| 摘要 |
PROBLEM TO BE SOLVED: To maintain good chip disposal performance without causing chip clogging by producing segmented chips. SOLUTION: A subsidiary groove 16 is formed to open to a wall face 15A facing to the front side of a chip disposal groove 15 in a drill rotating direction T and to an outer periphery face 13 of a cutting edge portion 12. A flank is given to a wall face 16B facing to the subsidiary groove 16 on the outer periphery side of a drill body in the drill rotating direction T. A cutting edge 19 consists of a cutting edge inner periphery portion 17 formed on an intersecting ridge portion between a front-end region of the wall face 15A facing to the front side of the chip disposal groove 15 in the drill rotating direction T and a front-end flank 14 and a cutting edge outer periphery portion 18 formed on an intersecting ridge portion between a front-end region of the wall face 16A facing to the front side of the subsidiary groove 16 in the drill rotating direction T and the front-end flank 14. COPYRIGHT: (C)2003,JPO
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