Head of a countersunk screw
The invention relates to the head of a countersunk screw with a lower side which has at least one supporting surface, which forms part of a rotational surface about the screw axis and can nestle against a correspondingly contoured countersunk surface of an add-on part, and has at least one depression which is delimited by a cutting edge at its end which runs downwards, as seen in the screwing-in direction of the countersunk screw. The invention is distinguished in that in front of the supporting surface, as seen in the screwing-in direction, there is an approach surface which butts against said supporting surface, is inclined radially inwards and, at its upwardly running, free end, has the cutting edge which, over its length, maintains a radial distance from the rotational surface to the inside.
1. Head of a countersunk screw with an underside which has at least one support surface edge which support surface edge is part of a rotational surface around the screw axis and can cling to a correspondingly contoured countersunk surface of an add-on part, and at least one depression, which depression is delimited by a cutting edge at its trailing end, as seen in the screwing-in direction of the countersunk screw, characterized in that a radially inwardly inclined advancing surface which abuts the support surface is arranged downstream of the said support surface as seen in the screwing-in direction which advancing surface has the cutting surface at its leading free end, which cutting surface maintains an inward radial distance from the rotational surface over its length.
2. Head according to claim 1 , characterized in that the trailing end of the advancing surface continuously adjoins the support surface.
3. Head according to claim 1 , characterized in that the support surface is part of a conical surface.
4. Head according to claim 1 , characterized in that the support surface is concavely curved.
5. Head according to claim 1 , characterized in that the advancing surface is part of a conical surface.
6. Head according to claim 1 , characterized in that a flank is arranged upstream of the support surface as seen in the screwing-in direction.