4-4 UNC Thread Specifications
Complete dimensions for 4-4 UNC (Unified National Coarse) thread per ASME B1.1. TPI: 4, Pitch: 0.25" (6.35 mm).
Thread Dimensions
| Designation | 4-4 UNC |
| Threads Per Inch (TPI) | 4 |
| Pitch | 0.25" (6.35 mm) |
| Major Diameter | 4" (101.6 mm) |
| Pitch Diameter | 3.8376" (97.476 mm) |
| Minor Diameter (External) | 3.6933" (93.809 mm) |
| Minor Diameter (Internal) | 3.7294" (94.726 mm) |
| Thread Depth | 0.13532" (3.437 mm) |
| Tensile Stress Area | 11.08257 in² (7150.0 mm²) |
Tap Drill Size
Recommended tap drill: 3-47/64" (3.7344" / 94.85 mm)
Calculated minor diameter (internal): 3.7294" (94.73 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 | 609,541 | 820,110 |
| Grade 5 | 85,000 | 120,000 | 942,018 | 1,329,908 |
| Grade 8 | 120,000 | 150,000 | 1,329,908 | 1,662,386 |
Common Applications
- Industrial and structural applications
- Coarse thread applications