Gages Made to ANSI/ASME B1.20.1 1983
Gaging of NPT threads is quite easy and differs from straight threads in that only one gage, an L1 plug or L1 ring is used to determine
acceptability.The taper pipe thread plug has a step at the L1 distance from its small end. When turned hand tight into the productÕs
internal pipe thread, (do not force the gage), the step is required to be flush with the large end of the product thread within a tolerance
of plus or minus one turn.
Special Note: Many times the product thread is chamfered, countersunk or recessed, exceeding the major diameter of the
thread. In these instances, the gaging point of the product thread becomes where the first visible sign of a scratch mark at the major
diameter occurs on the chamfer cone.
*NPT Master Plugs are available to check Ware on NPT Rings*