| 摘要 |
A fastener with poygonal rim (40) cooperates with an axially projecting section (24) to define a recess (48) in which sheet material (12) is forced to hold the fastener (10) against rotational and axial movement relative to the sheet material (12). The gripping action between the fastener (10) and the sheet material (12) is improved first, that the sheet material (12) is stretched by a tool (92) which extends through the center of the fastener (10), and second by resiliently compressing the center section (24) of the fastener (10) with the die (34). The center section (24) springs outwardly to decrease the size of the recess (48) and grip the sheet material (12). In addition, the rim (40) is resiliently deflected radially outwardly by the die (34). The holding action between the fastener (10) and the sheet material (12) is increased by providing the recess (48) with identations (84) which project into the rim (40) and center section (24). |
