BSP Thread – British Standard Pipe Thread
There are two types of BSP threads, BSPP and BSPT. BSPP refers to parallel or straight threads. Meanwhile, BSPT refers to tapered threads. Sometimes BSPP threads are referred to as G threads and BSPT threads as R threads. For both of these threads, the flank angle is 55°.
BSP parallel threads commonly seal via a 30° chamfer on the male thread to a 30° recessed cone inside the female thread (swivel only). If it is a port application an o-ring and a washer or bonded washer are needed to achieve a proper seal for parallel threads. For tapered BSP threads, a seal is acquired via thread wedging with additional support from thread sealant or Teflon tape. It is possible for a male BSPT (tapered) to fit into a female BSPP (parallel), so long as the female thread is fixed and not swivel (this is due to the recessed cone seat).
Please refer to the following steps to identify a BSP thread fitting:
- Check whether the threads are parallel or tapered.
- Using a thread gauge or calipers, count the threads per inch (TPI).
- Using calipers, measure the thread O.D. (male thread) or I.D. (female thread).
- Combine your O.D. or I.D. measurement with the TPI you measured.
- Identify the type of British fitting, it is with the seal or angle sealing surface.