Machinery's Handbook, 31st Edition
Thread Gages 2147 Table 5. Formulas for Limits of American National Standard Gages for Unified Inch Screw Threads ANSI/ASME B1.2-1983 (R2017) No. Thread Gages for External Threads 1 GO Pitch Diameter = Maximum pitch diameter of external thread. Gage tolerance is minus. 2 GO Minor Diameter = Maximum pitch diameter of external thread minus H /2. Gage tolerance is minus. 3 NOT GO (LO) Pitch Diameter (for plus tolerance gage) = Minimum pitch diameter of external thread. Gage tolerance is plus. 4 NOT GO (LO) Minor Diameter = Minimum pitch diameter of external thread minus H /4. Gage tolerance is plus. Plain Gages for Major Diameter of External Threads 5 GO = Maximum major diameter of external thread. Gage tolerance is minus. 6 NOT GO = Minimum major diameter of external thread. Gage tolerance is plus. Thread Gages for Internal Threads 7 GO Major Diameter = Minimum major diameter of internal thread. Gage tolerance is plus. 8 GO Pitch Diameter = Minimum pitch diameter of internal thread. Gage tolerance is plus. 9 NOT GO (HI) Major Diameter = Maximum pitch diameter of internal thread plus H /2. Gage tolerance is minus. 10 NOT GO (HI) Pitch Diameter = Maximum pitch diameter of internal thread. Gage tolerance is minus. Plain Gages for Minor Diameter of Internal Threads 11 GO = Minimum minor diameter of internal thread. Gage tolerance is plus. 12 NOT GO = Maximum minor diameter of internal thread. Gage tolerance is minus. Full Form nd Truncated Setting Plugs 13 GO Major Diameter (Truncated Portion) = Maximum major diameter of external thread (= minimum major diameter of full portion of GO setting plug) minus . . p p 0060 0017 3 2 + _ i . Gage tolerance is minus. 14 GO Major Diameter (Full Portion) = Maximum major diameter of external thread. Gage tolerance is plus. 15 GO Pitch Diameter = Maximum pitch diameter of external thread. Gage tolerance is minus. 16 a NOT GO (LO) Major Diameter (Truncated Portion) = Minimum pitch diameter of external thread plus H /2. Gage tolerance is minus. 17 NOT GO (LO) Major Diameter (Full Portion) = Maximum major diameter of external thread provided major diameter crest width shall not be less than 0.001 in. (0.0009 in. truncation). Apply W tolerance plus for maximum size except that for 0.001 in. crest width apply tolerance minus. For the 0.001 in. crest width, major diameter is equal to maximum major diameter of external thread plus 0.216506 p minus the sum of external thread pitch diameter tolerance and 0.0017 in. 18 NOT GO (LO) Pitch Diameter = Minimum pitch diameter of external thread. Gage tolerance is plus. Solid Thread-setting Rings for Snap and Indicating Gages 19 b GO Pitch Diameter = Minimum pitch diameter of internal thread. W gage tolerance is plus. 20 GO Minor Diameter = Minimum minor diameter of internal thread. W gage tolerance is minus. 21 b NOT GO (HI) Pitch Diameter = Maximum pitch diameter of internal thread. W gage tolerance is minus. 22 NOT GO (HI) Minor Diameter = Maximum minor diameter of internal thread. W gage tolerance is minus. a Truncated portion is required when optional sharp root profile is used. b Tolerances greater than W tolerance for pitch diameter are acceptable when internal indicating or snap gage can accommodate a greater tolerance and when agreed upon by supplier and user. See data in Screw Thread Systems section for symbols and dimensions of Unified Screw Threads.
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