ASME B16.4:1998 pdf free download

ASME B16.4:1998 pdf free download.GRAY AND THREADED FITTINGS.
(c) It is recognized that sortie variations are absolutely unavoidable in the making of patterns and castings. The following tolerances shall he permitted.
(1) Metal Thickness Tolerances. Metal thickness at no point in the castings shall be less than 901 of thc value givcn in Tables 3 through 7.
(2) Center-go-End Tolerances. Permitted tolerances on the center-to-end dimensions of the fittings are shown in Table 2. Tolerances for end-to-end dimensions and lengths of couplings and reducers shall be twice those given. The largest opening in a reducing fitting governs the tolerances to be applied to all openings. Thcsc tolerances do not apply to return bends and caps.
7 THREADING
(a) All flttings shall be threaded according to ASME B 1.20.1, Pipe Threads. General Purpose (Inch), and the variations in threading shall be limited to one turn large or one turn small from the gaging notch on the plug when using working gages.
(b) The reference point for gaging internal fittings threads depends upon the chamfer diameter. When the internal chamfer diameter exceeds the major diameter of the internal thread, the reference point is the last thread scratch on the chamfer cone. When the internal chamfer diameter does not exceed the major diameter of the internal thread. the retcrence point is the end of the fitting (see Fig. 2).
(c) For the purpose of easier entrance in making a joint and for protection of the thread, all threads shall be countersunk a distance of not less than one-half the pitch of the thread at an angle of approximately 45deg with the axis of the thread. Countersinking shallbe concentric with the threads.
(d )The length of the threads specified in all tablesshall be measured to include the countersink.
(e)The maximum allowable variation in the align-ment of threads of all openings of threaded fittingsshall be 0.06 in./ft (O.5%o).
8 RIBS
fa)The addition of ribs or lugs. is permitted onthreaded fittings. Where ribs are used, it is recommendedthat their thickness shall be the same as specified formetal thickness of the. fitting.
(b) Right-hand couplings shall have not more thantwo ribs.
(c)Right- and left-hand couplings shall have fouror more ribs unless the left-hand opening. is clearlymarked“L,” in which case the use of ribs is optionalwith the manufacturer.