| 摘要 |
A flat strip of metal moving lengthwise first has its edges turned up by roll-forming. Thereafter it moves into the large end of a horn and along one side of the horn so that that side gradually imposes an increasing curvature on the metal and at the exit end of the horn the metal is substantially cylindrical. A non-galling surface is used on the contact face of the horn. A pin between the edges of the sheet at the exit end of the horn orients the cylindrical tube.
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