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DIN 7991

1986 Edition, January 1986

Complete Document

Hexagon socked countersunk head cap screws

Includes all amendments and changes through Change/Amendment , January 1986

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Superseded By: DIN EN ISO 10642

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Description / Abstract:

Field of application

This standard specifies product grade A hexagon socket countersunk head cap screws with ISO metric screw thread from size M 3 up to and including size M 24.

If, in special cases, the screws are to meet requirements other than those given in this standard, e.g. with regard to property class or material, these shall be selected in accordance with the ar:propriate standard. This also applies to the fine pitch thread conforming to DIN 13 Part 13 required in exceptional cases.

As a consequence of the head geometry and the form of the wrench engagement, the critical cross section of screws covered by this standard is located below the hexagon socket and not in the thread. It is thus recommended that the screws should not be used for the transmission of high axial loads involving prestressing.

If a DIN 911 double offset screwdriver is used to tighten the screws by way of their socket, the torsional strength and the design of the key only permit the application of prestressing loads corresponding to about 80% of the prestressing loads specified for the commonly used property class 8.8 screws .