| 摘要 |
PROBLEM TO BE SOLVED: To provide a hard carbon coated drill which suppresses heat generation when cutting, improves dischargeability of chips, and dry-drilles even steel or the like for a long time. SOLUTION: The hard carbon coated drill is equipped with at least a pair of helical grooves 11 on a drill body 10, has a first cutting edge 12 formed to be protrusively arcuate from the center of its tip toward the outer periphery and a second cutting edge 13 formed to extend from the first cutting edge toward the outer periphery, and is coated with a hard carbon film 20. The side of a cutting face of the first cutting edge is thinned wherein the rake angleαof the first cutting edge at the thinned region is +3 to +10°; the open angleθof the thinned region is 110°or larger; and the axial distance L from an intersection of the cutting face 14a of the thinned first cutting edge and the helical grooves, and the diameter D of the drill body, satisfy the condition of L/D≥0.2. COPYRIGHT: (C)2005,JPO&NCIPI
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