ASME B16.15:2006 pdf download.Cast Copper Alloy Threaded Fittings.
6.2 Tolerances
The permissible tolerance 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 gaging notch on plug, when using 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.
6.3 Countersink or Chamfer
All internal threads shall not be countersunk a distance of less than one-half the pitch of the thread at an angle of approximately 45 deg with the axis of the thread, and all external threads shall be chamfered at an angle of 30 deg to 45 deg with the axis, both for the purpose of easier entrance in making a joint, and for protection of the thread. Countersinking and chamfering shall be concentric with the threads.
6.4 Length of Thread
The length of threads specified in all tables shall be measured to include the countersink or chamfer.
6.5 Alignment
The maximum allowable variation in the alignment of threads of all openings of threaded pipe fittings shall be 1 mm/m (0.06 in/ft) or 0.5%.
The permissible tolerance 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 gaging notch on plug, when using 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.
6.3 Countersink or Chamfer
All internal threads shall not be countersunk a distance of less than one-half the pitch of the thread at an angle of approximately 45 deg with the axis of the thread, and all external threads shall be chamfered at an angle of 30 deg to 45 deg with the axis, both for the purpose of easier entrance in making a joint, and for protection of the thread. Countersinking and chamfering shall be concentric with the threads.
6.4 Length of Thread
The length of threads specified in all tables shall be measured to include the countersink or chamfer.
6.5 Alignment
The maximum allowable variation in the alignment of threads of all openings of threaded pipe fittings shall be 1 mm/m (0.06 in/ft) or 0.5%.
