Machinery's Handbook, 31st Edition
1994
Miniature Screw Threads Table 3. Unified Miniature Screw Threads—Basic and Design Form Dimensions Basic Thread Form External Thread Design Form Internal Thread Design Form Threads per inch n a Pitch p Height of Sharp V H = 0.86603 p Height h b = 0.52 p Addendum h ab = h as = 0.32476 p Height h s = 0.60 p Flat at Crest F cs = 0.125 p Radius at Root r rs = 0.158 p Height h n = 0.556 p Flat at Crest F cn = 0.27456 p Radius at Root r rn = 0.072 p
Millimeter Dimensions
… .080 … .090 … .100 … .125 … .150 … .175 … .200 … .225 … .250 … .300
.0693 .0779 .0866 .1083 .1299 .1516 .1732 .1949 .2165 .2598
.0416 .0468 .0520 .0650 .0780 .0910 .1040 .1170 .1300 .1560
.0260 .0292 .0325 .0406 .0487 .0568 .0650 .0731 .0812 .0974
.048 .0100 .054 .0112 .060 .0125 .075 .0156 .090 .0188 .105 .0219 .120 .0250 .135 .0281 .150 .0312 .180 .0375
.0126 .0445 .0220 .0142 .0500 .0247 .0158 .0556 .0275 .0198 .0695 .0343 .0237 .0834 .0412 .0277 .0973 .0480 .0316 .1112 .0549 .0356 .1251 .0618 .0395 .1390 .0686 .0474 .1668 .0824
.0058 .0065 .0072 .0090 .0108 .0126 .0144 .0162 .0180 .0216
Inch Dimensions
317 1 ∕ 2 .003150 .00273 .00164 .00102 .00189 .00039 .00050 .00175 .00086 .00023 282 2 ∕ 9 .003543 .00307 .00184 .00115 .00213 .00044 .00056 .00197 .00097 .00026 254 .003937 .00341 .00205 .00128 .00236 .00049 .00062 .00219 .00108 .00028 203 1 ∕ 5 .004921 .00426 .00256 .00160 .00295 .00062 .00078 .00274 .00135 .00035 169 1 ∕ 3 .005906 .00511 .00307 .00192 .00354 .00074 .00093 .00328 .00162 .00043 145 1 ∕ 7 .006890 .00597 .00358 .00224 .00413 .00086 .00109 .00383 .00189 .00050 127 .007874 .00682 .00409 .00256 .00472 .00098 .00124 .00438 .00216 .00057 112 8 ∕ 9 .008858 .00767 .00461 .00288 .00531 .00111 .00140 .00493 .00243 .00064 101 3 ∕ 5 .009843 .00852 .00512 .00320 .00591 .00123 .00156 .00547 .00270 .00071 84 2 ∕ 3 .011811 .01023 .00614 .00384 .00709 .00148 .00187 .00657 .00324 .00085 a In Table 5 and Table 6 these values are shown rounded to the nearest whole number. Table 4. Unified Miniature Screw Threads—Formulas for Basic and Design Dimensions and Tolerances Formulas for Basic Dimensions D = Basic Major Diameter and Nominal Size in millimeters; p = Pitch in millimeters; E = Basic Pitch Diameter in millimeters = D − 0.64952 p ; and K = Basic Minor Diameter in millimeters = D − 1.04 p Formulas for Design Dimensions (Maximum Material) External Thread Internal Thread D s = Major Diameter = D D n = Major Diameter = D + 0.072 p E s = Pitch Diameter = E E n = Pitch Diameter = E K s = Minor Diameter = D − 1.20 p K n = Minor Diameter = K Formulas for Tolerances on Design Dimensions a External Thread ( − ) Internal Thread (+) Major Diameter Tol., 0.12 p + 0.006 b Major Diameter Tol., 0.168 p + 0.008 Pitch Diameter Tol., 0.08 p + 0.008 Pitch Diameter Tol., 0.08 p + 0.008 c Minor Diameter Tol., 0.16 p + 0.008 Minor Diameter Tol., 0.32 p + 0.012 a These tolerances are based on lengths of engagement of 2 ⁄ 3 D to 1 1 ⁄ 2 D . b This tolerance establishes the maximum limit of the major diameter of the internal thread. In practice, this limit is applied to the threading tool (tap) and not gaged on the product. Values for this tolerance are, therefore, not given in Table 5. c This tolerance establishes the minimum limit of the minor diameter of the external thread. In practice, this limit is applied to the threading tool and only gaged on the product in confirming new tools. Values for this tolerance are, therefore, not given in Table 5. Metric units (millimeters) apply in all formulas. Inch tolerances are not derived by direct conver sion of the metric values. They are the differences between the rounded off limits of size in inch units.
Copyright 2020, Industrial Press, Inc.
ebooks.industrialpress.com
Made with FlippingBook - Share PDF online