| 摘要 |
PROBLEM TO BE SOLVED: To improve a following shift working efficiency by cutting off a predetermined machining margin at a work starting portion for cutting-off working without generating any inconvenience such as a chatting. SOLUTION: When a predetermined machining margin S is cut off from a work starting portion A of a work piece W by moving a rotating tool which has a plurality of cutting edges at its distal end in a axial direction, an arcuate contact angleθ2, at which angle two or more cutting blades do not contact to the work piece W at the same time, is set. Depending on the work contact angleθ2, the center of the tool is sequencialy arranged at first and second positions 1 and 2, each of which is shifted from a cutting center line C by a predetermined distance (p), and a third position 3 located on the cutting center line to act cutting-off work. By repeating the working procedure, the predetermined machining margin S is cut.
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