Grade 8 bolts refer to a specific type of bolts used in applications where high strength and durability are required. Grade 8 bolts are made from hardened and tempered alloy steel, which makes them much stronger than ordinary steel bolts.

The “Grade 8” classification is based on the ASTM (American Society for Testing and Materials) standard, which defines the required mechanical properties for bolts. To be classified as Grade 8, a bolt must have a minimum tensile strength of 150,000 psi (pounds per square inch) and a minimum yield strength of 130,000 psi.

Grade 8 bolts are often used in applications where a large load or stress is applied, such as heavy machinery, construction equipment, transportation vehicles, and steel structures. They are also used in environments where vibrations are common, as their durability makes them resistant to weakening and breaking due to vibrations.

In summary, Grade 8 bolts are a specific type of bolts made from hardened and tempered alloy steel, designed to offer superior strength and durability in applications where a large load or stress is applied.