1. Both threads (1/2" BSP and 1/2" NPT) are 14 threads per inch (TPI)
2. NPT threads are 60 degree included angle, whereas BSP are 55 degree (i.e. Whitworth form)
3. The easiest way to determine which is which, without a thread gauge, is to try a 1/2" BSP female thread onto both ends of the...