The BSP thread standard is the British Standard Pipe (BSP) thread, which is widely employed in various industrial, domestic, and agricultural sectors for a wide variety of applications including hydraulic, pneumatic, and water systems.
This BSP thread size guide provides you with essential information on their sizes, types, and some important considerations to keep in mind. So don’t be scratching your head in despair when looking at BSP fittings – simply grab a set of vernier calipers and get that fitting measured up.
Please be aware that there will be some slight variance in our quoted figures (+-) decimals of a mm due to differences within the manufacturing process.
Amazon Affiliate Links
Male BSP Thread Size Guide –
To help you quickly identify the correct male BSP thread size, refer to our following conversion chart:
| Nominal Size (inches) | Outside Diameter (mm) | Threads per Inch (TPI) |
|---|
Amazon Affiliate Links
Female BSP Thread Size Guide –
To help you quickly identify the correct inside port female BSP thread size, refer to our following conversion chart:
| Nominal Size (inches) | Inside Port Diameter (mm) | Threads per Inch (TPI) |
|---|
Quick Fire BSP Thread Size Guide –
For BSP Male Threads-
What BSP size is a 9.7mm external diameter measurement?
A 9.7mm external diameter measurement is ⅛-inch BSP.
What BSP size is a 13.1mm external diameter measurement?
A 13.1mm external diameter measurement is ¼-inch BSP.
What BSP size is a 16.6mm external diameter measurement?
A 16.6mm external diameter measurement is ⅜-inch BSP.
What BSP size is a 20.9mm external diameter measurement?
A 20.9mm external diameter measurement is ½-inch BSP.
What BSP size is a 22.9mm external diameter measurement?
A 22.9mm external diameter measurement is ⅝-inch BSP.
What BSP size is a 26.4mm external diameter measurement?
A 26.4mm external diameter measurement is ¾-inch BSP.
What BSP size is a 33.3mm external diameter measurement?
A 33.3mm external diameter measurement is 1-inch BSP.
What BSP size is a 41.9mm external diameter measurement?
A 41.9mm external diameter measurement is 1¼-inch BSP.
What BSP size is a 47.8mm external diameter measurement?
A 47.8mm external diameter measurement is 1½-inch BSP.
What BSP size is a 59.6mm external diameter measurement?
A 59.6mm external diameter measurement is a 2-inch BSP.
For BSP Female Port Threads-
What BSP size is an 8.9mm inside diameter measurement?
An 8.9mm inside diameter measurement is ⅛-inch BSP.
What BSP size is an 11.9mm inside diameter measurement?
An 11.9mm inside diameter measurement is ¼-inch BSP.
What BSP size is a 15.2mm inside diameter measurement?
A 15.2mm inside diameter measurement is ⅜-inch BSP.
What BSP size is a 19.1mm inside diameter measurement?
A 19.1mm inside diameter measurement is ½-inch BSP.
What BSP size is a 20.3mm inside diameter measurement?
A 20.3mm inside diameter measurement is ⅝-inch BSP.
What BSP size is a 24.6mm inside diameter measurement?
A 24.6mm inside diameter measurement is ¾-inch BSP.
What BSP size is a 31mm inside diameter measurement?
A 31mm inside diameter measurement is 1-inch BSP.
What BSP size is a 39.6mm inside diameter measurement?
A 39.6mm inside diameter measurement is 1¼-inch BSP.
What BSP size is a 45.5mm inside diameter measurement?
A 45.5mm inside diameter measurement is 1½-inch BSP.
What BSP size is a 57.4mm inside diameter measurement?
A 57.4mm inside diameter measurement is a 2-inch BSP.
Understanding BSP Threads
BSP threads come in two main types: BSPP (British Standard Pipe Parallel) and BSPT (British Standard Pipe Tapered). BSPP threads are straight, and their sealing is often achieved using an O-ring or washer. On the other hand, BSPT threads are tapered, allowing them to seal by the wedging action of the thread.
BSP Thread Sizes
BSP thread sizes are designated by their nominal size, which can sometimes be confusing as it doesn’t directly correspond to the actual diameter of the thread. Here’s a brief overview of common BSP sizes:
- 1/8” BSP: This small size is often used for instrumentation and pneumatic connections.
- 1/4” BSP: A versatile size, commonly used in small valves and fittings.
- 3/8” BSP: Frequently utilized in hydraulic and plumbing applications for moderate flow.
- 1/2” BSP: One of the most common sizes used in various industrial an hydraulic applications.
- 3/4” BSP: Typically used for larger flow rates in both domestic and industrial settings.
- 1” and above: These sizes are used for high-flow applications, such as in large water supply systems or in hydraulic free-flow return systems.
Caveats of BSP Measurements
While BSP threads are a reliable standard, there are a few caveats to be aware of:
- Nominal Size vs. Actual Diameter: The nominal size of a BSP thread does not correspond to its actual outside diameter. For example, a 1/2” BSP thread has an outside diameter of approximately 20.9mm. Always refer to size charts for accurate measurements.
- Compatibility with NPT: BSP and NPT (National Pipe Tapered) threads are not directly compatible. While they might appear similar, they have different thread angles and pitches, which can lead to leaks if mismatched.
- Sealant Requirements: Depending on the type of BSP thread, different sealing methods may be needed. BSPP threads often require a separate sealing mechanism, such as an O-ring or dowty washer, while BSPT threads seal on their own but may benefit from thread sealants for extra security.
- Materials Matter: The material of the fittings can affect thread engagement and sealing properties. Ensure that the materials used are suitable for the intended application and compatible with the fluids being transported.