British Standard Pipe Threads are some of the commonly used types of threads you can find, but do you know how to identify them? If you’re not keen on a second trip to the shop after buying the wrong sort, keep reading to learn how to easily tell BSP threads from other varieties.

What Does British Standard Pipe (BSP) Thread Mean?

To properly identify them, you’ll first have to know exactly what these threads are.

Technical standards exist that identify particular screw threads as BSPs (British Standard Pipe). Pipes and fittings are interconnected and sealed according to these standards around the world.

Plumbing and pipefitting in most countries is done with British Standard Pipe, which means they’re very common and easy to find. However, North America is an exception, where NPT (National Pipe Thread) is more frequently used.

How do BSP Threads Work

Identifying the male and female portions is key to correctly using BSP screw threads. Threads with an external shape are male threads, while threads with an internal shape are female threads. In order to seal these two pieces together, the external shape needs to be tightly twisted into the internal shape.

What are the threads used for?

There are different functions for different thread types.

Tapered threads are most often used for pipes that require steadfast tightening. This is because the tapered head allows for an airtight seal to be created between the two pipes. They’re a great option if you require any form of liquid to run through connected pipes, since the threads butt against each other and create a form of leak-proof pressure seal.

Straight threads serve the function of being a connecting link between two pipes. They can be used to enclose gases, steam, and fluids.

Straight threads are also very useful fittings. But, they are usually used just as a connector between two pipes. They’re an essential component of power plant machinery, as well as for fossil fuel and manufacturing industries. Straight heads are steadfast, and they can be trusted to hold dangerous chemicals.

In ships, BSP threading is commonly used for pressure systems, whilst oil and gas machines use NPT threading.

Despite this, these threads are not only used for piping. Materials of various types have been adapted to BSP as well as NPT. PTFE, copper, bronze, PVC, and nylon can all be seen with both types of threading.

Types of BSP Thread:

BSP threads come in two different forms:

– Parallel (BSPP)

– Tapered (BSPT)

For both of these threads, the flank angle is 55°.

NPT and tapered threads look fairly similar, so you’d be forgiven for thinking they’re the same thing. The way to tell one from the other is by looking at the flank angle: an NPT has an angle of 60, compared to tapered which is 55. You can check which is which by using a thread gauge which measures this.

BSP Thread Measurements

BSP threads are measured in imperial measurements such as 1/8, 1/4, 1/2, 3/4 etc.

BSP parallel threads are typically sealed by chamfering the male thread to provide a 30° cone within the female thread (certain models only).

Thread dope or Teflon tape can be used to provide additional support for tapered BSP threads. To ensure an effective seal in parallel thread applications, an o-ring and a washer or bonded washer are needed.

Have a look at these BSP thread capacities:

Follow These Steps to Identify a BSP Thread Fitting:

  1. Check whether the threads are parallel or tapered.
  1. Using a thread gauge or calipers, count the threads per inch (TPI).
  1. Using calipers, measure the thread O.D. (male thread) or I.D. (female thread).
  1. Combine your O.D. or I.D measurement with the TPI you measured and find a match on the adjacent chart.
  1. Identify the type of British fitting it is with the seal or angle sealing surface if it exists on the chart to the right.

You might also be able to tell a BSP thread from looking at its sizing.

BSP Pipe Thread Sizes

There are at over 41 thread sizes, ranging from 1/16 to 18:

  • 1/16
  • 1/8
  • 1/4
  • 3/8
  • 1/2
  • 5/8
  • 3/4
  • 7/8
  • 1
  • 1-1/8
  • 1-1/4
  • 1-3/8
  • 1/1/2
  • 1-5/8
  • 1-3/4
  • 1-7/8
  • 2
  • 2-1/4
  • 2-1/2
  • 2-3/4
  • 3
  • 3-1/4
  • 3-1/2
  • 3-3/4
  • 4
  • 4-1/2
  • 5
  • 5-1/2
  • 6
  • 7
  • 8
  • 9
  • 10
  • 11
  • 12
  • 13
  • 14
  • 15
  • 16
  • 17
  • 18

It's worth noting that only 15 of these thread sizes are ISO 7, and only 24 of them are ISO 228.

Each of these numbers was derived from the inner diameter of the steel tube into which each thread was supposed to fit, measured in inches.

The introduction of modern pipes, on the other hand, altered this strategy. To conserve material, modern pipelines have thinner walls. The pipes have a bigger inner diameter as a result of this construction.

Due to this, the present standard metric version is only a size number. The given size is the measurement of the primary outer diameter of the external thread with these metrics.

This is a bit different for a taper thread. The gauge length diameter is measured from the thread's smaller end. The thread pitch is multiplied by one to get the gauge length.

When a taper measurement is 1:16, it means that the diameter increases by one unit for every 16 units from the end.

A Guide to BSP Thread Names

A BSP thread name is made up of several components.

"Pipe thread" is a term used to describe:

  • The standard's document number
  • The most popular abbreviation for the type of pipe thread
  • The thread diameter

The following are some common symbols for pipe threads:

  • R, external taper (ISO 7). Rp, internal parallel (ISO 7/1) G, external and internal parallel (ISO 228) R, external taper (ISO 7) Rp, internal parallel (ISO 7/1). Rs, external parallel Rc, internal taper (ISO 7).

A pipe thread, for example, might be referred to as: EN 10226 Rp 2-1/2 pipe thread.

The majority of threads are right-handed. When a thread is left-handed, however, we add "LH" to the end of the name.

If the above example were left-handed, it would be as follows: EN pipe thread.

Hopefully having read a little more into BSP threads, you’re now able to identify them and know how and why they’re so commonly used. If you’d like to know more, have a look at our blog page where we cover the ins and outs of various thread types.

ThreadTools has the BSP Threads You Need

Understanding and familiarising yourself with the British Standard Pipe requirements is critical, especially if you’re in a region where they’re the standard.

Even more crucial than understanding the regulations, you must ensure that you are receiving high-quality equipment for your work.

This is where we can help.

We can assist you in locating the BSP threads that you’re after at Wiseman Thread Tools. Each and every one of our threads and tools is high quality and fully reliable for your needs. Contact us here to learn more about how we can help.