1-1/2-18 UNEF Thread Specifications
Complete dimensions for 1-1/2-18 UNEF (Unified National Extra Fine) thread per ASME B1.1. TPI: 18, Pitch: 0.05556" (1.411 mm).
Thread Dimensions
| Designation | 1-1/2-18 UNEF |
| Threads Per Inch (TPI) | 18 |
| Pitch | 0.05556" (1.411 mm) |
| Major Diameter | 1.5" (38.1 mm) |
| Pitch Diameter | 1.4639" (37.183 mm) |
| Minor Diameter (External) | 1.4318" (36.369 mm) |
| Minor Diameter (Internal) | 1.4399" (36.572 mm) |
| Thread Depth | 0.03007" (0.764 mm) |
| Tensile Stress Area | 1.64192 in² (1059.3 mm²) |
Tap Drill Size
Recommended tap drill: 1-7/16" (1.4375" / 36.51 mm)
Calculated minor diameter (internal): 1.4399" (36.57 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 | 90,306 | 121,502 |
| Grade 5 | 85,000 | 120,000 | 139,563 | 197,030 |
| Grade 8 | 120,000 | 150,000 | 197,030 | 246,288 |
Same Size, Different Series
Common Applications
- Precision assemblies
- Thin-wall tubing
- Aerospace fittings