British Standard Pipe Threads

BSP threads are fairly uncommon in the workshop but widely used in the home where most U.K. and European plumbing fittings use these threads. The threads are sized not on diameter but on the nominal bore of the pipe to which they are applied. Just to be really odd a ½" pipe doesn′t necessarily have a ½" bore because wall thickness varies with the pressure rating of the pipe. The table below is for tapered threads which are most often used when fitting say a valve with a female thread to a length of steel pipe. Parallel threads are normally found on fittings like ballcocks or taps.

BSP Threads
BSP Threads
BSP Threads
 

British Standard Pipe Threads (BSP) are used throughout the EU but may no longer be referred to as BSP. The current standard for these threads is BS 21 (taper threads) although this has been generally replaced by BS EN 10226-1. and BS EN ISO 0228-1. BSP-R designates a taper thread and BSP-G designates a parallel thread. The thread is a standard Whitworth form with 55° angle with rounded crests and roots.

Terminology

Mostly applicable to taper thread assemblies:-