| 摘要 |
<p>A gun drill having a cutting blade of a single-edged blade in which high cutting efficiency is attained, exact positional accuracy is not required at the time of brazing a cutting blade tip as the cutting blade, a cutting head can be manufactured easily and the cutting blade itself is also easily processed in terms of form is provided. A cutting blade 5 is configured such that an inner end 51a of a blade edge 51 is spaced apart from a head shaft center O to form a non-cutting zone Z in the vicinity of the shaft center O, a cutting blade side face 52 at the inner end 51a side constitutes an inclined surface inclined from the inner end 51a to the head shaft center O side, and a non-cutting core C of a work material W generated in the non-cutting zone Z is broken off by press-contact of the inclined cutting blade side face 52 during cutting processing.</p> |
