Whitworth Pipe Threads
BSPP (G) - British Standard Pipe Parallel and BSPT (R/Rp) – British Standard Tapered Pipe for pipes and tapered threads - G/R/Rp.
The Whitworth thread specifies a 55° thread angle and a thread depth of 0.640327p and a radius of 0.137329p where p is the pitch.
The most common types of Whitworth pipe threads are
- BSPP (G) – British Standard Pipe Parallel - see ISO 228 Pipe Threads where Pressure-tight Joints are not made on the Threads
- BSPT (R/Rp) – British Standard Tapered Pipe for pipes and tapered threads - see ISO 7 - Pipe Threads where Pressure-tight Joints are made on the Threads
In the UK metric ISO threads have replaced Withworth (BSW) and British Standard Fine (BSF) threads. In USA the most common threads are "Unified Fine" (UNF) and "Unifed Coarse" (UNC).
BSPP (G) – British Standard Pipe Parallel
| Thread size (inch) | Major Diameter (mm) | Minor Diameter (mm) | TPI |
|---|---|---|---|
| G 1/16 | 7.723 | 6.561 | 28 |
| G 1/8 | 9.728 | 8.566 | 28 |
| G 1/4 | 13.157 | 11.445 | 19 |
| G 3/8 | 16.662 | 14.950 | 19 |
| G 1/2 | 20.955 | 18.631 | 14 |
| G 3/4 | 26.441 | 24.117 | 14 |
| G 1 | 33.249 | 30.291 | 11 |
| G 2 | 59.614 | 56.656 | 11 |
- TPI = threads per inch
BSPT (R/Rp) – British Standard Tapered Pipe
| Male Thread size (inch) | Female Thread size (inch) | Major Diameter (mm) | Minor Female Diameter (mm) | TPI |
|---|---|---|---|---|
| R 1/16 | Rp 1/16 | 7.723 | 6.490 | 28 |
| R 1/8 | Rp 1/8 | 9.728 | 8.495 | 28 |
| R 1/4 | Rp 1/4 | 13.157 | 11.341 | 19 |
| R 3/8 | Rp 3/8 | 16.662 | 14.846 | 19 |
| R 1/2 | Rp 1/2 | 20.955 | 18.489 | 14 |
| R 3/4 | Rp 3/4 | 26.441 | 23.975 | 14 |
| R 1 | Rp 1 | 33.249 | 30.111 | 11 |
| R 2 | Rp 2 | 59.614 | 56.476 | 11 |
- BSPT male threads seal against threads of fixed BSPT female.
- BSPT male and BSPP male with conical 30° seat seal against matching conical 30° seat of BSPP female swivel.
