| 摘要 |
PROBLEM TO BE SOLVED: To prevent a stepped cutting edge from cracking and wearing while securing its machining accuracy to improve durability. SOLUTION: A part extending from a step 18 to a large diameter part 16 is ground by a blade, whereby a tilt angleθof the stepped cutting edge 54 is made within a range of 10-25°, and becomes smaller than a torsion angleβof a helical flute 22 so that the cutting edge 54 gets stronger and its breakage is suppressed. In addition, since the tilt angleθcorresponds to an axial rake angle, the cutting edge gets sharper than cases where the edge has a straight edge with a rake angle of 0°or a chamfer is provided. Thus, better machining accuracy can be attained and also abrasion can be suppressed, thereby obtaining better durability by a combination with the mentioned suppression of the breakage. COPYRIGHT: (C)2007,JPO&INPIT
|
