Bolt Grade Markings Chart
Head markings identify a bolt strength. This chart covers the common SAE, metric, and stainless designations.
| Grade / class | Head marking | Material | Tensile (psi) |
|---|---|---|---|
| SAE Grade 2 | No marking | Low carbon steel | 74,000 |
| SAE Grade 5 | 3 radial lines | Medium carbon steel, Q&T | 120,000 |
| SAE Grade 8 | 6 radial lines | Alloy steel, Q&T | 150,000 |
| Metric 8.8 | 8.8 | Medium carbon steel, Q&T | 116,000 |
| Metric 10.9 | 10.9 | Alloy steel, Q&T | 151,000 |
| Metric 12.9 | 12.9 | Alloy steel, Q&T | 177,000 |
| Stainless A2-70 | A2-70 | 304 stainless | 101,000 |
Metric: first digit = tensile strength / 100 (MPa); second digit = yield ratio (x 10).
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