Tech Tip #5: Gaging Threaded Holes

To confirm the accuracy of a tapped hole, always use a Go-No Go gage. Never use a fastener (i.e.: screw, or bolt). Using a screw, or bolt will not allow you to verify size of the thread produced, but only indicate that the bolt used will fit in that particular hole. Go-No Gages can give indications as to where the thread produced is within the thread specification. A screw or bolt is not capable of giving such an indication.  Accurate gages will also help predict remaining tool life by indicating tightness or looseness of the gage in the part.