3-1/2-4 UNC Thread Specifications
Complete dimensions for 3-1/2-4 UNC thread per ASME B1.1. TPI: 4, Pitch: 0.25" (6.35 mm).
Thread Dimensions
| Designation | 3-1/2-4 UNC |
| Threads Per Inch (TPI) | 4 |
| Pitch | 0.25" (6.35 mm) |
| Major Diameter | 3.5" (88.9 mm) |
| Pitch Diameter | 3.3376" (84.776 mm) |
| Minor Diameter (External) | 3.1933" (81.109 mm) |
| Minor Diameter (Internal) | 3.2294" (82.026 mm) |
| Thread Depth | 0.13532" (3.437 mm) |
| Tensile Stress Area | 8.28254 in² (5343.6 mm²) |
Tap Drill Size
Recommended tap drill: 1/1" (1.0" / 25.4 mm)
Calculated minor diameter (internal): 3.2294" (82.03 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 | 455,540 | 612,908 |
| Grade 5 | 85,000 | 120,000 | 704,016 | 993,905 |
| Grade 8 | 120,000 | 150,000 | 993,905 | 1,242,381 |
Common Applications
- Industrial and structural applications
- Coarse thread applications