Guide to British pipe thread sizes
Here is a comprehensive guide to British pipe thread sizes in both metric and inch measurements.
Understanding these dimensions is crucial for accurate hydraulic system setups and repairs.
Metric Thread Table – British pipe thread sizes In one table, we present British pipe thread sizes in metric terms (i.e., in millimeters) and inch terms (i.e., in “inches”—a commonly used measure in hydraulics). Many people believe that an inch in hydraulics corresponds to the same assumption as in mathematics and that such a thread must be 24mm. This is not true — 1-inch threads have been adapted over the years to pipes of such diameter. Their actual size—as well as the size of threads in any other dimension—can be found in the metric thread table (inch thread table) below:
|
Nominal Pipe Size (NPS) |
Threads per Inch (TPI) |
Outer Diameter (OD) in Inches |
Outer Diameter (OD) in Millimeters |
|
1/8″ |
28 |
0.405 |
10.29 |
|
1/4″ |
19 |
0.540 |
13.72 |
|
3/8″ |
19 |
0.675 |
17.15 |
|
14 |
0.840 |
21.34 |
|
|
14 |
1.050 |
26.67 |
|
|
11 |
1.315 |
33.40 |
|
|
1 1/4″ |
11 |
1.660 |
42.16 |
|
1 1/2″ |
11 |
1.900 |
48.26 |
|
2″ |
11 |
2.375 |
60.33 |
It’s important to note that the actual outer diameter of the pipe is larger than the nominal size. This discrepancy originates from the historical development of pipe sizes, where the nominal size referred to the inner diameter of the pipe. Over time, the wall thickness of pipes increased for strength, leading to the current standards.
For those working with British pipe threads, the proper identification and understanding of these sizes ensure compatibility and efficiency in hydraulic systems. Always double-check the thread specifications before making any connections to avoid leaks or mechanical failures.
