Connexion BSP / NPT and Common Thread Sizes Guide Parallel Internal and External threads are Fastening Threads and require the use of a gasket or cone seal. Tapered threads are Joining Threads and create a pressure tight seal when used with jointing compound or PTFE tape. Pipe Thread Acronyms | NPT | American Standard Pipe Taper Thread (National Pipe Thread) | FPT | American Standard female Pipe Taper Thread | NPSC | American Standard Straight Coupling Pipe Thread | BSP | British Standard Pipe (can mean either BSPP or BSPT) | BSPP | British Standard Pipe Parallel | BSPT | British Standard Pipe Taper | GHT | Garden Hose Thread | G Thread | British Gas – Parallel (same as BSPP) | R Thread | British Tapered (same as BSPT) |
NPT – National Pipe Thread (US Standard) Nominal Pipe Size (Inches) | Thread per Inch (TPI) | Outside Diameter (Inches) | Outside Diameter (mm) | 1/8” | 27 | 0.405 | 10.3 | ¼” | 18 | 0.540 | 13.7 | 3/8 | 18 | 0.675 | 17.15 | 1/2 | 14 | 0.84 | 17.9 | 3/4 | 14 | 1.05 | 26.67 | 1 | 11.5 | 1.315 | 33.40 | 11/4 | 11.5 | 1.660 | 42.16 | 11/2 | 11.5 | 1.90 | 48.26 | 2 | 11.5 | 2.375 | 60.33 | 21/2 | 8 | 2.875 | 73.03 |
BSP – British Straight and Tapered Nominal Pipe Size (Inches) | Thread per Inch (TPI) | Outside Diameter (Inches) | Outside Diameter (mm) | 1/8” | 28 | 0.402 | 10.21 | ¼” | 19 | 0.531 | 13.49 | 3/8 | 19 | 0.677 | 17.2 | 1/2 | 14 | 0.839 | 21.31 | 3/4 | 14 | 1.059 | 26.90 | 1 | 11 | 1.327 | 33.71 | 11/4 | 11 | 1.669 | 42.39 | 11/2 | 11 | 1.902 | 48.31 | 2 | 11 | 2.374 | 60.30 | 21/2 | 11 | 2.996 | 76.10 |
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