How to Measure Plumbing Fittings
You may not be familiar with the standard thread sizes for plumbing fittings. The British Standard Pipe Thread (BSP) is a very common size, but it doesn’t always match up with the scale of a ruler. A 1/2″ BSP thread, for example, will measure more like 3/4″ on a ruler. This is because the BSP thread size is based on the inside diameter of the steel pipe and the outside diameter of the male thread. how to measure plumbing fittings uk
There are two types of threads for pipe and fittings: tapered (BSPT) and parallel (BSPP). If you are looking for a British Standard Pipe coupling, you should first learn the threads’ length. This is because a British Standard Pipe coupling requires a thread that is 30 degrees longer than the thread of the coupling. You will need to know these threads in order to get the correct fit.
To measure BSPT fittings, you should use a calliper to read the inside diameter (ID). BSPT is also known as a dash size, and it corresponds to the ID measurement in increments of 0.0625 inches, so a -6 dash size relates to a 6/16″ ID. You should also know the thread pitch, which refers to the distance between the two adjacent threads. This distance must be measured at the crest of the thread. Once you have these two measurements, you will need to determine the OD (outer diameter) of the fitting.
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