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Straight
NPSH
National Pipe Straight Hose
Shares NPT's pitch and diameter system but is cut straight rather than tapered. Common on hose couplings that seal with an internal washer against the mating face rather than on the thread.
- Standard
- ANSI/ASME B1.20.7
- Flank angle
- 60° included
- Sealing
- A washer or gasket compressed against the mating face -- the straight thread only draws the joint together.
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 →