| 摘要 |
PROBLEM TO BE SOLVED: To improve the discharge property of chips by restraining the heat of a face and cutting edge. SOLUTION: A pair of recessed grooves 6, 6 are formed on the head 4 of a ball end mill 20 and the ridge line of the outer periphery side of face 7, 7 which are the surface pointing to the rotation direction are formed to cutting edges 3, 3. The cutting edge 3 is formed in a nearly arc shape from the outer periphery side of the head 4 toward the tip. A coolant hole 22 is provided on respective scoop surfaces 7. A coolant passage 23, 23 communicating respectively to the coolant hole 22, 22 of the head 4 from the base end surface of the shank are drilled in a spiral with a center axis O in it.
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