| 摘要 |
<P>PROBLEM TO BE SOLVED: To enable eight corner blades to be used at one insert and improve processing accuracy of a crankshaft by allowing the insert to be stably attached to a web blade insert mounting seat of a pin mirror cutter or a pin blade insert mounting seat thereof without requiring so high forming accuracy to the insert and the insert mounting seat. Ž<P>SOLUTION: An outer shape has a parallelogramic flat shape, one pair of circumferential surfaces positioned on mutually opposite sides of four circumferential surfaces arranged around a pair of parallelogramic surfaces 11 are made to be cutting faces 13, and chamfering parts 15 with a convex circular arcuate cross section are formed at the cross ridge line sections of the other pair of the circumferential surfaces 14 and the parallelogramic surfaces 11. Corner blades 16 having a convex circular arcuate shape are formed at the corner parts of the cutting surfaces 13 by making the chamfering parts 15 cross the cutting faces 13, and flat parts 17 are extended over a pair of the cutting faces 13 between the chamfering parts 15 at the other pair of the circumferential surfaces 14. Ž<P>COPYRIGHT: (C)2010,JPO&INPIT Ž
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