| 摘要 |
PURPOSE: To provide a sufficient machining accuracy by providing a clearance groove which separates first and second spiral parts rotated reversely to each other and adjacent ends of both by a specified distance in the axial direction of a sleeve member to a herringbone groove. CONSTITUTION: A herringbone groove 11 of a sleeve 1 is formed by providing, for example, a small diameter part 1a reduced in diameter by approx. 2μm in the inner surface of the sleeve 1, providing an annular clearance groove 1b in a specified section of the small diameter part 1a, rotating the sleeve 1 clockwise and counterclockwise alternately while feeding it in the axial direction in the same manner as a conventional example so as to cut the small diameter part 1a of the sleeve 1, and boring the small diameter part. Because there is no risk of damaging a cutter when the herringbone groove is machined, it is not required to use a special high strength alloy for cutters and reduced the speed for machining the groove. Thus machining cost can be reduced remarkably and productivity can be increased larger. |
