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Marking of fasteners

Hexagon head screws

Kennzeichnung einer Sechkantschraube

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.

Socket head screws

Kennzeichnung einer Zylinderschraube mit Innensechskant

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.

Hexagon nuts

Kennzeichnung einer Sechskantmutter

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).

Studs

Kennzeichnung einer Stiftschraube

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.

Hexagon bolt and nut with left-hand thread

Kennzeichnung von Schrauben und Muttern mit Linksgewinde

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.

Material code

Often, for reasons of space, the finished parts are marked with a material abbreviation:

Kurzzeichen Werkstoffnummer Kurzname
KB 1.5680 X12Ni5
Y* 1.1181 C35E
YK 1.1181 C35E
YB 1.5511 35B2
KG 1.7218 25CrMo4
KA 1.7219 26CrMo4
G 1.7258 24CrMo5
GA 1.7709 21CrMoV5-7
GB 1.7711 40CrMoV4-6
GC 1.7225 42CrMo4
V* 1.4923 X22CrMoV12-1
VH* 1.4923 X22CrMoV12-1
VW 1.4913 X19CrMoNbVN11-1
S 1.4986 X7CrNiMoBNb16-16
SD 1.4980 X6NiCrTiMoVB25-15-2
SB 2.4952 NiCr20TiAl

Y*
V*
VH*

Only for nuts
For 1.4923 with Rp0,2 ³ 600 N/mm²
For 1.4923 with Rp0,2 ³ 700 N/mm²

Sources:
DIN EN ISO 898-1 - Mechanical properties of carbon and alloy steel fasteners - Part 1: Screws with specified strength classes - Standard and fine pitch threads
DIN EN ISO 898-2 - Mechanical properties of carbon and alloy steel fasteners - Part 2: Nuts with specified test loads - Standard threads
DIN EN 3506-1 - Mechanical properties of stainless steel fasteners - Part 1: Screws
DIN EN 3506-2 - Mechanical properties of stainless steel fasteners - Part 2: Nuts
DIN 267-13 - Mechanical fasteners - Technical delivery conditions - Part 13: Parts for bolted joints with special mechanical properties for use at temperatures from -200 °C to +700 °C