Thread identification and measure BSPT & BSPP Fittings

If there is any confusion about which type or size of fitting you have, you'll need to know how to measure your BSP fittings. You can identify any BSPP or BSPT fitting accurately by measuring across the thread from one side to the other. BSPP fittings can be measured more simply, and their specifications can be identified with a few basic calculations.

How determine the thread size:

1. Measure the thread's outer diameter (OD) in inches.
2. Subtract 1/4 inch (0.25") from the OD measurement.

So if the OD of a BSPP male thread measures one inch (1"), the thread size will be 3/4. In the chart, you'll also see Dash Sizes, which are a convenient shorthand reference for identifying the type. In this example, the thread size would be -12.

The next step is to count the number of threads you have per inch on the fitting to confirm that it is actually a BSP fitting. The easiest way is to count the thread crests over a shorter length, say 1/4", and simply multiply it by 4.

 For example, if you count 3.5 thread crests over 1/4":

• 3.5 x 4 = 14 threads per inch.
• Take this measurement and cross-reference it to your thread size in the chart below.

This will match your measurements with the standard BSP sizes and their associated specifications.

note: Each dash size corresponds to a progressively larger diameter, measured in sixteenths of an inch. “-1” is 1/16, “-2” is 2/16, and so on. In this case, -6 hose would indicate a hose with an inside diameter of 6/16”, or 3/8".

more example: -08 corresponds to 8/16", or 1/2".

Below the automatic equivalent calculation

Conclusion:

Regarding BSP fittings there are a lot of confusion. What matters it is the identification correctly like in this manual.

Below th details:

1. Measurement OD if fitting is male or ID if is female
2. Subtract 1/4" from the value (0.25")
3. Identify the inch and dash in the table above
4. Count the thread crests and calculation like in the example above

Note: The fittings NPT and BSP are not interchangeable, below the difference

Both threads have the same pitch and the familiar shaped peaks and valleys. However, the designs of the threads differ in two fundamental ways. With NPT, the peaks and valleys of the threads are flat. In BSP, they are rounded. Secondly, the NPT angle of the thread is 60 degrees and the BSP angle is 55 degrees (see photos below).

BSPT Fittings	NPT Fittings

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