ASME B16.3 pdf download Malleable Iron Threaded Fittings Classes 150 and 300
(a) Meta! Thickness Tolerances. Metal thickness at nopoint in the castings shall be less than 90% of the valuegiven in the tables.
(b) Center-fo-End Tolerances. Permitted tolerances onthe center-to-end dimensions of the fittings are shownin Tables 2 and I-2. Tolerances for end-to-end dimensionsand lengths of couplings and reducers shall be twicethose given. The largest opening in a reducing fittinggoverns the tolerances to be applied to all openingsThese tolerances do not apply to return bends and caps
7.1 Types of Threads
All fittings shall be threaded according to ASMEB1.20.1 and shall have taper threads, except wroughtcouplings (Tables 8 and 1-8) and wrought caps (Tables9 and I-9) in NPS , and %, which may have straightthreads.
Variations in taper threading shallbe limited to oneturn large or one turn small fromgaging face onring and gaging notch on plug whenworkinggages. The variations in straight threading shall be limited to one and one-half turns large or smallfromthegaging notch on plug when using a taper pipe threadworking gage. The reference point for gaging internalfittings threads depends upon the chamfer diameter.When the internal chamfer diameter exceeds the majordiameter of the internal thread, the reference point isthe last thread scratch on the chamfer cone. When theinternal chamfer diameter does not exceed the majordiameter of the internal thread, the reference point isthe end of the fitting. (See Fig. 2.)
7.3 Countersink or Chamfer
For the purpose of easier entrance in making a jointand for protection of the thread, all internal threads shallbe countersunk a distance of not less than one-half thepitch of the thread at an angle of approximately 45 degwith the axis of the thread; all external threads shall bechamfered at an angle of 30 deg to 45 deg with the axis.Countersinking and chamfering shall be concentric withthe threads.
7.4 Thread Length
The length of threads specified in all tables shall bemeasured to include the countersink or chamfer.
The maximum allowable variation in the alignmentof threads of all openings of threaded fittings shall be5.0 mm/m (0.06 in./ft)(0.5% slope).
The addition of ribs or lugs is permitted on threadedfittings. Where ribs are used, it is recommended thattheir thickness shall be the same as specified for metalthickness of the fitting. Right-hand couplings shall havenot more than two ribs.
8.2 Special Couplings
Right- and left-hand couplings shall have four or moreribs unless the left-hand opening is clearly marked, inwhich case the use of ribs is optional with the manufacturer.
9 PLUGS,BUSHINGS，AND LOCKNUTS
For dimensions of plugs, bushings, and locknuts tobe used in connection with Classes 150 and 300 malleableiron threaded fittings, see ASME B16.14.
10 FACE BEVEL
A bevel not exceeding 5 deg is permitted on the facesof fitting openings. Center-to-end, end-to-end, andwidth of band dimensions may include or exclude thebevel.
11.1 Malleable lron Fittings
When malleable iron fittings are zinc coated, theyshall be hot dipped in accordance with ASTM A 153 or