Bolt Property Classes (Grades)
A bolt's property class (e.g. 8.8) encodes its strength: the first number ×100 is tensile strength (MPa); the product of the two numbers ×10 is yield.
| Class | Tensile (approx.) | Yield (approx.) |
|---|---|---|
| 4.6 | 400 MPa | 240 MPa |
| 5.6 | 500 MPa | 300 MPa |
| 8.8 | 800 MPa | 640 MPa |
| 10.9 | 1000 MPa | 900 MPa |
| 12.9 | 1200 MPa | 1080 MPa |
Grade 8.8 is common in structural connections; HSFG bolts (e.g. 8.8/10.9) transfer load by friction.
Frequently asked questions
- What does bolt grade 8.8 mean?
- Tensile strength ≈ 800 MPa and yield ≈ 640 MPa (0.8 × 800).
Related resources
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