2-1/2-4 UNC Thread Specifications
Complete dimensions for 2-1/2-4 UNC (Unified National Coarse) thread per ASME B1.1. TPI: 4, Pitch: 0.25" (6.35 mm).
Thread Dimensions
| Designation | 2-1/2-4 UNC |
| Threads Per Inch (TPI) | 4 |
| Pitch | 0.25" (6.35 mm) |
| Major Diameter | 2.5" (63.5 mm) |
| Pitch Diameter | 2.3376" (59.376 mm) |
| Minor Diameter (External) | 2.1933" (55.709 mm) |
| Minor Diameter (Internal) | 2.2294" (56.626 mm) |
| Thread Depth | 0.13532" (3.437 mm) |
| Tensile Stress Area | 3.99883 in² (2579.9 mm²) |
Tap Drill Size
Recommended tap drill: 2-15/64" (2.2344" / 56.75 mm)
Calculated minor diameter (internal): 2.2294" (56.63 mm)
Proof Loads by SAE Grade
| Grade | Proof Stress (psi) | Tensile Strength (psi) | Proof Load (lbf) | Tensile Load (lbf) |
|---|---|---|---|---|
| Grade 2 | 55,000 | 74,000 | 219,936 | 295,913 |
| Grade 5 | 85,000 | 120,000 | 339,901 | 479,860 |
| Grade 8 | 120,000 | 150,000 | 479,860 | 599,824 |
Common Applications
- Industrial and structural applications
- Coarse thread applications