When deciding which fasteners would be best to use for a project, there are several ways to decode their grade. All fasteners come with specific markings to help determine material, make, and grade. Some small size fasteners will not be graded with a specified strength, but larger size fasteners and specialized fasteners are meant to meet specific strength requirements. When replacing a graded fastener, use a replacement the same grade or higher.
Recognizing Bolts By Their Markings
Commonly bolts larger than ¼” are marked on top of their heads. If a bolt is not marked, it is generally a Grade 2. These are typically used for common general fastening. If a bolt contains three lines spaced at 120 degrees apart, it is a Grade 5. These could be used for high-demand, high-strength applications. Bolts with six lines spaced at 60 degrees apart are Grade 8. These are used for high-strength, specialized applications that generally require rigorous control.
Standard Fastener Grades (Top of bolt head)
This chart outlines the common grades of bolts we carry at Global Certified Fasteners.
| Grade Identification Marking | Specification | Fastner Description | Material | Nominal Size Range (in.) | Tensile Strength |
|---|---|---|---|---|---|
No Grade Marking | Grade 1, 2 | Bolts, Screws, Studs | Low or Medium Carbon Steel | ¼ through 1 ½ | 60,000 |
3 Lines, 120° Apart | Grade 5 | Bolts, Screws, Studs | Medium Carbon Steel, Quenched and Tempered | ¼ through 3 | 90,000 – 120,000 |
6 Lines, 60° Apart | Grade 8 | Bolts, Screws | Alloy Steel, Quenched and Tempered | ¼ through 1 ½ | 150,000 |
Common Nuts Markings
Nuts are also coded by grade. On standard nuts, Grade 2 are not marked, but Grades 5 and 8 are using a clock marking system. A dot is located in a corner to indicate 12 o’clock, and a line is placed at the 5 or 8 o’clock positions to identify each grade.
Contact Global Certified Fasteners For All Of Your Fastener Needs
We also offer specialized fasteners to suit a variety of needs. We’re here to answer any and all questions to get the correct products in hand. Please call us at (708)450-9301 to discuss all of our available options.