An internal Thread Comparator is an ideal way to inspect the functional diameter of internal threads and collect actual measurement values as opposed to fix limit Go and No Go gaging. The ITC reads the actual size of the  pitch diameter showing its position in relation to the high and low allowable limits.. The ITC reduces gaging time compared to Go and No Go gaging. The ITC method of inspection can assist in meeting the requirements of product acceptability in accordance with SYSTEM 21, SYSTEM 22 and SYSTEM 23. When setting the ITC - DO NOT ROTATE THE MASTER RING GAGE OR THE PART ON THE SEGMENTS AS THIS COULD CAUSE DAMAGE AND WEAR TO THE GAGE AND OR SEGMENTS.  Erroneous readings may result from rotating the gage or the part due to the helical pull of the thread path. https://www.threadcheck.com/tri-roll-thread-comparator.asp?pcFilter=itc-comparator-and-gaging-segments-products   [caption id="attachment_282" align="alignleft" width="197"] ITC - Internal Thread Comparator[/caption]