It is wise to check the thread of connectors and adapters upon incoming inspection. Out of limits thread can create serious problems and may damage the connectors of mating components or ruin the connectors at the test equipment. Spectrum Elektrotechnik GmbH offers a comprehensive line of thread limit gauges to check the thread on a “GO” / “NO GO” basis.
The Gauge is used to check the thread of the female connector.
With this Gauge the pitch diameter, pitch angle and number of threads per unit are being examined. The gauge needs to thread on easily up to the very end of the threaded area, without having any force applied.
NO GO GAUGE
It must thread on no more than two revolutions. If the gauge does thread on, and without being forced, more than two revolutions, then the thread is below the allowable minimum limit, the thread pitch diameter is too small.
The gauge is used to check the coupling nut thread of the male connector.
The Gauge examines the pitch diameter, pitch angle and number of threads per unit. It needs to thread in easily, up to the very end of the threaded area of the coupling nut, without the need to have any force applied.
NO GO GAUGE
It must thread into the coupling nut no more than two revolutions. If the gauge does thread in without being forced, more than two revolutions, then the thread is above the allowable maximum limit, the thread pitch diameter is too big.
A complete Set consists of two Ring Gauges and one Bolt Gauge and is supplied in an instrument case. The Gauges are available for each of the connector series, as listed below.
ISO METRIC THREAD
The thread is marked with the letter “M” for metric. The diameter and the pitch are in millimeters. The pitch is the distance from a point on the thread to a corresponding point on the adjacent thread. Example: M7 x 0.75 has a 7mm diameter and threads which measure 0.75mm from one point to its corresponding point.
The pitch diameter is defined as the diameter of a cylinder that passes through the thread profile to make the width of the thread ridge and thread groove equal on both sides of the thread and parallel to its axis. The Pitch diameter is the primary control and reference datum for measuring threads.
It determines first the kind of thread, either Unified Inch Thread or ISO Metric Thread and involves then functional size and pitch, and pitch diameter, including angle, lead and chamfer.
UNIFIED INCH THREAD
The thread is characterized by the diameter and the number of threads per inch. Example: 1/4”- 36 UNS has a 0.25” diameter and 36 threads per inch.
The table below shows in detail the threads, connector series and part numbers of the complete instrument cases. Additionally the model numbers of spare parts are listed, as no gauge may last forever or needs to be replaced because it was damaged by mistake.