| 摘要 |
PROBLEM TO BE SOLVED: To improve chip disposal property by dividing and refining chips. SOLUTION: A gun drill 1 includes a body 2 to be rotated around an axis O, a groove 4 formed to be extended from the distal end toward the rear end side on an outer peripheral part of the body 2, a rake face 5 formed on an inner peripheral surface directed to a drill rotating direction T front side of the groove 4, a distal end flank 7 formed on a distal end surface of the body 2, and a cutting blade 8 formed in an intersecting ridge line part of the distal end flank 7 and the rake face 5. The rake face 5 is divided in the radial direction of the body 2 and is formed into a stepwise shape having at least a step part 6. A rise surface 6a of the step part 6 is inclined to drill rotating direction T rear side and the radial direction inside in relation to a tangential line L of a rotation locus circle drawn by a corner part 6b of the step part 6. COPYRIGHT: (C)2009,JPO&INPIT
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