| 摘要 |
<p>An apparatus makes self-piercing nuts from blanks (11) each having a cylindrical pilot portion (13) which has a raw unopened and unthreaded bore (12) and an end surface serving as a punch. The pilot portion surrounded by a rim (14) extending along a periphery a nut body, and an annular groove (15) is present between the pilot (13) and the rim. The apparatus has a punching die which has a boring punch (33) and a first cylindrical insert (35) fitted on the punch serving to open the bore (12). The boring punch has at its basal portion a tapered annular wall (34), and the cylindrical insert (35) having at its end surface an annular lug (36) capable of fitting in the annular groove. The tapered wall (34) radially expands an end of the pilot portion, so that its peripheral wall is forcibly slanted in a radial direction and an annular edge (13a) of the peripheral wall is stopped by an inner periphery of the annular lug (36). Due to this feature, the apparatus can mass-produce the self-piercing nut of an accurate dimension which can smoothly punch an opening trough a metal plate, and an invariable and sufficient clinching force is ensured to the self-piercing nut. <IMAGE></p> |
