ASME B1.20.2M-2006 pdf free download.Pipe Threads,60 deg, eneral Purpose.
gauge and a taper-threaded ring gauge. See Figs. 4 and 5. The plug gauges are made to dimensions given in Table 5 with a gauging notch located a distance L1 from the small end. The L1 ring gauge has a length equal to dimension L1. The roots of the threads on these gauges shall clear O,0381P width. A sharp V or undercut clearance is acceptable.
The crests are to be truncated an amount equal to 0,140P for 27 threads per 25,4 mm; 0,109P for 18 threads per 25,4 mm; 0,100P for 14 threads per 25,4 mm; 111/2 threads per 25,4 mm; and 8 threads per 25,4 mm threads (see Fig. 5).
It is noted that these gauges are truncated at the crests and cleared at the roots, so that they bear only on the flanks of the thread. Thus, they do not check the root truncations or crest truncations specified in Table 1. When it is deemed necessary to determine whether or not such truncations are within the specified limits, it is necessary to make further inspection. For this purpose, inspection by optical projection is suggested.
Partial end threads shall be removed on both ends of the ring gauge and on the small end of the plug gauge to full form profile in order to avoid possible seating error from bent or malformed feathered edges.
6.1.2 Marking of Gauges. Each gauge shall be marked so as to indicate clearly the nominal size of pipe; threads per 25,4 mm; and series designation “NPT.”
6.2 Classes of Gauges
Gauges of the following types may be used to completely cover gauge requirements:
(a) master gauges used to check working gauges
(b) working gauges used to check threads during manufacture and for conformance inspection
6.2.1 Master Gauges. The set of master gauges consists of an L1 taper-threaded plug gauge and an L1 taper-threaded ring gauge (see Figs. 4 and 5). The plug gauge is made to dimensions specified in Table 5. It is constructed of hardened steel with a gauging notch located a distance L1 (see Table 2) from the small end. The ring gauge has a length equal to dimension L1 specified in Table 5. This ring is fitted to its mating plug, seating flush at the notch within ±0,051 mm for sizes 1/16 to 2 inclusive; ±0,076 mm for sizes 2’/2 to 12 inclusive; and within ±0,127 mm for size 14 and larger. The roots of the threads on these ring gauges shall clear a 0,0381P flat or may be undercut beyond a sharp V. The crests of the plug and ring gauge are truncated 0,100P. The set of master gauges is used for checking working gauges (see para. 6.3.2). A supplementary check by optical means should be made of flank angle and form.
CAUTION: It should be understood that only a specifically matched set of master gauges (L1 plug and L1 ring) can be expected to mate with each other within the tolerance specified. There are many characteristics or variations in gauge elements that may combine to cause a significant standoff difference between master gauges which are not specifically matched.
6.2.2 Working Gauges. Each set of working gauges consists of an L1 taper-threaded ring gauge and an L1 taper-threaded plug gauge and is used for checking the product. These gauges are made of hardened steel or equivalent material to dimensions given in Table 5 (see para. 6.3.2 for tolerance). In locating the basic notch of the plug gauge, the plane of the notch should intersect the crest of the thread.
6.3 Gauge Tolerances
In the manufacture of gauges, variations from basic dimensions are unavoidable. Furthermore, gauges will wear in use. In order to fix the maximum allowable variations of gauges, tolerances have been established. See Table 6 and para. 6.3.2.
6.3.1 Master Gauge Tolerances. The set of master gauges should be made to the basic dimensions as accurately as possible, but in no case shall the cumulative variation exceed one-half of the total cumulative tolerance in Columns 13 and 14 of Table 6. Each master gauge should be accompanied by a record of the measurement of all elements of the thread and the standoff of master plug to master ring (large end of ring gauge to basic notch of plug gauge).
6.3.2 Working Gauge Tolerance. All gauges applied to the product thread, whether in manufacture or inspection, are designated as working gauges.