Glossary Thread limit plug gauges

Thread plug gauges belong to the group of thread gauges and are used for testing internal threads.

They combine both a thread plug gauge and a thread limit plug gauge on one handle.

Thread plug gauges therefore have two sides that represent the maximum and minimum permissible dimensions of the thread to be tested. One side has a standardized thread with nominal dimensions and is referred to as the good side. The other side is the reject side, which is marked by a red ring. The dimensions of the thread on the outlet side correspond to the tolerance limit.

The gauge is screwed into the thread by hand for gauging. Both sides are used to check whether the actual dimension of the thread is within the permissible tolerances.

The result of the test is not a measured value, but a classification as “good” or “reject”.

Due to mechanical stress, thread plug gauges increasingly wear out. They are therefore preferably manufactured from high-strength materials or hard-coated as CNC turned parts. As part of testing and calibration, thread plug gauges must be checked at fixed intervals.

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