The raised or recessed marks a manufacturer forms into the top of a fastener head during heading. They show the grade, such as radial lines for SAE grades, a class number like 10.9 for metric, or the designation on structural and alloy bolting, plus a manufacturer's identification symbol. A grade mark with no maker's mark is a red flag for counterfeit or non-conforming product.
Head marking shows three lines but no maker's mark, so pull the lot and ask the distributor for the certs.
Also heard as
- head stamp
- grade markings
Related terms
SAE grade
The inch bolt strength system, chiefly Grades 2, 5 and 8, identified by radial lines on the head.
Property class
The metric strength grade of a bolt or nut, stamped on the head as a number such as 8.8, 10.9 or 12.9.
Mill cert
Shop name for the material test report tracing steel back to its mill heat, chemistry and test results.
Cold heading
Forming bolt and screw heads from wire at room temperature by striking it in dies at high production rates.