| 摘要 |
A one way threaded security fastener comprises a head (2, 64) with a socket (3) containing one or more deformable or detachable torque transfer elements (5, 60) which engage a tool (Fig.3, Fig.7, Fig.8) such as a screwdriver during installation and deform or shear off at a predetermined torque leaving the socket with a generally smooth inner wall (6, 62). Preferably the socket (3) is at least partially frustoconical or hemispheroidal with a circular cross section. The torque transfer elements (5, 60) may be made from metal or plastics material, and may be integral with the fastener or may be attached to the socket (3) by glue or the like. An installation tool (Fig.3, Fig.7, Fig.8) is disclosed for use with the fastener. <IMAGE>
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