| 摘要 |
PROBLEM TO BE SOLVED: To provide a rotary cutting tool capable of performing not only planing work but also back facing work making a bearing surface vertical to a rotary shaft with no work of a prepared hole by the single rotary cutting tool. SOLUTION: A bottom cutting edge 27 is formed by two throwaway chips 21, an angleθ3 formed by the bottom cutting edge 27 and a rotary shaft J is 90 degrees, two bottom cutting edges 27t are extended along one plane vertical to the rotary shaft J. One bottom cutting edge 27 is extended to also an opposite side as viewed from a tip end surface side beyond its center. Accordingly, even in the case back facing work is applied with no prepared hole, un- worked part is prevented from being generated in the center of a back facing surface of a workpiece.
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