What Does 10.9 Mean On A Bolt

The marking ‘10.9’ on a bolt indicates its property class per ISO 898-1: the ’10’ stands for a minimum tensile strength of 1000 MPa (actually 1040 MPa) and the ‘9’ means the yield strength is 90% of the tensile strength (minimum 940 MPa). These high-strength bolts are commonly used in automotive and structural applications.

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