| 摘要 |
<p>Provided is a three-fold symmetric throwaway tip for deep-hole drilling applicable to both a whole cutting type and a non-cutting core break-off type as a center side blade body for a drill head. The throwaway tip for deep-hole drilling is of a thick plate shape having a three-fold symmetry that a sectional shape when divided into three sections P1 to P3 at a central angle of 120 degrees is equalized. The throwaway tip has a blade point 1 facing a drilling direction in a mounting state on a drill head D1, D2 and having an inner cutting blade 11 shorter in blade length and an outer cutting blade 12 longer in blade length forming an angular shape corresponding to a first section P1, and the outer cutting blade 12 is composed of two consecutive cutting blade portions of a peak-side outer cutting blade portion 12a having a smaller outer cutting blade angle ²1 and a foot-side outer cutting blade portion 12b having a larger outer cutting blade angle ²2.</p> |
