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Whitworth Pipe Threads

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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

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

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

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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Related Topics


Thread data - metric, unified, ACME and others.

Related Documents

ANSI B1.20.1 - NPT - American National Standard Taper Pipe Threads

NPT and NPTF pipe threads - dimensions according ANSI/ASME B1.20.1/3.

British Standard Brass Threads

British Brass Thread is an imperial unit based screw thread.

British Standard Cycle Threads

British Standard Cycle is a British Imperial screw thread standard.

BS 21 - Pressure Tight Pipe Thread Joints

BSPT - British Standard Pipe Taper threads & BSP or BSPF - British Standard Pipe Parallel (Straight) threads.

EN 10226 - Pipe Threads where pressure tight joints are made on the threads - Dimensions

Pipe threads where pressure tight joints are made on the threads - Part 1: Taper external threads and parallel internal threads.

ISO 228 - Pipe Threads where Pressure Tight Joints are not made on the Threads

Requirements for thread form, dimensions, tolerances and designation for fastening pipe threads, thread sizes.

ISO 7 - Pipe Threads where Pressure-tight Joints are made on the Threads

Pressure-tight joints made on the pipe threads.

ISO 724 - Metric Threads

Dimensions of metric threads according ISO 724.

Piping Thread Standards

Applied threaded standards used for piping connections.

Threads commonly used in Piping

Piping thread standards.

UNC and UNF - Unified Coarce and Unified Fine Inch Threads

ANSI/ASME B1.1 Unified National Thread - UNC Coarse series and UNF Fine series.

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