Overview of Taper Pipe NPTF 6 Step Plug Gages


Taper pipe NPTF 6 step plug gage is used in conjunction with L1 plug to inspect the profile of the internal threads or crest truncation. In other words, its purpose is to measure the pitch diameter size of the essential components of the dry seal. It ensures conformance to dry seal requirements because to get an accurate measurement, it is vital to determine the distance from the L1 gage to the part.

More About Taper Pipe NPTF 6 Step Plug Gage

The 6-steps plug gage is used for testing the root or crest of the product thread in question. Since the three zones of the gage are overlapping, we need six steps for measurement. These six steps are as follows:

  • MX
  • MXT
  • B
  • BT
  • MN
  • MNT

How Does It Work?

If the result of the L1 gage indicates that a part falls in the minimum range, then it must fall between B and BT on the Taper pipe NPTF 6 step plug gage. If the part lies in the basic range, then it must fall between B and BT on the Taper pipe NPTF 6 step plug gage. Finally, if a part lies in the maximum range, it must fall between MX and MXT on the Taper pipe NPTF 6 step plug gage.

Taper pipe NPTF 6 step plug gage is required by the NPTF class 2 threads. It is also known by another name which is Crest-and-Root Truncation Gage. Taper pipe NPTF 6 step plug gage is not threaded, rather, it has six steps grounded into it. The tool is used by inserting it into the hole and then reading the pairs which tell us the high and low limits of the three aforementioned conditions.

This extra check is required by the class 2 threads. These gages are designed to the specifications of the Bureau of Standards Handbook H-28 and ANSI Standards B1.20.3 and comply with MIL-P-7105 Military Standards.


Taper pipe NPTF 6 step plug gage is essential for the measurement of the Crest-and-Root Truncation. Having no threads of its own, it has 6 steps that help in the identification of the thread in either minimum, basic, or maximum condition. They help us in gaging the internal diameter of holes that have been drilled into parts or machines. They are an essential tool for every quality control agent, engineer, machinist, or inspector to get an idea of the characteristics of the part in question.

These measuring methodologies are essential and prevent the employment of difficult methodologies for measurement that may be more time consuming or simply not implementable for everyone. Based on that, a part is either accepted or rejected. At WESTport we offer a wide range of the highest quality precision tools, taps and dies, gages, and full-service ISO 17025 metrology laboratories for tool calibration, repair and onsite services. We are continuously improving our services and products to maintain our position as a global leader in our industry.

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