| 摘要 |
A fastener for composite material having a dense composition employs a head which has a socket and a recessed underside and a lower rim. The shank has an upper portion with an enlarged diameter and a left hand thread while the lower portion has a tri-lobed configuration and is traversed by a right hand thread. The right hand thread may have a plurality of notches which, in one embodiment, are arranged in a spiral array. |
