| 摘要 |
PURPOSE:To enable air vent holes to be easily machined from the bore side of a sleeve by extending the extension lines to the sleeve bore side of the air vent holes outward through more bore side than the circumferential edge of a cylindrical hole. CONSTITUTION:In one side air vent hole 17, the extension line to the sleeve bore side of longitudinal center line O1-O1 extends outward obliquely through more bore side than the bore surface edge of axially upper end surface side of a sleeve 10. In addition, in the other side air vent hole 18, the extension line to the sleeve bore side, of longitudinal center line O2-O2 extends outward obliquely through more bore side than the bore surface edge of axially lower end surface side of the sleeve 10. Accordingly, the air vent holes can be easily mechined from the bore side of the sleeve.
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