| 摘要 |
PROBLEM TO BE SOLVED: To provide a small diameter drill having coolant holes and a cutting edge diameter of 4.0 mm or less, which small diameter drill can reduce pressure loss at a shank portion due to the small diameter of a fluid supplying through-hole arranged at narrow portions of lands. SOLUTION: The small diameter drill has through-holes inside the drill in the range from the rear end of the shank to the neighborhood of cutting edges in order to supply fluids, such as cutting fluids, cutting mists, or air. The through-holes are formed such that a space for a coolant reservoir having a diameter of 0.4 to 0.7 times as large as the diameter of the shank and a length of 0.01 to 0.8 times as large as the length of the shank is provided inside the shank portion from the end of the shank, and the portions of the through-holes from the coolant reservoir to the cutting edges are formed as helicoids. COPYRIGHT: (C)2006,JPO&NCIPI
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