| 摘要 |
PURPOSE:To reduce the eccentricity of an outer peripheral flange and the dispersion amount by performing in order the forming of a center flange and the diameter contraction forming of a spare flange to the necessary outer peripherals flange after forming the spare flange in a little larger diameter than the necessary dimension of the outer peripheral flange. CONSTITUTION:The spare flange 49 in the outer diameter D+alpha larger by several mm than the necessary external shape of an outer peripheral flange is formed on the work W completing a drawing on a preforming article. A burring prepared hole 50 at the center part and bolt hole 51 are respectively subjected to a piercing and a dressing hole is pierced at a joggle part. The center flange 53 with the specified inner diameter around the burring prepared hole 50 is subjected to a burring, then, and the spare flange 49 is formed with its diameter contraction on the outer peripheral flange 54 in the necessary outer diameter D with the center flange 53 as the reference as well. Tapered faces 55, 56 are finally subjected to a coining respectively on the center flange 53 and nut seat.
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