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Setting Plug Tolerances


Sent: Friday, July 28, 2006
Subject: Setting Plug Tolerances

Dear Tech @ Vermont Gage,
I am trying to calculate the major and truncated diameter tolerances for a .8438 - 24 UNS 3A thread ring setting plug with a GO pitch diameter of .8167 and a NOGO pitch diameter of .8136.
I've tried using the formulas in ANSI / ASME B1.2-1983 but am running into a mathmatical brick wall.
Can you help me out?

Reply from Vermont Gage Technical Support

The Formulas for the Setting Plug gages may be found on page 17, Table 5. ANSI/ASME has calculated some of the values for you on page 32, Table 9. Table 9 has the values calculated for the Go Truncation in Column 3, (24 TPI = .0079). .8359 is your Go Truncated Major Diameter (.8438 -.0079 = .8359). The NoGo Truncated Major Diameter is the minimum pitch diameter plus H/2. The values for H/2 may be found in Table 9, Column 12, (24 TPI = .01804). .8316 is your NoGo Truncated Major Diameter, (.8136 + .01804 = .8316). The Go Full Form Major is .8438 +.0005 W tolerance for Major, (.0005) page 25, Table 7, Column 6. The NoGo Full Form Major is the same because the crest width is greater than .001 the NoGo tolerance is the same as the Go major tolerance.
See the Spec Sheet Here.
p.s. Please note that the pitch diameter tolerance of the set plugs is Class X, (.0003) page 18, Table 6, this is per page 154, Table 12, Note 7.
Mike Oddy