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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

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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

Thread size
Major Diameter
Minor Diameter
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
Female Thread size
Major Diameter
Minor Female Diameter
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.
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  • en: G R Rp Whitworth thread BSPP BSPT British standsrd parallel tapered
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