#4-40 UNC Thread Specifications
Complete dimensions for #4-40 UNC thread per ASME B1.1. TPI: 40, Pitch: 0.025" (0.635 mm).
Thread Dimensions
| Designation | #4-40 UNC |
| Threads Per Inch (TPI) | 40 |
| Pitch | 0.025" (0.635 mm) |
| Major Diameter | 0.112" (2.845 mm) |
| Pitch Diameter | 0.0958" (2.432 mm) |
| Minor Diameter (External) | 0.0813" (2.066 mm) |
| Minor Diameter (Internal) | 0.0849" (2.157 mm) |
| Thread Depth | 0.01353" (0.344 mm) |
| Tensile Stress Area | 0.00591 in² (3.8 mm²) |
Tap Drill Size
Recommended tap drill: #44 (0.086" / 2.18 mm)
Calculated minor diameter (internal): 0.0849" (2.16 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 | 325 | 437 |
| Grade 5 | 85,000 | 120,000 | 502 | 709 |
| Grade 8 | 120,000 | 150,000 | 709 | 886 |
Same Size, Different Series
Common Applications
- Machine screws
- Electrical covers
- Small appliances
- Sheet metal