BSP threads

Since 1965, British industry has been urged to adopt the ISO (International Organization for Standardization) metric thread as a first-choice thread system, with the ISO inch (unified) thread as the second choice. The British Standard Whitworth (BSW), British Standard Fine (BSF), and British Association (BA) threads would then become obsolete. The British Standard Pipe (BSP) thread is to be retained. The changeover has been extremely slow in taking place, and all these threads are available and still in use. 

Britisches Standard Gewinde British Standard Pipe (BSP) thread/fittings... 

The outlet valves of refillable butane cylinders are different from those of refillable propane cylinders. The valve for propane is a handwheel type, with a female 5/8 in BSP LEFT-HAND thread for a POL metal-to-metal connector. A compatible half-coupling must always be used to ensure a leak-free joint. 

The BSP parallel threads, known as Tastening threads, are designated BSPF, the size referring to the bore size of the pipe on which the thread is cut, e.g. 1 inch BSPF has an outside diameter of 1.309 (Appendix 3). 

Where pressure-tight joints are required, BSP taper threads have to be used. These have the same form and number of threads, but the thread is tapered at 1 in 16. 

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