Abstract： ASME B16.3:2011 pdf download.Malleable Iron Threaded Fittings Classes 150 and 300. 8 THREADING 8.1 Types of Threads All fittings shall he threaded according to ANSI /ASME Bl.20.1, and shall have taper threads, except wrought couplings (Tabl...

ASME B16.3:2011 pdf download.Malleable Iron Threaded Fittings Classes 150 and 300.

8 THREADING

8.1 Types of Threads

All fittings shall he threaded according to ANSI /ASME Bl.20.1, and shall have taper threads, except wrought

couplings (Tables 8 and 1-8) and wrought caps (Tables 9 and 1-9) in NPS , and which may have straight threads.

8.2 Tolerances

Variations in taper threading shall be limited to one turn large or one turn small from the gaging face on ring

and gaging notch on plug when using working gages. The variations in straight threading shall be limited to one

and one-half turns large or small from the gaging notch on plug when using a taper pipe thread working gage. 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

reference point is the end of the fitting (see Fig. 2).

8.3 Countersink or Chamfer

For the purpose of easier entrance in making a joint and for protection of the thread, all internal threads shall be countersunk a distance of not less than one-half the pitch of the thread at an angle of approximately 45 deg

with the axis of the thread; all external threads shall be chamfered at an angle of 30 deg to 45 deg with the

axis. Countersinking and chamfering shall be concentric with the threads.

8.4 Thread Length

The length of threads specified in all tables shall be measLlred to include the countersink or chamfers

8.5 Alignment

The maximum allowable variation in the alignment of threads of all openings of threaded fittings shall be 5.0 mm/m (0.06 in./ft) (0.5% slope).

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