| 摘要 |
<P>PROBLEM TO BE SOLVED: To improve breakage strength by increasing core thickness while securing prescribed cutting chip discharge performance, and to perform stable drilling from the beginning of the working. <P>SOLUTION: Because a bottom part 36 of gash 34 formed when applying thinning is provided with roundness of a radius R in a range of 0.03D to 0.05D, cutting chips are easily curled to improve cutting chip discharge performance. By increasing the core thickness W1 in a range of 0.30D to 0.40D, breakage strength is improved while preventing the clogging of the cutting chips. Because a pair of lands are provided with a second margin 56 at a position where a second margin angle α is in a range of 35-45°, support action by the second margin 56 is obtained immediately after the start of the drilling to stabilize the drilling posture. Accordingly, the practical tool lifetime is obtained in the deep hole drilling drill 10 having a long groove length L. <P>COPYRIGHT: (C)2012,JPO&INPIT |
