ASTM A194 Grade Comparison
Grade 2H Nut
Specification: ASTM A194 Grade 2H
Grade DH Nut
Specification: ASTM A194 Grade 2H with added supplementary requirement S1 OR sometimes referenced as a separate grade
Side-by-Side Comparison
| Feature | Grade 2H | Grade DH |
| Hardness | HRC 24-32 | HRC 24-32 |
| Material | Carbon steel, heat treated | Carbon steel, heat treated |
| Strength | Medium (120 ksi bolts) | Medium (120 ksi bolts) |
| Dimensional Tolerances | Standard | Tighter/Precision |
| Bearing Surface | Standard | Enhanced flatness/perpendicularity |
| Applications | General structural | Precision/Critical applications |
| Cost | Standard | Higher (due to tighter tolerances) |
Important Notes:
- Both have identical hardness ranges – the mechanical strength is the same
- DH is essentially 2H with tighter dimensional control – think of it as “premium 2H”
- Not all manufacturers stock 2H/DH – it may require special order due to the manufacturing requirements
- Galvanizing considerations: Both can be galvanized, but DH nuts must maintain dimensional tolerances even after coating, which requires careful over-tapping
- Inspection requirements: DH nuts typically require more rigorous dimensional inspection and documentation
In Summary:
The main difference is DIMENSIONAL CONTROL – DH nuts have tighter tolerances and more precise manufacturing requirements than 2H nuts, while maintaining the same hardness and strength properties.
