2-3/4-4 UNC Thread Specifications
Complete dimensions for 2-3/4-4 UNC (Unified National Coarse) thread per ASME B1.1. TPI: 4, Pitch: 0.25" (6.35 mm).
Thread Dimensions
| Designation | 2-3/4-4 UNC |
| Threads Per Inch (TPI) | 4 |
| Pitch | 0.25" (6.35 mm) |
| Major Diameter | 2.75" (69.85 mm) |
| Pitch Diameter | 2.5876" (65.726 mm) |
| Minor Diameter (External) | 2.4433" (62.059 mm) |
| Minor Diameter (Internal) | 2.4794" (62.976 mm) |
| Thread Depth | 0.13532" (3.437 mm) |
| Tensile Stress Area | 4.93401 in² (3183.2 mm²) |
Tap Drill Size
Recommended tap drill: 2-31/64" (2.4844" / 63.1 mm)
Calculated minor diameter (internal): 2.4794" (62.98 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 | 271,371 | 365,117 |
| Grade 5 | 85,000 | 120,000 | 419,391 | 592,081 |
| Grade 8 | 120,000 | 150,000 | 592,081 | 740,102 |
Common Applications
- Industrial and structural applications
- Coarse thread applications