| 摘要 |
PROBLEM TO BE SOLVED: To provide a through hole opening method capable of preventing chipping of a part of a female serration or a cylindrical surface, or untreated burrs left behind in a through hole 11 when forming the through hole 11, and realizing excellent chamfers 36, 36 and excellent shape accuracy of the female serration or the cylindrical surface. SOLUTION: Both faces of a rotation side flange 10 of a hub 7 are held by a stripper 16 and a lower die 17, and an outer circumferential edge of the rotation side flange 10 is pressed by a tool 29 for constraining the outer circumference of the flange. In this situation, a punch 21 for a prepared hole is pressed downward to form a plurality of prepared holes 14 in the circumferential direction of the rotation side flange 10 through the shearing. Next, chamfers 36, 36 are formed on both opening parts in the axial direction of the prepared holes 14. Further, by press-fitting a punch 21 for plastic deformation into the prepared holes 14, the inner circumferential surface of each prepared hole 14 is plastically deformed to form a female serration or a cylindrical surface on the inner circumferential surface, and the problem is solved thereby. COPYRIGHT: (C)2006,JPO&NCIPI
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