When checking and replacing your couplings and fittings, you will need to know how to measure their BSP (British Standard Pipe) threads. These can be BSPP, where they are parallel, sealed by a washer or an ‘O’ ring seal or BSPT, where they are tapered along their length, sealing with mating male and female threads.
This is a common confusion leading customers to question the replacement and spare parts that they actually need for their machine. We want to help abolish this ambiguity in choosing your correct couplings, so take a look at the measurement guide below so you know exactly what to look for.
First, to determining the thread size:
-
Measure the outer diameter (OD) of the thread (in inches)
-
Then subtract 25% from this (¼ inch)
-
Therefore, if the OD of a BSP thread measures 1”, the thread size will be ¾ . This is often written in shorthand as a Dash Size and this particular one would be written as -12.
- You’ll then need to make sure it is a BSP fitting so by counting the threads on your coupling, perhaps only just over ¼”, you can just multiply this by four to find the threads per inch. You can then match this measurement against the table below, to find the exact dimensions for your fittings.
|
BSP Thread Size |
Outside Diameter mm / inch |
TPI |
|
1/16 Inch BSP |
7.7 mm / 0.304" |
28 |
|
1/8 Inch BSP |
9.7 mm / 0.383" |
28 |
|
1/4 Inch BSP |
13.16 mm / 0.518" |
19 |
|
3/8 Inch BSP |
16.66 mm / 0.656" |
19 |
|
1/2 Inch BSP |
20.99 mm / 0.825" |
14 |
|
5/8 Inch BSP |
22.99 mm / 0.902" |
14 |
|
3/4 Inch BSP |
26.44 mm / 1.041" |
14 |
|
7/8 Inch BSP |
30.20 mm / 1.189" |
14 |
|
1 Inch BSP |
33.25 mm / 1.309" |
11 |
|
1-1/4 Inch BSP |
41.91 mm / 1.650" |
11 |
|
1-1/2 Inch BSP |
47.80 mm / 1.882" |
11 |
|
2 Inch BSP |
59.61 mm / 2.347" |
11 |
|
2-1/4 Inch BSP |
65.71 mm / 2.587" |
11 |
|
2-1/2 Inch BSP |
75.18 mm / 2.96" |
11 |
|
3 Inch BSP |
87.88 mm / 3.46" |
11 |
|
4 Inch BSP |
113.03 mm / 4.45" |
11 |
|
5 Inch BSP |
138.43 mm / 5.45" |
11 |
|
6 Inch BSP |
163.83 mm / 6.45" |
11 |
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