1-1/8-18 UNEF Thread Specifications
Complete dimensions for 1-1/8-18 UNEF (Unified National Extra Fine) thread per ASME B1.1. TPI: 18, Pitch: 0.05556" (1.411 mm).
Thread Dimensions
| Designation | 1-1/8-18 UNEF |
| Threads Per Inch (TPI) | 18 |
| Pitch | 0.05556" (1.411 mm) |
| Major Diameter | 1.125" (28.575 mm) |
| Pitch Diameter | 1.0889" (27.658 mm) |
| Minor Diameter (External) | 1.0568" (26.844 mm) |
| Minor Diameter (Internal) | 1.0649" (27.047 mm) |
| Thread Depth | 0.03007" (0.764 mm) |
| Tensile Stress Area | 0.90067 in² (581.1 mm²) |
Tap Drill Size
Recommended tap drill: 1-5/64" (1.0781" / 27.38 mm)
Calculated minor diameter (internal): 1.0649" (27.05 mm)
Proof Loads by SAE Grade
| Grade | Proof Stress (psi) | Tensile Strength (psi) | Proof Load (lbf) | Tensile Load (lbf) |
|---|---|---|---|---|
| Grade 2 | 33,000 | 60,000 | 29,722 | 54,040 |
| Grade 5 | 74,000 | 105,000 | 66,650 | 94,570 |
| Grade 8 | 120,000 | 150,000 | 108,081 | 135,101 |
Same Size, Different Series
Common Applications
- Precision assemblies
- Thin-wall tubing
- Aerospace fittings