| 摘要 |
The head of a screw has a driving formation which has a multilobed profile (7) in a plane perpendicular to the axis of the screw, in which the two sides (8) of each lobe lie at least partially in radial planes, and the sections (10) which join the radially outer ends of pairs of the radial sides (8) lie on a single imaginary conical or pyramidal surface coaxial with the screw. The driving formation can be the inside of a recess or the outside of a projection on the bolt head. The sections (11) joining the radically inner ends of the radial sides (8) lie on the surfaces of a polygonal prism coaxial with the screw x, or on a conial or pyramidal surface. Precise setting of tightening torque by a complementary tool is possible. <IMAGE> |
