Machinery's Handbook, 31st Edition
1980
Unified Screw Threads Table 4c. Extra-Fine-Thread Series, UNEF and UNREF—Basic Dimensions
Minor Diameter
Lead Angle λ at Basic P.D.
Area of Minor Dia. at D − 2 h b 0.0242 0.0344 0.0581 0.0878 0.1201 0.162 0.203 0.256 0.315 0.369 0.439 0.515
Basic Pitch Dia., a D 2 Inches
Basic Major Dia., D Inches 0.2160 0.2500 0.3125 0.3750 0.4375 0.5000 0.5625 0.6250 0.6875 0.7500 0.8125 0.8750 0.9375 1.0000 1.0625 1.1250 1.1875 1.2500 1.3125 1.3750 1.4375 1.5000 1.5625 1.6250 1.6875
Int. Thds., d D 1
Ext. Thds., c d 3 (Ref.)
Tensile Stress Area b Sq. In. 0.0270 0.0379 0.0625 0.0932 0.1274 0.170
Thds. per Inch, n
Sizes No. or Inches
Inches
Inches Deg. Min Sq. In.
12 (0.216) e
32 32 32 32 28 28 24 24 24 20 20 20 20 20 18 18 18 18 18 18 18 18 18 18 18
0.1957 0.1788 0.1822 0.2297 0.2128 0.2162 0.2922 0.2753 0.2787 0.3547 0.3378 0.3412 0.4143 0.3949 0.3988 0.4768 0.4574 0.4613 0.5354 0.5129 0.5174 0.5979 0.5754 0.5799 0.6604 0.6379 0.6424 0.7175 0.6905 0.6959 0.7800 0.7530 0.7584 0.8425 0.8155 0.8209 0.9050 0.8780 0.8834
2 2 1
55 29 57
1 ∕ 4
5 ∕ 16
1 36 1 34 1 22
3 ∕ 8
7 ∕ 16
1 ∕ 2
1
25
0.214 0.268 0.329 0.386 0.458 0.536 0.620 0.711 0.799 0.901 1.009 1.123 1.244 1.370 1.503 1.64
9 ∕ 16
1 16
5 ∕ 8
1
9
e
11 ∕ 16
1 16
3 ∕ 4
1 1 1
10
e
13 ∕ 16
5 0
7 ∕ 8
0.598 0.687 0.770 0.871 0.977 1.090 1.208 1.333 1.464 1.60 1.74 1.89 2.05
e
15 ∕ 16
1
0.9675 0.9405 0.9459 0 57 1.0264 0.9964 1.0024 0 59 1.0889 1.0589 1.0649 0 56
e
1 1 ∕ 16 1 1 ∕ 8 1 3 ∕ 16 1 1 ∕ 4
1.1514
1.1214
1.1274 0 53
e
1.2139 1.1839 1.1899 0 50
1.2764
1.2464
1.2524 0 48
e
1 5 ∕ 16 1 3 ∕ 8 1 7 ∕ 16 1 1 ∕ 2 1 9 ∕ 16 1 5 ∕ 8
1.3389 1.3089 1.3149 0 45
1.4014 1.3714 1.3774 0 1.4639 1.4339 1.4399 0
43 42
e
1.5264 1.4964 1.5024 0 40 1.5889 1.5589 1.5649 0 38
1.79 1.94 2.10
e
1.6514
1.6214
1.6274 0 37
e
1 11 ∕ 16
a British: Effective Diameter. b See formula, pages 1660 and 1668. c Design form for UNR threads. (See figure on page 1948.) d Basic minor diameter. e Secondary sizes.
Other Threads of Special Diameters, Pitches, and Lengths of Engagement: Thread data for special combinations of diameter, pitch, and length of engagement not included in selected combinations are also given in the Standard but are not given here. Also, when design considerations require non-standard pitches or extreme conditions of engagement not covered by the tables, the allowance and tolerances should be derived from the formu las in the Standard. The thread symbol for such special threads is UNS. Constant Pitch Series.— The various constant-pitch series, UN, with 4, 6, 8, 12, 16, 20, 28 and 32 threads per inch, given in Table 3 , offer a comprehensive range of diameter-pitch combinations for those purposes where the threads in the Coarse, Fine, and Extra-Fine series do not meet the particular requirements of the design. When selecting threads from these constant-pitch series, preference should be given wherever possible to those tabulated in the 8-, 12-, or 16-thread series. 8-Thread Series: The 8-thread series (8-UN) is a uniform-pitch series for large diame ters. Although originally intended for high-pressure-joint bolts and nuts, it is now widely used as a substitute for the Coarse-Thread Series for diameters larger than 1 inch.
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