| 摘要 |
First and second tips 4A and 4B are disposed on the outer periphery of the forward end of an end mill body 1 in a manner such that the tips 4A and 4B are displaced from each other about the periphery of the end mill body 1. The rotation loci of edges of the first and second tips 4A and 4B around the axis O of the end mill body 1 are mutually overlapped. The edge of the first tip 4A protrudes slightly farther toward the forward end of the end mill than the edge of the second tip 4B. Further, third tips 4C are disposed adjacent to the base end of the second tip 4B in such a manner that no gap is formed between the rotation locus of the edge of the third tip 4C located most adjacent to the forward end of the end mill body and the rotation locus of the rear end of the second tip 4B. As a consequence, the second tip 4B and the third tips 4C can be spirally disposed in the rearward rotating direction of the end mill as they extend toward the base end of the end mill. The respective tips 4, moreover, are formed of only one type having the same shape and dimensions. With this construction, the maintenance of tips can be remarkably simplified, and the wear of the tips, in particular, the wear of the first tip 4A, can be inhibited, thereby accomplishing a uniformity of the degree of the wear of the overall tips.
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