1/2-20 UNF Thread Specifications
Complete dimensions for 1/2-20 UNF (Unified National Fine) thread per ASME B1.1. TPI: 20, Pitch: 0.05" (1.27 mm).
Thread Dimensions
| Designation | 1/2-20 UNF |
| Threads Per Inch (TPI) | 20 |
| Pitch | 0.05" (1.27 mm) |
| Major Diameter | 0.5" (12.7 mm) |
| Pitch Diameter | 0.4675" (11.875 mm) |
| Minor Diameter (External) | 0.4387" (11.142 mm) |
| Minor Diameter (Internal) | 0.4459" (11.325 mm) |
| Thread Depth | 0.02706" (0.687 mm) |
| Tensile Stress Area | 0.15995 in² (103.2 mm²) |
Tap Drill Size
Recommended tap drill: 29/64" (0.4531" / 11.51 mm)
Calculated minor diameter (internal): 0.4459" (11.32 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 | 8,797 | 11,836 |
| Grade 5 | 85,000 | 120,000 | 13,596 | 19,194 |
| Grade 8 | 120,000 | 150,000 | 19,194 | 23,992 |
Same Size, Different Series
Common Applications
- Structural steel, automotive suspension, heavy machinery
- Fine thread applications