There are a few different thread types out there. They are not necessarily interchangeable, and some uses two different names.

The most common thread standards are:

  • BSP - British Standard Pipe

  • NPT - National Pipe Thread

  • M - Metric threads

BSP exists in two types, BSPP and BSPT. The last letter indicates the shape of the threads.

  • BSPP - Parallel

  • BSPT - Tapered

Sometimes different names are used for the same thread type. As an example, a 1/2" BSPP can be sold as G1/2". Similarly a 1/2" BSPT can be sold as R1/2".

The picture below illustrates all of this. As you can see, a BSPT male thread will mate with both a BSPP and BSPT female thread.

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