#6-40 UNF Thread Specifications
Complete dimensions for #6-40 UNF (Unified National Fine) thread per ASME B1.1. TPI: 40, Pitch: 0.025" (0.635 mm).
Thread Dimensions
| Designation | #6-40 UNF |
| Threads Per Inch (TPI) | 40 |
| Pitch | 0.025" (0.635 mm) |
| Major Diameter | 0.138" (3.505 mm) |
| Pitch Diameter | 0.1218" (3.093 mm) |
| Minor Diameter (External) | 0.1073" (2.726 mm) |
| Minor Diameter (Internal) | 0.1109" (2.818 mm) |
| Thread Depth | 0.01353" (0.344 mm) |
| Tensile Stress Area | 0.01014 in² (6.5 mm²) |
Tap Drill Size
Recommended tap drill: #34 (0.111" / 2.82 mm)
Calculated minor diameter (internal): 0.1109" (2.82 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 | 558 | 750 |
| Grade 5 | 85,000 | 120,000 | 862 | 1,217 |
| Grade 8 | 120,000 | 150,000 | 1,217 | 1,521 |
Same Size, Different Series
Common Applications
- Electronics
- Instrument screws
- Precision assemblies
- Avionics