Table 4. Internal Inch Screw Thread Calculations for 1 ∕ Table 4. (Continued) Internal Inch Screw Thread Calculations for 1 ∕
2 -28 UNEF-2B
2 -28 UNEF-2B
Characteristic Description
Calculation
Notes
Maximum internal minor diameter ( D 1 max ) = minimum internal minor diameter ( D 1 min ) + internal minor diameter tolerance TD 1
D D TD max min 1 1 1 = +
D 1min is rounded to six decimal places
. TD P P 025 040 0 25 0 03571429 0 40 0 03571429 0 008929 0 000510 0 008419 0 003127 1 2 2 # # = − = − = − = = . . . . . . . . . . . D D TD 0 461338 0 008419 0 469757 0 470 max min 1 1 1 = + = + = = . .
TD 1 is rounded to four decimal places
Internal minor diameter tolerance TD 1
For the Class 2B thread D 1 max is rounded to three decimal places to obtain final values. Other sizes and classes are expressed in four decimal places
Maximum internal minor diameter ( D 1 max )
Minimum internal pitch diameter ( D 2 min ) = basic major diameter ( D bsc ) − twice the external thread addendum ( h b )
D D h min bsc b 2 = −
h b = external thread addendum
. P 0 64951905 0 64951905 0 03571429 0 02319711 0 023197 b # = = = = . . . .
h
External thread addendum ( h b )
h b is rounded to six decimal places
. . D D h 0 5000 0 023197 0 476803 0 4768 min bsc b 2 = − = − = = . .
Minimum internal pitch diameter ( D 2 min ) Maximum internal pitch diameter ( D 2 max ) = minimum internal pitch diameter ( D 2 min ) + internal pitch diameter tolerance (TD 2 )
D 2 min is rounded to four decimal places
D D TD max min 2 2 2 = +
TD 2 = external pitch diameter tolerance
Constant 1.30 is for this Class 2B example, and will be different for Classes 1B and 3B. Td 2 for Class 2A (see Table 3) is rounded to six decimal places. TD 2 is rounded to four places D 2 max is rounded to four decimal places
=
. Td 130 # ^
for Class 2A h
=
. 130 0 003668 . #
TD
2
2
External pitch diameter tolerance TD 2
=
. 0 0047684 0 0048 . =
Maximum internal pitch diameter ( D 2 max )
. . D D TD 0 4768 0 0048 0 4816 max min 2 2 2 = + = + = .
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