| 摘要 |
PROBLEM TO BE SOLVED: To provide a drill for deep hole boring, boring a deep hole having a depth about 15 to 30 times the drill diameter, and discharging chips without a special process such as a step feed. SOLUTION: This twist drill for boring a deep hole includes: a first web thickness part in which the web thickness of a blade part of the drill is substantially uniform extending from the tip side toward the base end side, and a second web thickness part. The thickness of the first web thickness part is set larger than that of the second web thickness part, and the tip angle of the drill has two or more steps. COPYRIGHT: (C)2005,JPO&NCIPI
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