| 摘要 |
The hexagonal head (3) has an essentially spherical configuration being truncated at the mutually opposite cutoff planes (a,b) along the axial centreline (e) of the body of the screw (1), said hexagonal head (3) consisting in a succession of curved faces (5) by way of spherical lunes, said faces being flat when considered in an orthogonal direction with respect to the axial centreline (e) and curved when considered in a longitudinal direction with respect to said centreline (e) between the two meridians (6) delimiting them, said faces having their biggest width in correspondence with the middle plane, their width becoming smaller towards the cutoff planes (a,b), each meridian (6) making up the common curved edge between each pair of the aforementioned faces.
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