward end which contacts a workpiece; a web thickness of 0.2 D to 0.35 D, D being a diameter of said body; and a spiral flute formed in an outer peripheral surface of said body so as to extend spirally along a longitudinal length thereof to said forward end and a land disposed adjacent to said flute, and having a flute-width ratio of 0.5 to 0.9said flute having: a first wall facing in a direction of rotation of said body and a second wall extending from an inner end of said first wall to the outer periphery of said body, said first wall terminating at said forward end in a first cutting lip having a radially outermost end disposed on the outer periphery of said body, said second wall being concavely shaped when viewed from said forward end and formed so that, assuming a first line extending from said outermost end perpendicular to a second line connecting said outermost end and said axis of said body, the maximum distance between said first line and said second wall is set in a range from 0.45 D to 0.65 D.