| 摘要 |
PROBLEM TO BE SOLVED: To provide a ball end mill capable of finishing a metal surface beautifully and polished enough to omit or shorten a polishing process as a tail-end process, as well as to prevent chipping by improving nose strength and chip ejecting capability of the ball end mill with using high feed of 0.2 mm per rotation for finishing a curving bottom face and its surroundings to extend a tool life and improve roughness. SOLUTION: In a ball end mill equipped with two blades crossing each other on a nose, the two ball blades are arranged above a center core so that a space 8 between two planes including rake faces of the ball blades can be 1.8 to 3.0% of a radius of the ball blade near the nose, a chisel edge 4 comprised of relieves of the two ball blades is provided so that the chisel angle 5 can be 155 degrees or more, and a ratio of a space between inner edges of the faces of the two ball blades formed in a gash 9 to a chisel edge length is 1 to 7 or 1 to 3.
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