| 摘要 |
PROBLEM TO BE SOLVED: To improve surface roughness and work accuracy of a cutting finish surface and also extend a life of a ball end mill. SOLUTION: This ball end mill is provided with an outer side circular arc- shaped cutting edge part and an inner side curvature cutting edge part. A trip end P of a ridge line 51a in the outer side circular arc-shaped edge part is positioned in the vicinity of a center axis CL of this ball end mill. A ridge line 52a of the inner side curvature cutting edge part is formed so as to be bent toward the circle center O of the ridge line 51a of the outer side circular arc-shaped cutting edge part from the trip end of its ridge line. The ridge line 52a of the inner side curvature cutting edge part draws a circular arc or curved line, and in a connection point P of the ridge line 52a of the inner side curvature cutting edge part and the ridge line 51a of the outer side circular arc-shaped cutting edge part, a tangent T1 relating to the ridge line 52a of the inner side curvature cutting edge part and a tangent T2 relating to the ridge line 51a of the outer side circular arc-shaped cutting edge part are set to the same tangent.
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