How many marks are there on the head of a SAE grade 8 bolt?

The head of a SAE grade 8 bolt is marked with 6 radial lines. These lines are indicative of the strength of the bolt, as grade 8 bolts are designed to have a specific tensile strength and load-carrying capacity. The markings on the head not only serve as a quick visual reference for identifying the bolt grade but also ensure that the right bolt is used for appropriate applications, particularly in critical high-stress environments. Understanding the grading and markings on fasteners is essential for maintenance technicians to ensure safety and reliability in their work.