| 摘要 |
PROBLEM TO BE SOLVED: To provide a multi-blade ball end mill with a long service life capable of preventing chip clogging. SOLUTION: Thinning is applied to each of ball blades 6a to 6c in a range from backward side in a rotative direction of the ball blades 6a to 6c through to forward side in the rotative direction of the ball blades 6a to 6c. By this thinning, the ball blades 6a to 6c are cut off at and near a rotation center O, and a concave part operating as a chip pocket is formed at and near the rotation center O. In this arrangement that the thinning is applied to each of the blades 6a to 6c, the chip pocket having an enough capacity is secured near the rotation center, which prevents a chipping of the cutting blades caused by the chip clogging during cutting. That the length of the cutting blade of each of the ball blades 6a to 6c can be made to the same length prevents concentration of a cutting load to one particular blade out of the ball blades 6a to 6c. As a result, chipping of all the ball blades 6a to 6c is prevented.
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