| 摘要 |
[Problem] To provide a three-blade drill having cutting edges which do not slip easily and have small cutting resistance. [Solution] Provided is a three-blade drill having three thinning cutting edges, the three-blade drill being characterized in that one or two of the thinning cutting edges pass through a rotational center C of the tip of the cutting edges of the three-blade drill, and the remaining one or two thinning cutting edges do not cover the rotational center C. |
