Three-quarter inch (3/4 inch) threads are typically calibrated to pipe or machine thread standards. The most common pipe thread standards are BSP (British Standard Pipe Thread) and NPT (American National Pipe Thread) .
1. Technical characteristics of the 3/4-inch BSP pipe thread ( gas pipe thread – G or BSPP)
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Outer diameter: approx. 26.44 mm
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Pitch: 1.814 mm (equivalent to 14 teeth per inch – TPI )
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Thread winding angle: 55 degrees
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Application area: Water, gas, air and hydraulic connections.
2. Specifications for 3/4-inch NPT pipe threads (American standard)
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Outer diameter : approx. 26.99 mm
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Pitch: 14 teeth per inch (TPI)
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Thread winding angle : 60 degrees
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Type: Conical, for better sealing
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Areas of application: Oil and gas industry and energy supply companies
3. Quick comparison
| Special feature | 3/4 inch BSP | 3/4 inch NPT |
|---|---|---|
| OD | 26.44 mm | 26.99 mm |
| Step (TPI) | 14 | 14 |
| Thread angle | 55 degrees | 60 degrees |
| Man | Parallel (BSPP) or conical (BSPT) | Spitz (NPT) |
Note: BSP and NPT threads are not compatible because their angles, shapes, and sealing systems differ.