1. Origin and Standards:
• BSP Thread: BSP thread, developed based on British standards, is commonly used in the United Kingdom and many other countries. It uses inch units instead of metric measurements for British standards.
• NPT Thread: NPT thread, developed in the United States, is a thread type compliant with American standards. NPT threads use inch units and are widely used in the United States.

2. Thread Geometry:
• BSP Thread: BSP threads have a conical structure with a 55-degree angle. The inner surfaces of these threads are tapered, while the outer surfaces are cylindrical. They are designed to fit together between inner and outer threads.
• NPT Thread: NPT threads have a 60-degree tapered structure. Both the inner and outer surfaces of these threads are tapered, ensuring a tight fit with other NPT threaded parts.

3. Applications:
• BSP Thread: BSP threads are commonly used in applications such as hydraulic and pneumatic systems, water plumbing, gas lines, and are prevalent in European and Asian countries.
• NPT Thread: NPT threads are used in the United States and many American-origin countries. This thread type is preferred for applications like the petroleum and gas industry, water supply, steam lines, among others.

4. Tolerances:
• BSP Thread: BSP threads generally have tighter tolerances and may require more precise assembly.
• NPT Thread: NPT threads can have looser tolerances, making them easier to assemble. 

The choice of which thread type to use depends on the region where the application is located and local standards. Using the wrong thread type can lead to leaks or assembly issues, so selecting the correct thread is essential.