BSPT

British Standard Pipe Thread

This is VERY important !

The threaded part(s) of plumbing fittings are made to a British Standard Pipe Thread size (BSP).

BSP sizes don’t match up with what you would measure using a ruler, which can obviously cause some confusion.

For example a 3/4 BSP thread actually measures more like 1 Inch with a ruler

A list of 16 thread sizes are defined by the standards, ranging from 1⁄16 to 6. The size was originally based on the inner diameter measured in inches of a steel tube for which the thread was intended. This often causes confusion, as people think the size refers to the outside diameter of the male thread.

Two types of threads are used:

Parallel (straight) threads, British Standard Pipe Parallel thread (BSPP)

Taper threads, British Standard Pipe Taper thread (BSPT)

Just to confuse things, often the T in BSPT refers to Thread and doesn't indicate either Taper or Parallel.

The threadform follows the British Standard Whitworth standard

The table below shows dimensions for male threads.

 

Thread

Threads per inch

Pitch mm

Outside Diameter mm

Outside Diameter inches

1/16″

28

0.907mm

7.723mm

0.304″

1/8″

28

0.907mm

9.728mm

0.383″

1/4″

19

1.337mm

13.157mm

0.518″

3/8″

19

1.337mm

16.662mm

0.656″

1/2″

14

1.814mm

20.995mm

0.825″

5/8″

14

1.814mm

22.991mm

0.902″

3/4″

14

1.814mm

26.441mm

1.041″

1″

11

2.309mm

33.249mm

1.309″

1¼″

11

2.309mm

41.910mm

1.650″

1½″

11

2.309mm

47.803mm

1.882″

2″

11

2.309mm

59.614mm

2.347″

2½″

11

2.309mm

75.184mm

2.96″

3″

11

2.309mm

87.884mm

3.46″

4″

11

2.309mm

113.030mm

4.45″

5″

11

2.309mm

138.430mm

5.45″

6″

11

2.309mm

163.830mm

6.45″

Lots more information available at www.bspt.co.uk



 

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