| 摘要 |
PROBLEM TO BE SOLVED: To obtain good chip discharging property without sacrificing blade strength at an end mill body tip end side part which is made to cross specifically on an axis of a long blade in a ball end mill where the long blades and short blades are alternately formed.SOLUTION: Even-number of cutting edges 7 where a rotational locus around an axis O forms a hemisphere are formed with an interval in a circumferential direction at a tip end of an end mill body 1 which is rotated around the axis O. Every other cutting edges 7 in the circumferential direction are made to be a long blade 7A which is made to cross the axis O of the tip end of the end mill body 1, residual every other cutting edges 7 in the circumferential direction are made to be a short blade 7B having an inner circumferential end at a position spaced apart from the axis O. A gash 6A of the long blade 7A and a gash 6B of the short blade 7B adjacent to its end mill rotating direction T are made to communicate with each other at an end mill body 1 tip end side. The gash 6A of the long blade 7A is made wider in the circumferential direction than the gash 6B of the short blade 7B. |
