How to Measure BSP Threads Leave a comment

getty images U7CFqPwAnD4 unsplash

In the realm of pneumatic and hydraulic systems, accurate measurement of BSP (British Standard Pipe) threads is crucial for ensuring reliable and leak-free connections. Fluid-Air Components Ltd, with its extensive experience in supplying pneumatic products and process valves, understands the importance of precision in this area. Measuring BSP threads correctly not only guarantees the effectiveness of your fittings but also enhances the overall efficiency and safety of your system. In this guide, we will take you through the essential steps and techniques to accurately measure BSP threads, ensuring that you select the right fittings for your applications.

In the next section, we’ll delve into understanding British Standard Pipe (BSP) fittings, laying the foundation for accurate measurement techniques.

Understanding British Standard Pipe (BSP) Fittings

BSP fittings are a staple in the UK and many other parts of the world, renowned for their reliability in connecting pipes and hoses in pneumatic and hydraulic systems. Characterised by their fine threads, BSP fittings come in two main types: BSPP (British Standard Parallel Pipe) and BSPT (British Standard Pipe Tapered). The distinction lies in the thread form; BSPP threads are parallel, while BSPT threads are tapered, offering different sealing mechanics.

Fluid-Air Components Ltd, with its expertise in industrial hose and pneumatic products, recognizes the subtleties in these two types of connections. The company offers a wide range of both BSPP and BSPT fittings, catering to diverse industrial needs. Understanding these fittings is the first step towards accurate measurement. The correct identification and measurement of these thread types ensure a secure fit and prevent potential leakage or fitting failure.

Moving forward, we will explore the specific methods for measuring BSPP and BSPT connections, a critical step to ensure you select the correct fitting for your application.

Measuring BSPP and BSPT Connections

When it comes to measuring BSPP and BSPT connections, the approach varies slightly due to their different thread shapes. For BSPP threads, the focus is on the diameter and the number of threads per inch, as the parallel design necessitates an exact diameter match for a proper fit. On the other hand, BSPT fittings, with their tapered threads, require careful measurement of both the thread diameter at various points and the thread pitch.

At Fluid-Air Components Ltd, understanding the nuances of these measurements is part of our commitment to providing the best pneumatic solutions. For instance, when measuring a BSPT connection, it’s crucial to note that the diameter decreases along the length of the fitting. This tapering is what allows for a tighter seal in tapered threads, a feature absent in parallel threads.

Accurate measurement of these threads is not just about finding the right size; it’s about ensuring efficiency and safety in your pneumatic system. Next, we will delve into the techniques for determining thread diameter and pitch, an essential skill for anyone working with BSP fittings.

Determining Thread Diameter and Pitch

The precision in determining the thread diameter and pitch is pivotal for the correct specification of BSP fittings. Thread diameter is the width of the thread at its widest point. For BSPP threads, this measurement remains consistent along the length of the thread. In contrast, BSPT threads taper, so their diameter is measured at the end of the fitting for a consistent reference point.

Pitch, the distance between thread crests, is equally important. It’s measured in threads per inch and is crucial for ensuring that the fitting matches the internal thread of the component it’s being screwed into. A mismatch in pitch can lead to cross-threading, which not only damages the fitting but also compromises the integrity of the entire system.

Fluid-Air Components Ltd employs these precise measurements in its extensive product range, ensuring that each component fits seamlessly into a variety of pneumatic systems. Our technical expertise allows us to guide customers in selecting the correct fittings, taking the guesswork out of these crucial measurements.

Next, we will provide a step-by-step guide on thread size calculation, simplifying what might otherwise be a complex process. This guide is designed to empower our customers with the knowledge to make informed decisions about their pneumatic fittings.

Thread Size Calculation: A Step-by-Step Guide

Calculating the size of a BSP thread involves a few straightforward steps, allowing for accurate determination of the fitting size required for any application. This process is vital for ensuring a perfect match between the thread of the fitting and the corresponding component.

Identify the Type of BSP Thread

Start by determining whether the thread is BSPP or BSPT. This identification is crucial as it influences how the measurements are taken.

Measure the Outer Diameter

For BSPP threads, use a calliper to measure the outer diameter of the thread. In the case of BSPT threads, measure the diameter at the end of the fitting. It’s important to measure accurately to the nearest hundredth of a millimetre for precision.

Count the Threads

Carefully count the number of threads over a one-inch length. This count is your thread pitch, a key factor in matching threads.

Determine the Thread Size

Once you have the diameter and pitch, refer to the BSP thread chart below to determine the nominal thread size.

(Nominal Size)Thread PitchMale Thread OD mmMale Thread OD inchesFemale Thread ID mmFemale Thread ID inches
1 ¼”1141.91.65”39.61.56”
1 ½”1147.81.88”45.51.79”
*OD = Outside Diameter ID = Inside Diameter

At Fluid-Air Components Ltd, we utilise this methodical approach in our consultation and product selection process, ensuring that our clients receive fittings that precisely match their system requirements. Our expertise in pneumatic components allows us to provide tailored solutions, even for the most complex applications.

In the next section, we will explore the use of a vernier calliper for measuring BSP fittings, a tool that brings an added layer of accuracy to these measurements. This tool is integral to achieving the precision required in pneumatic systems.

Utilising a Vernier for BSP Fittings

A vernier calliper is an indispensable tool in the precise measurement of BSP fittings. Its ability to measure both internal and external diameters with high accuracy makes it ideal for determining the exact size of BSP threads. This precision is crucial, especially in pneumatic systems where even a minor mismatch can lead to inefficiencies or safety issues.

When using a vernier calliper to measure BSP fittings:

  • For External Threads: Place the jaws of the calliper around the thread’s widest part to measure the outer diameter. Ensure the calliper is straight and not tilted for an accurate measurement.
  • For Internal Threads: Use the smaller jaws at the top of the calliper to measure the inside diameter of a fitting. This measurement is particularly important for BSPP threads where the fit must be exact.

Fluid-Air Components Ltd advocates for the use of vernier callipers in measuring BSP fittings due to their precision. This level of accuracy ensures that our customers receive fittings that perfectly match their system’s requirements, thereby eliminating the risks of leaks or thread damage.

Next, we will explore the differences between BSP and NPT (National Pipe Thread) fittings. Understanding these differences is essential for anyone working within pneumatic and hydraulic systems, as it aids in the selection of the correct fitting type for specific applications.

BSP vs NPT (National Pipe Thread) Fittings: Understanding the Differences

The distinction between BSP (British Standard Pipe) and NPT (National Pipe Thread) fittings is a crucial aspect of pneumatic system design. While both are used for creating tight seals in piping and tubing, their applications and thread forms differ significantly, impacting compatibility and performance.

BSP threads, commonly used in the UK and other parts of the world, come in two types: BSPP (parallel) and BSPT (tapered). They are characterised by a consistent thread angle of 55 degrees. NPT threads, predominantly used in North America, are tapered and have a thread angle of 60 degrees. This slight difference in angle affects how the threads create a seal and dictates their interchangeability.

One of the primary differences lies in the sealing method. BSPT and NPT threads seal by the interference of the threads themselves, whereas BSPP threads require a bonded seal or O-ring to ensure a leak-proof connection. This distinction is critical when selecting the appropriate fitting for a specific application, as using the wrong type can lead to leaks or thread damage.

At Fluid-Air Components Ltd, we understand the importance of selecting the right thread type for each application. Our expertise allows us to guide customers in distinguishing between BSP and NPT fittings, ensuring optimal compatibility and performance in their pneumatic systems.

As we conclude this guide, we’ll summarise the key points and provide final insights on ensuring the effective measurement and selection of BSP fittings. This conclusion will encapsulate the importance of precision in pneumatic systems and the role of expert guidance in achieving it.


In conclusion, the accurate measurement and identification of BSP threads are fundamental to the integrity and efficiency of pneumatic systems. Understanding the nuances between BSPP and BSPT connections, and the distinction from NPT fittings, is crucial for ensuring that the correct components are selected and applied. The use of precise tools like vernier callipers plays a vital role in these measurements, providing the accuracy needed for optimal system performance.

Fluid-Air Components Ltd, with its extensive range of pneumatic products and deep technical knowledge, stands as a valuable resource in this domain. Our commitment to quality and customer service ensures that we not only supply the right products but also impart the necessary knowledge and guidance for their correct application. Whether it’s selecting the appropriate fittings, understanding thread types, or navigating the complexities of pneumatic systems, our expertise is aimed at delivering solutions that enhance system reliability and efficiency.

As we continually expand our product range and deepen our technical expertise, we remain dedicated to helping our customers navigate the intricacies of pneumatic systems, ensuring they achieve the precision and performance they require. This commitment to excellence is what sets Fluid-Air Components Ltd apart and makes us a trusted partner in the pneumatic industry.

Enjoy this? Check out What are the Main Components of a Pneumatic System next.

Leave a Reply

Your email address will not be published. Required fields are marked *