| 摘要 |
<P>PROBLEM TO BE SOLVED: To provide the top shape of a punch in which the point angle of the punch of a centering punch device in an Assel mill and the point angle of a reproducing plug are taken as within the same range. Ž<P>SOLUTION: In a clamping device for clamping the nose part of a billet to one side of a table on which the billet is placed and the point punch device for pitting a punch hole at the axial center position in the end face of a billet the nose of which is clamped with a clamping device, in the shape of the point punch of the centering device, the point angle θ of the punch is taken as the same angle range as the point angle β of the R-plug. Further, in the shape of the point punch of the centering device, the point angle θ of the punch and the point angle β of the R-plug are taken as 77-83°. Ž<P>COPYRIGHT: (C)2010,JPO&INPIT Ž
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