What do the numbers mean?

The “8.8” you see on a bolt refers to its grade or class, and it provides important information about the bolt’s tensile strength and mechanical properties. In this specific case:

The First Number ‘8’ indicates the ultimate tensile strength of the bolt material, measured in megapascals (MPa). In the case of an 8.8 bolt, the first “8” signifies that the bolt has a tensile strength of 800 MPa. This is a measure of how much force the bolt can withstand before breaking when subjected to a pulling or stretching force.

The Second Number ‘8’ represents the yield strength of the bolt material, also measured in megapascals (MPa). The yield strength is the point at which the bolt will deform permanently under tension. In this case, the yield strength is also 800 MPa.

In summary, an 8.8 bolt is one with a tensile strength of 800 MPa and a yield strength of 800 MPa. The higher the grade or class number, the stronger and more durable the bolt. These grades are standardized to ensure that bolts are used in appropriate applications based on their strength and load-bearing capabilities.