Patent ID: 8882411
Filing Date: 2014-11-11
Classification: B23B,H05K,Y10T

Abstract:
1. A drill, comprising: a first cutting edge and a second cutting edge each located at a front end of a cylindrical cutting part; a first flute and a second flute connected to the first cutting edge and the second cutting edge, respectively, the first and second flutes being positioned helically from the front end to a rear end on a peripheral section of the cutting part; and a first land and a second land each extended from the front end to the rear end on the peripheral section of the cutting part, the first and second lands being located between the first flute and the second flute, respectively, wherein the first flute and the second flute are separately extended from the front end to the rear end, the cutting part comprises a first region in which a diameter of an inscribed circle in a cross section perpendicular to a rotation axis of the cutting part increases in a direction away from the front end and toward the rear end, an angle difference between the helix angle θ the angle difference between the helix angle θ