1-5/16-18 UNEF Thread Specifications
Complete dimensions for 1-5/16-18 UNEF (Unified National Extra Fine) thread per ASME B1.1. TPI: 18, Pitch: 0.05556" (1.411 mm).
Thread Dimensions
| Designation | 1-5/16-18 UNEF |
| Threads Per Inch (TPI) | 18 |
| Pitch | 0.05556" (1.411 mm) |
| Major Diameter | 1.3125" (33.337 mm) |
| Pitch Diameter | 1.2764" (32.421 mm) |
| Minor Diameter (External) | 1.2443" (31.606 mm) |
| Minor Diameter (Internal) | 1.2524" (31.81 mm) |
| Thread Depth | 0.03007" (0.764 mm) |
| Tensile Stress Area | 1.24368 in² (802.4 mm²) |
Tap Drill Size
Recommended tap drill: 1-1/4" (1.25" / 31.75 mm)
Calculated minor diameter (internal): 1.2524" (31.81 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 | 68,402 | 92,032 |
| Grade 5 | 85,000 | 120,000 | 105,713 | 149,242 |
| Grade 8 | 120,000 | 150,000 | 149,242 | 186,552 |
Common Applications
- Precision assemblies
- Thin-wall tubing
- Aerospace fittings