Bolt Strength Grade Chart: ISO vs SAE
Overview
Mechanical property comparison between metric and imperial bolt strength grades.
Comparison Table
| Metric Grade (ISO) | Imperial Grade (SAE) | Proof Load (MPa) | Tensile Strength (MPa) |
|---|---|---|---|
| Class 8.8 | Grade 5 | 600 MPa | 800 MPa |
| Class 10.9 | Grade 8 | 830 MPa | 1040 MPa |
| Class 12.9 | N/A | 970 MPa | 1220 MPa |
FAQ
Is Class 8.8 equivalent to Grade 8?
No, Class 8.8 is approximately equivalent to SAE Grade 5. Class 10.9 is the metric equivalent to the high-strength SAE Grade 8.
Source Standard
ISO 898-1 / SAE J429