Marking of fasteners

The marking of hexagon head bolts with manufacturer's mark and strength classes is mandatory for all strength classes and a nominal thread diameter of d ≥ 5 mm.

The marking of hexagon socket head cap screws with manufacturer's mark and strength classes is mandatory for strength classes ≥ 8.8 and a thread diameter of d ≥ 5 mm. The marking of the screw is to be applied where the shape of the screw allows it.

The marking of hexagon nuts with manufacturer's mark and strength classes is mandatory for all strength classes and with a thread of ≥ M5. The hexagon nuts must be marked recessed on the bearing surface or a wrench flat or raised on the chamfer. Raised markings shall not extend beyond the bearing surface of the nut. As an alternative to marking by means of the strength class code, marking can also be carried out using the clockwise system (see also DIN EN ISO 898 Part 2).

Stud bolts shall be marked with the manufacturer's mark and with the mark of the strength class or the alternative mark. The marking is mandatory for stud bolts of property classes 5.6 to 12.9 with a nominal thread diameter d ≥ 5 mm. The marking shall be applied to the thread-free part of the stud bolt. If marking is not possible there, marking with the strength class shall be applied to the short threaded end (nut end). The manufacturer's mark may then be omitted. The last procedure applies in particular to stud bolts with a tight-fit thread.

Bolts with left-hand thread and nominal thread diameter d ≥ 5 mm must be marked with an arrow indicating the direction of rotation either on the surface of the head or on the crest of the thread end. Hexagon bolts or nuts with left-hand thread may optionally also be marked with a circumferential notch.