BRITISH STANDARD PIPE PARALLEL (BSPP) THREAD DIMENSIONS



BSPP Thread Dimensions Calculator was developed to show British Standard Pipe Parallel Thread form where pressure-tight joints are not made on the threads. BSPP Thread Dimensions Calculator shows dimensions, tolerances and designation for fastening pipe threads for thread sizes from 1/16 to 6 according to ISO 228 - 1 standard. The thread form follows the British Standard Whitworth thread.

Some important notes from the ISO 228 - 1 standard:

- Both internal and external threads are parallel threads.

- BSPP threads are not suitable joint where pressure-tightness is made on the thread. If assemblies with such threads must be pressure-tight, this should be made by compressing two tightening surfaces outside the threads, and by applying an appropriate seal.

- Threads are normally of the truncated form, with crests truncated to the limits of tolerance. There is an exception to this for internal threads, where they are likely to be assembled with external threads in accordance with ISO 7-1 (Pipe threads where pressure-tight joints are made on the threads — Part 1: Dimensions, tolerances and designation)

- For external threads, two classes of tolerances on the pitch diameter are specified; these are Class A and Class B. The choice between class A and class B depends on the conditions of application.

- The symbol for pipe thread type is G for external and internal threads.

- Designation: Internal thread - Pipe thread ISO 228- G 1/2 , External Thread - Pipe thread 1S0 228- G 1/2 A (For tolerance Class A).

British Standard Pipe Parallel Thread (BSPP)
British Standard Pipe Parallel Thread (BSPP) per ISO 228-1

Calculator:

INPUT PARAMETERS
Parameter Value
Pipe Thread Size

 


RESULTS
Parameter Symbol Value Unit
Pipe Thread Size - --- ---
Threads per inch n ---
Pitch of Thread P --- mm
Basic Height of Thread h ---
Height of Sharp V Thread ---
Major Diameter of Thread D (= d) ---
Pitch Diameter of Thread D2 (= d2) ---
Minor Diameter of Thread D1 (= d1) ---
Internal Pitch Diameter
Lower
Tolerance
TD2 ---
Upper
Tolerance
---
External Pitch Diameter
Lower Tolerance
(Class A)
Td2 ---
Lower Tolerance
(Class B)
---
Upper Tolerance
(Class A / Class B)
---
Internal Minor Diameter Lower
Tolerance
TD1 ---
Upper
Tolerance
---
External Major Diameter Lower
Tolerance
Td ---
Upper
Tolerance
---

Definitions:

BSPP Thread: British Standard Pipe Parallel Thread

BSPT Thread: British Standard Pipe Taper Thread

Reference:

  • ISO 228-1 :2000 Pipe threads where pressure-tight joints are not made on the threads - Part 1: Dimensions, tolerances and designation
  • Oberg, E. , Jones ,F.D. , Horton H.L. , Ryffel H.H., (2016) . Machinery's Handbook . 30th edition.  Industrial Press Inc.
  • Oberg, E. , Jones ,F.D. , Horton H.L. , Ryffel H.H., (2012) . Machinery's Handbook . 29th edition.  Industrial Press Inc.