| 摘要 |
The invention relates to a recessed head screw comprising a head (1), a shan k (2) and a thread (3) which extends at least partly on said shank (2). The he ad (1) has a bearing surface (4) which narrows in the direction of the shank (2 ) and a basic contour (5) whose surfaces in a first head section (5a), facing away from the shank (2), converge at a first angle (.alpha.) and in a second head section (5b), facing the shank (2), converge at a second, smaller, angl e (.beta.). To avoid, for example, undesirable deformation, splintering, teari ng or such like, the invention provides for friction ribs (6) to be positioned in the area of the bearing surface (4), which ribs extend over both head sectio ns (5a, 5b) and whose outer edges (K) follow the converging basic contour (5) o f the head (1), so that in each case the first edge area (6a) of the outer edg e (K) of the friction ribs (6) situated in the area of the first head section (5a) and a second edge area (6b) of the outer edge (K) of the friction ribs (6) situated in the area of the second head section (5b) form an obtuse angl e (.gamma.). The bearing surface (4) recedes radially in relation to the converging basic contour (5) of the head (1), in the direction of the shank (2).
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