Here's an Overview of the ANPT 6-Step Ring Gage


ANPT or Aeronautical National Pipe Taper is a form of ring threads that are used in components like plugs, pipes, fittings, etc. The ring is particularly dedicated for aeronautical applications where equipment needs a sealing thread joint. In the stated application, O-rings or gaskets and even straight threads are not applicable.  When these rings or threads are located outside a component, we use ANPT 6-Step Ring Gage to measure the pitch diameter size of the part in question. This is essential for all dry seal or aeronautical components. The ANPT 6-Step Ring Gage is used in conjunction with the ANPT L1-ring gage.

How Is It Used?

The use of ANPT 6-step ring gage is similar to that of ANPT 6-step plug gage, just on the outside. In other words, the gage is used to check the major diameter of the male fittings and in conjunction with that, the L1 ring is used to check the thread elements that may travel across the distance that is engaged when tightened by hand. 

The ANPT 6-step ring gage is used to check the maximum and minimum truncation steps. On the ring, there are maximum and minimum truncation steps for each of the three conditions of the pitch diameter. Minimum, Basic, and Maximum. The part must fall between the B and BT steps on the ANPT 6-step ring gage if the LI ring shows it to be of the basic pitch diameter. Whereas, if the part falls between the M and/or MNT steps, it means that the L1 ring should show the pitch diameter to be of minimum diameter. Finally, if the part falls between MX and MXT steps, it means that the pitch diameter of the part as measured by the L1 gage should be of maximum diameter.

It is also vital that there should be no permissible wobbling or shaking otherwise the part may not be suitable for the application intended. Especially the truncation of lead, angles, and roots must be checked on the tool wear at every time possible by projection.

More On ANPT 6-Step Ring Gage

The application of thread ring gage is very easy, but it is still recommended to consult with the diagrams and datasheet first. It falls upon the user as a responsibility to ensure that the ring gage correctly engages all the special pitch diameters along with the major and/or minor diameters, pitches/TPI, and the class of fit. Moreover, it must also be confirmed if the gage conforms to the proper standard of the national/international standard.

Moreover, it is suggested to take care of your ANPT 6-step ring gage after every use to ensure the longevity of the product life. Ensure recalibration is conducted periodically and the gage is cleaned after each use. Keep an eye out for any chips, grits, or burrs that may cause unnecessary scratches and wear to the major/minor diameters of the thread gage along with its gage flanks.


ANPT 6-step ring gage from WESTport Corporation is ideal for measuring the external threads of pipes and/or other equipment and ensuring the said equipment or part in question falls within the said parameters. At WESTport corporation, we are at the forefront of presenting the industry’s highest quality and most affordable line of measuring equipment and tools. Using state-of-the-art technology and our world class customer service team, we are thoroughly committed to ensuring we retain our status as one of the worldwide leaders and trusted sources for precision measuring instruments.

Written by WESTport Corporation. All rights reserved. Any reproduction is strictly prohibited.