3/4-20 UNEF Thread Specifications
Complete dimensions for 3/4-20 UNEF (Unified National Extra Fine) thread per ASME B1.1. TPI: 20, Pitch: 0.05" (1.27 mm).
Thread Dimensions
| Designation | 3/4-20 UNEF |
| Threads Per Inch (TPI) | 20 |
| Pitch | 0.05" (1.27 mm) |
| Major Diameter | 0.75" (19.05 mm) |
| Pitch Diameter | 0.7175" (18.225 mm) |
| Minor Diameter (External) | 0.6887" (17.492 mm) |
| Minor Diameter (Internal) | 0.6959" (17.675 mm) |
| Thread Depth | 0.02706" (0.687 mm) |
| Tensile Stress Area | 0.38626 in² (249.2 mm²) |
Tap Drill Size
Recommended tap drill: 45/64" (0.7031" / 17.86 mm)
Calculated minor diameter (internal): 0.6959" (17.68 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 | 21,244 | 28,583 |
| Grade 5 | 85,000 | 120,000 | 32,832 | 46,351 |
| Grade 8 | 120,000 | 150,000 | 46,351 | 57,939 |
Same Size, Different Series
Common Applications
- Precision assemblies
- Thin-wall tubing
- Aerospace fittings