Tagged with pipe fittings sizes

How To Measure and Identify Hydraulic Threads

This is something I often get asked; ” How do I know what thread it is?

Our aim is to deliver you with all the help you need to successfully measure and identify hydraulic fittings threads, by using this thread guide.  Hopefully by the end of reading this post you will be a little more informed, and find the process less daunting.

First off, we have a PDF guide on the website, which covers the size range, and I will reference to this in the post as it has all the technical data in there.

If you want to download, save and print a copy of the thread guide, then please visit the link here.


Things will you need:

  • Thread/Pitch Tool – (Ideally)
  • Vernier Calipers - Preferably digital and calibrated for a more accurate reading (Essential)
  • A variety of fittings for testing this out on

The first thing to do is establish is the thread gender,  do we have a “male” or “female” thread? The easiest way to see this is, Is the thread on the outside (male) or on the inside (female)

Below is a bush – this shows both the male and female thread. With the male on the outside

After we have looked at the fitting, and identified the gender, we can then measure it using the vernier callipers.  As you can see from this fitting, it is a male thread, and I have got a measurement of 20.81mm . In some cases this may be enough to identify the fitting, but to be certain we would also confirm the seat angle, and the Threads Per Inch (TPI)

Looking at my hydraulic thread guide PDF, on page 3, under the BSP threads, and the male thread OD mm column, I can see a size 1/2″ has a male thread OD of 20.8mm. The 1/2″ ORFS on Page 5 comes close at 20.6mm, all the other threads are too far out.

So we move on to the TPI, where the BSP has  14 TPI and the ORFS has 16 TPI. This is where we would use a thread pitch tool. Using my pitch guide I can see this is 14 TPI

If you do not have this tool, there is another way. But I must state this is a rough guide, and do not want to be held responsible. Using the vernier we can count the threads across a 1″ measurement, or 1/2″ measurement, then double that number. This isn’t the most accurate way, but it will do if you do not have all the tools.

But the main difference in the BSP threads and the ORFS, is the seating. The BSP usually has  a 60° cone seating, whereas the ORFS has a O Ring in the face of the male thread.

Some tools will have a seating angle measurement as well. Using the tool I can see this is a 60° cone seating, which confirm to me this is definitely a 1/2″ ( -8 ) BSP Thread.

If you are not confident measure threads, we can of course guide you through it , or you send in your fittings and we will identify them. We can make hoses to your specification without you having to call out an on=site hydraulic hose repair company.






Tagged , , , , , , ,