Types of threads: BSP threads

21 January 2015 / By: rmmcia

Rafael Márquez Moro y Cia. uses standard EN ISO 228-1 to produce threads of the standard catalogue brass fittings for threaded tube and pipe. This type of thread is also known as BSP parallel thread (cylindrical) or "Gas" thread (G).


The cylindrical thread to ISO 228-1 is a type of Whitworth thread, a name derived from the inventor of it and whose origins date back to England in the mid-nineteenth century. Whitworth shape is based on a thread with thread angle of 55 degrees, with rounded crests and roots. This type of thread became the most widely used for connecting threaded pipe and emerged as the de facto British Standard, which became known as standard threaded British pipe or BSP (for its acronym: British Standard Pipe ), in two variants: conical (BSPT, t "tapered"), and in its parallel or cylindrical shape (BSP, the last p of "parallel").

As mentioned, the BSP threads are threads with profile "Gas" and can be of two types:
Parallel: male and the female are mounted on the same cylindrical thread. Denomination according to ISO 228-1 is G.
   Denomination example: 1/2" thread BSP parallel → G 1/2.
Tapered: the conical male can be installed on a female thread conical or parallel. Denomination following ISO 7-1 (EN 10226-1) is R for external thread (male) and Rp and Rc for internal thread (female), with Rp if cylindrical and Rc when conical.
   Denomination example: male thread 1/2" BSP tapered → R 1/2.


In Rafael Márquez Moro y Cía. we also manufacture conical threads on request, according to standard ISO 7-1 or others, such as the American standard NPT (National Pipe Thread), which also defines conical thread and we will talk some other time. Please contact us if it is your case and you need manufacture on request according to your specifications.

For more technical information you can ask us or refer directly to the rules:
 UNE-EN ISO 228-1: Pipe threads where pressure tight joints are not made on the threads. Part 1: Dimensions, tolerances and designation.
 UNE-EN 10226-1: Pipe threads where pressure tight joints are made on the threads. Part 1: Taper external threads and parallel internal threads. Dimensions, tolerances and designation.

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