1-5/8-18 UNEF Thread Specifications
Complete dimensions for 1-5/8-18 UNEF (Unified National Extra Fine) thread per ASME B1.1. TPI: 18, Pitch: 0.05556" (1.411 mm).
Thread Dimensions
| Designation | 1-5/8-18 UNEF |
| Threads Per Inch (TPI) | 18 |
| Pitch | 0.05556" (1.411 mm) |
| Major Diameter | 1.625" (41.275 mm) |
| Pitch Diameter | 1.5889" (40.358 mm) |
| Minor Diameter (External) | 1.5568" (39.544 mm) |
| Minor Diameter (Internal) | 1.5649" (39.747 mm) |
| Thread Depth | 0.03007" (0.764 mm) |
| Tensile Stress Area | 1.93808 in² (1250.4 mm²) |
Tap Drill Size
Recommended tap drill: 1-9/16" (1.5625" / 39.69 mm)
Calculated minor diameter (internal): 1.5649" (39.75 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 | 106,594 | 143,418 |
| Grade 5 | 85,000 | 120,000 | 164,737 | 232,570 |
| Grade 8 | 120,000 | 150,000 | 232,570 | 290,712 |
Common Applications
- Precision assemblies
- Thin-wall tubing
- Aerospace fittings