Machinery's Handbook, 31st Edition
BUTTRESS THREADS
2083
Table 4. American National Standard Buttress Inch Screw Threads Tolerances Class 2 (Standard Grade) and Class 3 (Precision Grade) ANSI/ASME B1.9-1973 (R2017)
Basic Major Diameter, Inch
Pitch b Increment, . p 00173 Inch
From 0.5 thru 0.7 Over 16 thru 24 Tolerance on Major Diameter of External Thread, Pitch Diameter of External and Internal Threads, and Minor Diameter of Internal Thread, Inch Class 2, Standard Grade Over 0.7 thru 1.0 Over 1.0 thru 1.5 Over 1.5 thru 2.5 Over 2.5 thru 4 Over 4 thru 6 Over 6 thru 10 Over 10 thru 16
Pitch, a p Inch
Thds. per Inch
20 16 12 10
0.0500 .0056 ....
....
....
....
....
.... ....
.... .... ....
.... .... ....
.00387 .00432 .00499 .00547 .00612 .00706 .00774 .00865 .00999 .01094 .01223 .01413 .01547 .01730
0.0625 .0060 .0062 .0065 .0068 .0073 ....
0.0833 .0067 .0069 .0071 .0075 .0080 .0084 ....
0.1000 .... 0.1250 .... 0.1667 .... 0.2000 .... 0.2500 .... 0.3333 ....
.0074 .0076 .0080 .0084 .0089 .0095 .0102 ....
8 6 5 4 3
.... .... .... .... .... .... .... .... .... ....
.0083 .0086 .0091 .0095 .0101 .0108 .0115 .0092 .0096 .0100 .0105 .0111 .0118 .0125
.... .... .... .... .... .... .... ....
.0103 .0107 .0112 .0117 .0124 .0132 .0112 .0116 .0121 .0127 .0134 .0141
.... .... .... .... .... ....
.... .... .... .... .... ....
.0134 .0140 .0147 .0154
2.5 0.4000 .... 2.0 0.5000 .... 1.5 0.6667 .... 1.25 0.8000 .... 1.0 1.0000 ....
.... .... .... .... ....
.0149 .0156 .0164 .0162 .0169 .0177
.... .... ....
.0188 .0196 .0202 .0209
....
.0227
Diameter Increment, c . D 0002 3
.00169 .00189 .00215 .00252 .00296 .00342 .00400 .00470 .00543
Class 3, Precision Grade
20 16 12 10
0.0500 .0037 ....
....
....
....
....
.... ....
.... .... ....
.... .... ....
0.0625 .0040 .0042 .0043 .0046 .0049 ....
0.0833 .0044 .0046 .0048 .0050 .0053 .0056 ....
0.1000 .... 0.1250 .... 0.1667 .... .02000 .... 0.2500 .... .03333 ....
.0049 .0051 .0053 .0056 .0059 .0063 .0068 ....
8 6 5 4 3
.... .... .... .... .... .... .... .... .... ....
.0055 .0058 .0061 .0064 .0067 .0072 .0077 .0061 .0064 .0067 .0070 .0074 .0078 .0083
.... .... .... .... .... .... .... ....
.0068 .0071 .0074 .0078 .0083 .0088 .0074 .0077 .0080 .0084 .0089 .0094
.... .... .... .... .... ....
.... .... .... .... .... ....
.0089 .0093 .0098 .0103
2.5 0.4000 .... 2.0 0.5000 .... 1.5 0.6667 .... 1.25 0.8000 ....
.... .... .... .... ....
.0100 .0104 .0109 .0108 .0113 .0118
.... .... ....
.0126 .0130 .0135 .0139
1.0 1.0000 .... .0152 a For threads with pitches not shown in this table, pitch increment to be used in tolerance formula is to be determined by use of formula . . . D L p 0002 000278 000854 PD Tolerance e 3 = + + , .... where: D = basic major diameter of external thread (assuming no allowance), L e = length of engagement, and p = pitch of thread. This formula relates specifically to Class 2 (standard grade) PD tolerances. Class 3 (precision grade) PD tolerances are two-thirds of Class 2 PD tolerances. See text b When the length of engagement is taken as 10p, the formula reduces to: . . D p 0002 00173 3 + . . 3 c Diameter D , used in diameter increment formula, is based on the average of the range.
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