| 摘要 |
PURPOSE:To make the plate thickness of the cylinder part uniform to contrive to improve the roundness of the inside diameter of the cylinder part by performing the piercing process of a prepared hole for burring after coining of the top surface of the projected cylinder formed by projection processing. CONSTITUTION:After forming a specified prepared hole 22 on a raw plate 20 by means of the piercing process 21, the projected part 24 is formed by projection processing 23 to thin the side wall thickness of the cylinder 25. Then after thinning the thickness of the top plate 26 of the projected cylinder equivalent to that of the side wall of the cylinder 25 the prepared hole 29 for burring is formed by piercing process 28 of the prepared hole for burring and at last the cylinder part is formed by burring process 30 to obtaine the specified inside diameter. Like this, by performing the burring process 30 after equializing the thickness of the top plate 26 and the side wall 25 the thickness of the cylinder part 31 and the distribution of the strain in the side wall part can be made uniform to improve the roundness of the inside diameter of the cylinder.
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