1-3/8-12 UNF Thread Specifications
Complete dimensions for 1-3/8-12 UNF (Unified National Fine) thread per ASME B1.1. TPI: 12, Pitch: 0.08333" (2.117 mm).
Thread Dimensions
| Designation | 1-3/8-12 UNF |
| Threads Per Inch (TPI) | 12 |
| Pitch | 0.08333" (2.117 mm) |
| Major Diameter | 1.375" (34.925 mm) |
| Pitch Diameter | 1.3209" (33.55 mm) |
| Minor Diameter (External) | 1.2728" (32.328 mm) |
| Minor Diameter (Internal) | 1.2848" (32.634 mm) |
| Thread Depth | 0.04511" (1.146 mm) |
| Tensile Stress Area | 1.31471 in² (848.2 mm²) |
Tap Drill Size
Recommended tap drill: 1-9/32" (1.2812" / 32.54 mm)
Calculated minor diameter (internal): 1.2848" (32.63 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 | 72,309 | 97,289 |
| Grade 5 | 85,000 | 120,000 | 111,750 | 157,765 |
| Grade 8 | 120,000 | 150,000 | 157,765 | 197,206 |
Same Size, Different Series
Common Applications
- Heavy structural, foundation bolts, large machinery
- Fine thread applications