BSP Thread Pitch Chart

What is a BSP Thread?

BSP stands for British Standard Pipe, a widely recognised pipe thread standard used internationally for connecting pipes, fittings and components in countless applications. BSP threads feature a distinctive 55° Whitworth thread form, which differs from other thread standards and provides reliable performance in demanding environments.

One important characteristic of BSP threads is that they are commonly identified by their nominal pipe size rather than the actual outside diameter of the thread. This can initially seem confusing, but it's a standardised convention that makes identification straightforward once you understand the system. BSP threads are extensively used throughout Australia and internationally in plumbing, hydraulic, pneumatic and industrial applications where reliable, pressure-tight connections are critical.

There are two main types of BSP threads, each designed for different sealing requirements:

• BSPP (British Standard Pipe Parallel) – also known as G thread – uses a parallel thread form and generally requires sealing with washers, O-rings or thread sealants to create a leak-free connection.
• BSPT (British Standard Pipe Tapered) – also known as R thread – uses a tapered thread form specifically designed to create a pressure-tight seal without additional sealing components.

How to Read the BSP Thread Chart

The BSP Thread Chart above provides essential reference data for engineers, machinists and technicians. Each column contains specific information to help you select the correct tools and fittings:

• Diameter – The nominal pipe size (e.g., 1/8", 1/4", 1/2") used to identify the thread.
• TPI (Threads Per Inch) – The number of thread peaks per inch, which determines the thread pitch and affects tool selection.
• Drill Size (mm) – The tap drill size required when creating BSP threads, specified in millimetres for precision.

It's important to remember that BSP thread sizes do not equal the measured outside diameter of the thread. The nominal size is a standardised reference, and the actual outside diameter will differ. This is why consulting a reliable BSP Thread Chart is essential when selecting taps, dies, drill bits and other threading tools.

Common Applications for BSP Threads

BSP threads are found in a diverse range of industrial, commercial and domestic applications across Australia and globally. Common uses include:

• Hydraulic systems and components
• Pneumatic equipment and air lines
• Plumbing applications and water systems
• Pumps, valves and flow control devices
• Compressed air systems and tools
• Industrial machinery and equipment
• Agricultural equipment and irrigation systems
• Engineering workshops and manufacturing facilities

The versatility and reliability of BSP threads make them the standard choice for professionals who demand consistent, dependable connections in critical applications.

Frequently Asked Questions

What does BSP stand for?
BSP stands for British Standard Pipe. It is an internationally recognised pipe thread standard used for connecting pipes, fittings and components.

What is the difference between BSPP and BSPT?
BSPP (Parallel) uses a parallel thread and requires additional sealing components like washers or O-rings. BSPT (Tapered) uses a tapered thread designed to create a pressure-tight seal without additional sealing.

Are BSP threads the same as NPT threads?
No. BSP and NPT (National Pipe Thread) are different standards. BSP uses a 55° Whitworth thread form, while NPT uses a 60° thread form. They are not interchangeable and require different tools.

Are BSP threads still used in Australia?
Yes. BSP threads remain the standard for plumbing, hydraulic, pneumatic and industrial applications throughout Australia and are widely used by engineers, machinists, plumbers and maintenance technicians.

How do I identify a BSP thread size?
BSP threads are identified by their nominal pipe size (e.g., 1/8", 1/4", 1/2"). Consult a BSP Thread Chart or measure the thread pitch and outside diameter to confirm the size.