Skip to content
Home » Knowledge » What is NPT and BSP Thread

What is NPT and BSP Thread

What is NPT, BSP, G, PT, ZG Thread

As a stainless steel fittings supplier, we have often been asked by our customers: what is the differences between BSP (British Standard Parallel) and NPT (National Pipe Thread)? Next, we will explain their differences.

hex nipplie with BSPT thread

Hex Nipplie with BSPT Thread

What is NPT, BSP, G, PT, ZG Thread

a) NPT, short for American National Pipe Thread, belongs to American standard for sixty-degree taper pipe thread. This standard now is applied in North America. And its corresponding standard can be referred to GB/T12716-1991: W.

b) PT belongs to Japanese standard for taper pipe thread, which is one of Wyeth thread families, and its tooth angle is 55 degrees. This thread is often used in Europe and commonwealth countries, and applied in water and gas pipes and other industries. It is regulated that the taper shall be 1 to 16. Its corresponding standard can be referred to GB/T7306-2000.

c) G is Chinese National standard thread type, and it is a non-thread sealing pipe thread of 55 degrees, which belongs to Wyeth thread family. For the mark G, it represents the cylindrical thread. This national standard can be referred to GB/T7307-2001. Besides, 1/4, 1/2 and 1/8 refer to the size of the thread, and the unit of size is Inch. For people who familiar with this industry, they will say one inch is equivalent to 8 fen (Chinese Unit), and 1/4 inch is equivalent to 2 fen.

d) BSP stands for the Standard of British Parallel Tread. It refers to the cylindrical pipe thread of general British sealing thread (R), which is also one type of Wyeth thread families. For this type, it usually uses cylindrical female thread (known as PS in old standard) and taper male thread (known as PT in old standard) to achieve its sealing purpose.

e) ZG, commonly known as pipe cone, is processed by a cone on its thread surface. Normally, it is applied into the water connections. For its national mark, it is represented by Rc, and its metric thread is shown by pitch. However, for American or British thread, they usually numbers to show the threads. And this is the biggest difference between them. Metric thread is 60° equilateral tooth type, British thread is 55° isosceles tooth type, and American thread is 60°.

NPT thread chart

What is the difference between BSP and NPT thread ?

BSP belongs to British pipe thread, and it can be divided into BSP. Tr., BSP. PI., and BSP. PF..

BSP. Tr., known as BSPT, is a conical pipe thread. And its thread angle is 55° with the taper being 1 to 16 for sealing joint.

BSP. PI. Is parallel pipe thread. It is like Chinese 55° cylindrical (parallel) pipe threads (G-type). This one only has female threads for sealing, it can be fitted with the male thread of BSPT.

BSP. F. is parallel thread, and normally used for general connections.

Undoubtedly, knowing BSP is not enough at all. It is also important to do the detailed confirmation. Or it will bring severe results once the oil or gas leaks out.

NPT is short for National (American) Pipe Thread, and it is American standard for 60° taper pipe threads, which is the same one Chinese standard ZG (now is known as NPT). NPTF (or FNPT) refers to female thread in NPT, and MNPT refers to male thread in NPT.

Does NPT fit BSP?

From the above, we knows that the NPT is 60 degree taper pipe thread, but BSPT is 55 degree thread. Therefore, NPT couldn’t fit BSP. But you can use ZG thread to fit NPT, they are the same thread type.

Kaysuns provide high pressure fittings with BSPT and NPT thread, you are welcome to contact us if you have any requirement about stainless steel thread fittings.