Machinery's Handbook, 31st Edition
2062 Centralizing Acme Screw Threads Table 5. American National Standard General Purpose Acme Single-Start Screw Threads—Pitch Diameter Tolerances ANSI/ASME B1.5-1997 (R2014)
Class of Thread
Class of Thread
2G b
2G b
3G
4G
3G
4G
Nom. Dia., a D
Nom. Dia., a D
Diameter Increment
Diameter Increment
. D 0006
. D 00028
. D 0002
. D 0006
. D 00028
. D 0002
.00300 .00335 .00367 .00397 .00424 .00474 .00520 .00561 .00600 .00636 .00671 .00704
.00140 .00157 .00171 .00185 .00198 .00221 .00242 .00262 .00280 .00297 .00313 .00328
.00100 .00112 .00122 .00132 .00141 .00158 .00173 .00187 .00200 .00212 .00224 .00235
.00735 .00794 .00849 .00900 .00949 .00995 .01039 .01122 .01200 .01273 .01342
.00343 .00370 .00396 .00420 .00443 .00464 .00485 .00524 .00560 .00594 .00626
.00245 .00265 .00283 .00300 .00316 .00332 .00346 .00374 .00400 .00424 .00447
1 1 2 2 2 2 3 3 4 4 5
1 ∕ 5 ∕ 3 ∕ 7 ∕ 1 ∕ 5 ∕ 3 ∕ 7 ∕
1 ∕ 3 ∕ 1 ∕ 1 ∕ 3 ∕
4
2 4
16
8
16
4 2 4
2 8 4 8 8 4 8
1 ∕
2
1
1 1 ∕ 1 1 ∕ 1 3 ∕
1 ∕
2
… … … …
Class of Thread
Class of Thread
Thds. per Inch, c n
Thds. per Inch c , n
2G b
2G b
3G
4G
3G
4G
Pitch Increment
Pitch Increment
. n 0030 1 .
n 0014 1 .
n 0010 1 .00250 .00267 .00289
. n 0030 1 .
n 0014 1 .
n 0010 1 .00500 .00577 .00632
16 14 12 10
.00750 .00802 .00866 .00949 .01061 .01225 .01342
.00350 .00374 .00404 .00443 .00495 .00572 .00626
4 3 2 2 1 ∕ 1 1 ∕ 1 1 ∕
.01500 .01732 .01897 .02121 .02449 .02598 .03000
.00700 .00808 .00885 .00990 .01143 .01212 .01400
2
.00316 .00354 .00408 .00447
.00707 .00816 .00866
8 6 5
2 3
1 .01000 For any particular size of thread, the pitch diameter tolerance is obtained by adding the diameter increment from the upper half of the table to the pitch increment from the lower half of the table. Example: A 1 ∕ 4 -16 Acme-2G thread has a pitch diameter tolerance of 0.00300 + 0.00750 = 0.0105 inch. The equivalent tolerance on thread thickness is 0.259 times the pitch diameter tolerance. a For a nominal diameter between any two tabulated nominal diameters, use the diameter increment for the larger of the two tabulated nominal diameters. b Columns for the 2G Class of thread in this table also apply to American National Standard Stub Acme threads, ANSI/ASME B1.8-1988 (R2016). c All other dimensions are given in inches. Application: These three classes together with the accompanying specifications are for the purpose of ensuring the interchangeable manufacture of Centralizing Acme threaded parts. Users are free to select the classes best adapted to their particular needs. It is suggested that external and internal threads of the same class be used together for centralizing assemblies, Class 2C providing the maximum end play or backlash. If less backlash or end play is desired, Classes 3C and 4C are provided. The requirement for a centralizing fit is that the sum of the major diameter tolerance plus the major diameter allowance on the internal thread, and the major diameter tolerance on the external thread shall equal or be less than the pitch diameter allowance on the external thread. A Class 2C external thread, which has a larger pitch diameter allowance than either a Class 3C or 4C, can be used interchangeably with a Class 2C, 3C, or 4C internal thread and fulfill this requirement. Similarly, a Class 3C external thread can be used interchangeably with a Class 3C or 4C internal thread, but only a Class 4C internal thread can be used with a Class 4C external thread.
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