3/8-24 UNF Thread Specifications
Complete dimensions for 3/8-24 UNF (Unified National Fine) thread per ASME B1.1. TPI: 24, Pitch: 0.04167" (1.058 mm).
Thread Dimensions
| Designation | 3/8-24 UNF |
| Threads Per Inch (TPI) | 24 |
| Pitch | 0.04167" (1.058 mm) |
| Major Diameter | 0.375" (9.525 mm) |
| Pitch Diameter | 0.3479" (8.838 mm) |
| Minor Diameter (External) | 0.3239" (8.227 mm) |
| Minor Diameter (Internal) | 0.3299" (8.379 mm) |
| Thread Depth | 0.02255" (0.573 mm) |
| Tensile Stress Area | 0.08783 in² (56.7 mm²) |
Tap Drill Size
Recommended tap drill: 21/64" (0.3281" / 8.33 mm)
Calculated minor diameter (internal): 0.3299" (8.38 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 | 4,831 | 6,499 |
| Grade 5 | 85,000 | 120,000 | 7,466 | 10,540 |
| Grade 8 | 120,000 | 150,000 | 10,540 | 13,174 |
Same Size, Different Series
Common Applications
- Structural brackets, automotive, equipment mounting
- Fine thread applications