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BSP thread and G thread difference

Time : 2022-05-19 Hits : 8

Introduction of BSP thread

BSP Thread is the abbreviation of British Standard Pipe Thread, refers to the British Standard Pipe Thread, which belongs to the Category of Wyeth Thread (BS84), tooth Angle is 55°. According to the shape, BSP threads have two types: cylindrical Pipe thread BSPP (British Standard Pipe Parallel) and Taper Pipe thread BSPT (British Standard Pipe Taper).

BSPP Inch cylindrical pipe threads. The other type of pipe thread is called "conical pipe thread", which is the conventional name and the standard name in textbooks.

For historical reasons, the BSPP has also been called by other names. Common ones are BSPF (British Standard Pipe Fitting), BSPM (British Standard Pipe Mechanical), PS (British Standard Pipe Straight), etc. Later, with the beginning of ISO standardization, these various names were replaced by a simple letter G, which is the G thread. Therefore, BSPP, BSPF, BSPM and PS are now collectively referred to as G threads.

Called G thread, because the thread more than originally used in the Gas, and Gas for Gas in English, but some said G from the German Gewinde (meaning for thread), in addition, the G and tube (Guan) in Chinese pinyin first letter of the same, so about the origin of G thread, no matter from which perspective seems to be reasonable, It really is a coincidence.


G thread, internal thread and external thread, used for unsealed connection. The implementation standard is BSENISO228-1, the old standard is BS2779, has been abolished.

BSPT inch taper thread, also known as PT thread, is only used for general sealing connection. BSPT old standard is BS21, and in the new standard BSEN10226-1, replaced by R thread. So R thread is the general name of BSPT and PT thread.

The letter R in the R thread comes from the German rohr (German for "tube"). R thread is actually a series, common Rp, Rs, Rc, R1 and R2. Details are as follows:

Rp-inch seal cylindrical internal thread

Rs-inch seal cylindrical external thread

Rc-inch sealed taper internal thread

R1-inch seal taper external thread, used with Rp, i.e. Rp/R1 "column/cone" thread

R2-inch sealed tapered external thread for use with Rc, Rc/R2 "taper/taper" thread

It can be seen that the general sealing British pipe threads are divided into cylindrical pipe threads and taper pipe threads.

The design of cylindrical pipe thread (Rp) for sealing is exactly the same as that of unsealed pipe thread G, but the difference lies in the precision of the thread. The sealing tapered pipe thread (R) is converted to a taper of 1:16 on the basis of the cylindrical pipe thread.


General sealing with cylindrical pipe thread (Rp) sealing effect is through the throughout the thread if necessary add sealing filler (such as: ptfe sealing tape), rather than the seal with a cylindrical pipe thread sealing effect (G) is through around the ends of the threaded connection or its use sealing devices (such as: type O sealing ring).

In addition, there are differences in the use and design tolerances of common sealing and non-sealing pipe threads.

In fact, many mechanical processing enterprises in the processing of BSP threads usually encounter thread ring plug gauge inspection is qualified but together is the case of poor sealing the main reason lies in the confusion of sealing Rp internal thread and non-sealing G internal thread.

The difference between BSP thread and G thread

G-inch cylindrical pipe thread (standard: BS2779, BSENISO228-1, ISO7-1)

BSPPinch cylindrical pipe thread (standard: BS2779, BSENISO228-1, ISO7-1)

BSPT-inch taper pipe thread (standard: BS21, BSEN10226-1, ISO7-1)

R (Rp, Rs, Rc, R1, R2) - Inch taper pipe thread (standard: BS21, BSEN10226-1, ISO7-1, DIN2999)