ANPT 6-Step Plug Gage 3/8-18
WESTport provides a complete range of Aeronautical National Form Taper Pipe Thread Plug Gages per SAE AS71051. ANPT thread plug gages are intended for use on pipe, plugs, fittings, and similar devices in aeronautical components and equipment requiring a sealed thread joint and where straight threads and gaskets or O-rings are inadequate.
Other standards referenced are MIL-G-10944 - Gages, Dimensional Control and AND10052 - Bosses - Standard Dimensions for External Pipe Thread. Inspection gages shall not be used when worn beyond the basic dimensions by more than a ‚àö√á¬¨Œ© turn or pitch. In the case of internal threads, proper allowance shall be made for any variation from basic when using a gage L1 and L3.
Thread plug gages may be used, having three gaging notches, basic, maximum, and minimum, representing the tolerance of plus or minus one turn, the maximum notch being one turn below basic and all three notches equally spaced around the gage diameter. If requirements exists for external or internal threads to be chamfered or countersunk in excess of the dimensions in table 1 of the standard, then the thread size should be determined by using as the reference point, the end of the chamfer or bottom of the countersink (first thread scratch) instead of from the end of the pipe or fitting.
WESTport Gage Corporation provides a Certificate of Accuracy, traceable to NIST (National Institute of Standards and Technology), free of charge with every gage.