British Standard Pipe - BSP

BSP: British Standard Pipe

BSP pipe, Like American National pipe (NPT, NPSM), is designated by trade size, rather than actual diameter, which is approximately equal to the thread's Major Diameter in the table below.

There are two types of BSP threads:

  • BSPT: British Standard Pipe Taper -also known as "R" or "Rc" threads
  • BSPP: British Standard Pipe Parallel -also known as "G" or "Rp" threads

Both styles have the same thread angle, shape, and pitch (threads per inch).  However, BSPT threads are tapered and BSPP threads are straight (parallel).  BSP threads have a 55° included angle and have rounded peaks and valleys (this is a Whitworth thread form).

Here are the actual thread dimension data for BSPP and BSPT threads.  The major diameter is a bit larger smaller than the actual OD of the pipe, and the minor diameter should be very close to what you would measure inside the female threaded end of a fitting.  Note that the Gage Length dimension pertains only to the BSPT (tapered) thread. 

 
Pipe Size
Pitch  (Threads/Inch)
NPT/NPS
BSP
 1/16"
27
---
 1/8"
27
28
 1/4"
18
19
 3/8"
18
19
 1/2"
14
14
 5/8"
---
14

 
Pipe Size
Pitch  (Threads/Inch)
NPT/NPS
BSP
 3/4"
14
14
1"
11 1/2
11
1 1/4"
11 1/2
11
1 1/2"
11 1/2
11
2"
11 1/2
11
2 1/2"
8
11

 
Pipe Size
Pitch  (Threads/Inch)
NPT/NPS
BSP
3"
8
11
3 1/2"
8
11
4"
8
11
5"
8
11
6"
8
11
8"
8
---