| 摘要 |
PROBLEM TO BE SOLVED: To provide a small diameter drill for machining machinable ceramics, having a diameter of 2 mm or less, maintaining sharpness of a tip cutting edge and high hole accuracy of a workpiece and preventing a breakage accident by optimizing the shape and material of the tip cutting edge of the drill and suppressing the progress of wear. SOLUTION: The tip cutting edge of the small diameter drill for drilling a hole with a diameter or 2 mm or less in machinable ceramics, includes a center side cutting edge and a peripheral side cutting edge, and the tip angle of a rotation locus is 120-140°in the center side cutting edge, and 70-100°in the peripheral side cutting edge. The projection length of the peripheral side cutting edge is in a range of 5-30% of the diameter. A helix angle is 25-35°, and the circumferential length of a margin part is in a range of 15-30% of the diameter of the small diameter drill. A space between a preceding margin part connected to a leading edge, and a succeeding margin part connected to a heel, is preferably formed in the cut-off shape of a cylinder part. COPYRIGHT: (C)2011,JPO&INPIT
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