| 摘要 |
To provide a far more practical drilling tool that is capable of drilling holes having good hole position accuracy and hole wall roughness using a small-diameter drill of 0.4 mm or less. A drilling tool in which helical chip-evacuating flutes (2) are formed in the outer circumference of a tool main body (1), wherein the chip-evacuating flutes (2) have a first helical region (3) with a first helix angle ± 1 and a second helical region (4) with a second helix angle ± 2 greater than the first helix angle ± 1 , being provided on the tool base side of the first helical region (3); the tool main body 1 has a first taper region (6) with a first web taper and a second taper region (7) with a second web taper smaller than the first web taper, being provided on the tool base side of the first taper region (6); and a portion (8) where the first taper region (6) and the second taper region (7) are connected in a row is located more toward the tool base side than the portion (5) where the first helical region (3) and the second helical region (4) are connected in a row.
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