The differences between NPT, PT, BSP, and G threads are as follows:

NPT is a 60-degree tapered pipe thread that belongs to the American standard and is used in North America. National standards can be found in GB/T12716-1991_:W

PT is a 55-degree sealed tapered pipe thread, which belongs to the Wyeth thread family and is mostly used in Europe and Commonwealth countries.

Commonly used in water and gas pipe industry, the taper is 1:16. The national standard can be found in GB/T7306-2000G (BSP), which is a 55-degree non-thread sealing pipe thread and belongs to the Wyeth thread family.

Marked as G stands for cylindrical thread. National standards can be found in GB/T7307-2001.I) ZG is commonly known as pipe cone, that is, the thread is processed by a conical surface. This is the case for general water pipe joints. The national standard is marked as Rc for metric threads. It shows that American and British threads are expressed by the number of threads per inch.

This is the biggest difference between them. Metric threads are 60 degrees equilateral profile, British threads are isosceles 55 degrees profile, and American threads are 60 degrees.