#12-28 UNF Thread Specifications
Complete dimensions for #12-28 UNF (Unified National Fine) thread per ASME B1.1. TPI: 28, Pitch: 0.03571" (0.907 mm).
Thread Dimensions
| Designation | #12-28 UNF |
| Threads Per Inch (TPI) | 28 |
| Pitch | 0.03571" (0.907 mm) |
| Major Diameter | 0.216" (5.486 mm) |
| Pitch Diameter | 0.1928" (4.897 mm) |
| Minor Diameter (External) | 0.1722" (4.373 mm) |
| Minor Diameter (Internal) | 0.1773" (4.504 mm) |
| Thread Depth | 0.01933" (0.491 mm) |
| Tensile Stress Area | 0.02579 in² (16.6 mm²) |
Tap Drill Size
Recommended tap drill: #16 (0.177" / 4.5 mm)
Calculated minor diameter (internal): 0.1773" (4.5 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 | 1,418 | 1,908 |
| Grade 5 | 85,000 | 120,000 | 2,192 | 3,095 |
| Grade 8 | 120,000 | 150,000 | 3,095 | 3,868 |
Same Size, Different Series
Common Applications
- Electronics
- Instrument screws
- Precision assemblies
- Avionics