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Straight
NPSL
National Pipe Straight Locknut
Threads sized for use with a locknut rather than for sealing, common on electrical conduit hubs and fixture joints that need a mechanical lock across a panel or enclosure wall.
- Standard
- ANSI/ASME B1.20.1
- Flank angle
- 60° included
- Sealing
- None -- secured by a locknut, not by thread interference.
Thread profile
A 60° included flank angle with a flat-truncated crest and root -- the single fastest way to tell a Unified/American pipe thread from the other family by eye.
Cut straight: the pitch diameter is constant along the full thread length, with no taper.
Size chart
| Nominal | TPI | Pitch | Major Ø | Pitch Ø | Minor Ø | Tap drill |
|---|---|---|---|---|---|---|
| 1/16 | 27 | 0.0370" | 0.3125" | 0.2884" | 0.2644" | J (0.2764") |
| 1/8 | 27 | 0.0370" | 0.4050" | 0.3809" | 0.3569" | U (0.3689") |
| 1/4 | 18 | 0.0556" | 0.5400" | 0.5039" | 0.4678" | 31/64" (0.4859") |
| 3/8 | 18 | 0.0556" | 0.6750" | 0.6389" | 0.6028" | 5/8" (0.6209") |
| 1/2 | 14 | 0.0714" | 0.8400" | 0.7936" | 0.7472" | 49/64" (0.7704") |
| 3/4 | 14 | 0.0714" | 1.0500" | 1.0036" | 0.9572" | 63/64" (0.9804") |
| 1 | 11.50 | 0.0870" | 1.3150" | 1.2585" | 1.2020" | 1-15/64" (1.2303") |
| 1-1/4 | 11.50 | 0.0870" | 1.6600" | 1.6035" | 1.5470" | 1-37/64" (1.5753") |
| 1-1/2 | 11.50 | 0.0870" | 1.9000" | 1.8435" | 1.7870" | 1-13/16" (1.8153") |
| 2 | 11.50 | 0.0870" | 2.3750" | 2.3185" | 2.2620" | 2" (2.2903") |
| 2-1/2 | 8 | 0.1250" | 2.8750" | 2.7938" | 2.7126" | 2" (2.7532") |
| 3 | 8 | 0.1250" | 3.5000" | 3.4188" | 3.3376" | 2" (3.3782") |
| 4 | 8 | 0.1250" | 4.5000" | 4.4188" | 4.3376" | 2" (4.3782") |
Tap drill calculator
Calculated live
Tap drillJ0.2764" calculated · J (0.2764") nearest standard
- Pitch
- 0.0370"
- Pitch diameter (basic)
- 0.2884"
- Minor diameter (basic)
- 0.2644"
- Clearance drill (normal)
- 11/32" (0.3438")
Comparing against another standard? Open the universal calculator →