Bolts (non-metric) and all fasteners are made to meet certain strength requirements and have a grade or ASTM rating. Special markings on screw heads and nuts identify the fastener's grade. Bolts and screws have a grade and manufacturer identification marking. Screws and bolts above 1/4" are typically marked on the top of their head unless Grade 2.
Bolt Grade Markings and Tensile Strength - SAE and ASTM.
- Bolts,Screws,Studs with no tick marks on the head = Grade 2
- Bolts,Screws,Studs with 3 symmetrical tick marks spaced 120° on the head = Grade 5
- Bolts,Screws,Studs with 5 symmetrical tick marks spaced 72° on the head = Grade 7
- Bolts,Screws,Studs with 6 symmetrical tick marks spaced 60° on the head = Grade 8
