| 摘要 |
A fastener having a shank with a head at one end and a hardened penetrating portion at the opposite end with a frustoconical exterior wall terminating in a penetrating end. The penetrating portion includes a recess having a transverse wall axially spaced from the penetrating end and at least a portion of the transverse wall extends laterally outwardly of the penetrating end to provide an undercut portion. The fastener is adapted to be driven into a hard material so that the hard material flows into the undercut portions of the fastener without deforming the penetrating portion of the fastener.
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