BSPT & BSPP Threads

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British Standard Pipe Taper (BSPT) & British Standard Pipe Parallel (BSPP) Threads

BSPT & BSPP THREADS

BSP BRITISH STANDARD PIPE Also known as whitworth 55° thread form
BSPT BRITISH STANDARD PIPE TAPER Thread form as 1722.1, BS 21, ISO 7-1, DIN 3852-2 FORM C (MALE), DIN 3852-2 FORM Z (FEMALE)
BSPP BRITISH STANDARD PIPE PARALLEL Thread form per as 1722.2, ISO 228 (THREAD TYPE), ISO 1179
BSPO BRITISH STANDARD PIPE PARALLEL O-RING Thread form per as 1722.2, ISO 228 (THREAD TYPE), ISO 8434-6, BS 5200
British Standard Pipe (BSP) is a family of technical standards for threads that has been adopted internationally for interconnecting hoses and fittings by mating an external (male) thread with an internal (female) thread. British Standard Pipe threads are similar in function to NPT threads, but are generally not interchangeable.
There are two types of BSP threads:

  • British Standard Pipe Taper (BSPT)
  • British Standard Pipe Parallel (BSPP)

BSPT Pipe Threads can be combined into two types of joints:

1. Jointing Threads: These are pipe threads where pressure-tightness is made through the mating of two threads together. They always use a taper male thread but can have either parallel or taper female threads. (International standards require all female threads to be parallel.)

2. Long Screw threads: These are parallel pipe threads used where a pressure-tight joint is achieved by the compression of a soft material (such as an o-ring seal or a washer) between the end face of the male thread and a socket or nipple face, with the tightening of a back nut.

British Standard Pipe threads are similar in function to NPT threads, but are generally not interchangeable.

BSPT male threads seal against threads of fixed BSPT female.
Contact is made on the flanks of the threads.

Use of a thread sealant is recommended for BSPT male to BSPT female connections.
Measure the BSPT male thread OD and female thread ID at the first full thread near the end of the fitting.

BSPT male and BSPP male with conical 30° seat (60° included angle) seal against matching conical 30° seat of BSPP female swivel.

BSPP O Ring male connector has straight threads and O Ring with metal Retaining Ring. It seals against flat external surface of BSPP female port.
BSPP male, with chamfer to locate Bonded Seal also seals against flat external surface of BSPP female port.

Surface irregularities require a Spot Face to ensure effective sealing. Elbows and tees have Lock Nut to allow orientation of fitting to required direction.

BSPP male and BSPP female flat face swivel require a suitable soft washer between faces to seal. For low working pressure.
BSPT & BSPP SIZE & PITCH DASH SIZE BSPT MALE THREAD OD BSPP MALE THREAD OD BSPT FEMALE THREAD ID BSPP FEMALE THREAD ID
inch-TPI mm inch mm inch mm inch mm inch
1/8 – 28 -02 9,5 0.37 9,6 0.38 8,4 0.33 8,6 0.34
1/4 – 19 -04 12,8 0.50 13,0 0.51 11,2 0.44 11,9 0.47
3/8 – 19 -06 16,3 0.64 16,5 0.65 14,7 0.59 15,2 0.60
1/2 – 14 -08 20,4 0.80 20,8 0.82 18,3 0.72 19,1 0.75
5/8 – 14 -10 22,5 0.89 22,8 0.90 20,6 0.81 20,8 0.82
3/4 – 14 -12 25,9 1.02 26,3 1.04 23,9 0.94 24,6 0.97
1 – 11 -16 32,6 1.28 33,1 1.30 29,7 1.17 30,7 1.21
1.1/4 – 11 -20 41,1 1.62 41,8 1.64 38,6 1.52 39,4 1.55
1.1/2 – 11 -24 47,0 1.85 47,7 1.88 44,5 1.75 45,5 1.79
2 -11 -32 58,6 2.31 59,5 2.34 56,4 2.22 57,4 2.26
2.1/2 – 11 -40 74,1 2.92 75,1 2.95 71,9 2.83 72,6 2.86
3 – 11 -48 86,6 3.41 87,9 3.46 84,6 3.33 85,4 3.36
Thread size refers to the nominal bore of the pipe. Subtract approx. 1/4″ (6mm) from thread diameter measurement for nominal pipe size.

Pitch is Threads Per Inch (TPI). “Gas”, “R” & “G” also refer to BSP. “Male Iron (Pipe)” may be BSP or NPT.

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