Tensile Strength

High Strength Steel Bolts usually have an hexagonal head with an ISO strength rating (called property class) stamped on the head. The property classes most often used are 4.8, 5.8, 8.8, 10.9. The number before the point is approximately one-hundredth of the nominal tensile ultimate strength of the bolt in Mpa (Megapascal). The number after the point is10 times the ratio of tensile yield strengthto tensile ultimate strength.

 hex-class_5.8For Example



A property class 5.8 bolt has a nominal (minimum) tensile ultimate strength of 500 Mpa, and a tensile yield strength of 0.8 times tensile ultimate strength or 0.8 X 500 = 400 Mpa

Mpa = The measure of force per unit area equal
to 1 million pascals
Yield Strength = The stress point at which a material
begins to deform plastically (i.e bend)
Ultimate Strength = The maximum stress which a material can withstand
when subjected to tension, compression or shearing.