Identifying and measuring threads can sometimes be the hardest part of any fluid-related project. Damaged threads or damaged fittings can often lead to misidentification and constant headaches. By using the simple steps below and by using our Universal Thread identification kit, you can easily distinguish any fitting to ensure you can get the parts you need the first time.




1) Look at the Nut to Identify the fittings

-If you have a Tube fitting that has female threads or you have compression fitting with a Tube nut, there should be a set of numbers and a letter located on the back side of the nut. This set of numbers and letters will determine the size of your fitting.

Look for the numbers and letters stamped on the nut.

2) Measuring the Threads and Thread Pitch

– If your female thread does not have a stamped number on it or you do not have the tube nut, you will need to use a set of calipers and a thread pitch gauge to determine the proper size.

Step 1: Identify the Tube size

First, you need to use your calipers to measure the ID of the fitting right before the shoulder (or shelf). Using this measurement, you can determine the threads using the thread identification chart in your MSIK1 or in the link below.

Step 2: Measure the OD of the threads

After confirming your tube size, you will then measure the OD of the threads. When measuring the threads, be sure to have the calipers measuring straight across the fitting versus at an angle to get the correct measurement.

Step 3: Measuring the Thread Pitch

When completing the other two measurements, The last thing that needs to be done is to measure the thread pitch using a thread pitch gauge. These gauges and the calipers come included in our Thread ID kit.

After measuring all three points look onto the chart below to decide what size your fitting is. If you don’t know what it is to contact us, and one of our trained salesmen can help you get the parts you need!


Thread Identification Chart
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Malone Specialty Inc.

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