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Marking of steel bolts ISO 898-1:2013

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Demands for the marking of steel bolts are specified in the standard ISO 898-1:2013 “fasteners made of carbon steel and alloy steel”.The marking system for steel bolts is specified with two figures, e.g. 8.8.

The first figure specifies 1/100 of the nominal tensile strength in N/mm2.In this case 8 x 100 = 800 N/mm2.

The second figure specifies the ratio between the bolt’s nominal proof stress and tensile strength in tenths.By multiplying the figures for the bolt’s tensile strength and proof stress, we arrive at the nominal tensile strength.800 x 0.8 = 640N/mm.

In addition to the figures for tensile strength, the bolt must be marked with the manufacturer’s trademark.
Occasionally it can be seen that the bolt’s thread system is specified with an M for metric system.Marking of the thread system is not mandatory.