| 摘要 |
PROBLEM TO BE SOLVED: To provide a high-performance end mill preventing the occurrence of a burn-in phenomenon by suitably discharging produced chips to the outside of a hole even if a chips discharging groove get into the hole during cutting machining. SOLUTION: This end mill 1 comprises an arc-shaped first cutting edge portion 2 formed at one end portion in a longitudinal direction, a second cutting edge portion 3 continuously arranged with the first cutting edge portion 2 and spirally formed on a columnar outer peripheral surface, a first chips discharging groove 4 of a specified depth adjacently formed to the second cutting edge portion 3, and a columnar shank portion 5 formed between the first chips discharging groove 4 and the other end portion 5 in the longitudinal direction. A shank portion 6 is provided with a second chips discharging groove 7 of a specified length formed to be continuously arranged with the first chips discharging groove 4, and the depth of the second chips discharging groove 7 is formed to be shallower than that of the first chips discharging groove.
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