| 摘要 |
<P>PROBLEM TO BE SOLVED: To provide a drill optimized for cutting cast materials, and ensuring low cost in addition to a long service life and excellent cutting performance. <P>SOLUTION: This drill made of hard material includes a principal cutting edge, which is continuously convex in an axial direction starting from the cutting edge. The drill can use the advantages that a cutting angular part is not an acute angle, the main cutting edge is longer, and the load per length of the main cutting edge, especially per unit length within an outer area is reduced. <P>COPYRIGHT: (C)2012,JPO&INPIT |
