Threads and Threading - Sportpilot.info

Machinery's Handbook 27th Edition
UNIFIED SCREW THREADS 1763
Coarse-Thread Series: This series, UNC/UNRC, is the one most commonly used in the
bulk production of bolts, screws, nuts and other general engineering applications. It is also
used for threading into lower tensile strength materials such as cast iron, mild steel and
softer materials (bronze, brass, aluminum, magnesium and plastics) to obtain the optimum
resistance to stripping of the internal thread. It is applicable for rapid assembly or disassembly,
or if corrosion or slight damage is possible.
Table 4a. Coarse-Thread Series, UNC and UNRC — Basic Dimensions
Sizes
No. or
Basic
Major
Dia.,
D
Thds.
per
Inch,
Basic
Pitch
Dia.,
Inches
n
a
D2 Minor Diameter
Lead
Angle λ
at Basic
P.D.
Area of
Minor
Dia. at
D-2hb Tensile
Stress
Areab Ext.
Thds., c
Int.
Thds.,
d3 (Ref.)
d
D1 Inches Inches Inches Inches Deg. Min Sq. In. Sq. In.
1 (0.073) e 0.0730 64 0.0629 0.0544 0.0561 4 31 0.00218 0.00263
2 (0.086) 0.0860 56 0.0744 0.0648 0.0667 4 22 0.00310 0.00370
3 (0.099) e 0.0990 48 0.0855 0.0741 0.0764 4 26 0.00406 0.00487
4 (0.112) 0.1120 40 0.0958 0.0822 0.0849 4 45 0.00496 0.00604
5 (0.125) 0.1250 40 0.1088 0.0952 0.0979 4 11 0.00672 0.00796
6 (0.138) 0.1380 32 0.1177 0.1008 0.1042 4 50 0.00745 0.00909
8 (0.164) 0.1640 32 0.1437 0.1268 0.1302 3 58 0.01196 0.0140
10 (0.190) 0.1900 24 0.1629 0.1404 0.1449 4 39 0.01450 0.0175
12 (0.216) e 0.2160 24 0.1889 0.1664 0.1709 4 1 0.0206 0.0242
1
⁄4 0.2500 20 0.2175 0.1905 0.1959 4 11 0.0269 0.0318
5
⁄16 0.3125 18 0.2764 0.2464 0.2524 3 40 0.0454 0.0524
3
⁄8 0.3750 16 0.3344 0.3005 0.3073 3 24 0.0678 0.0775
7
⁄16 0.4375 14 0.3911 0.3525 0.3602 3 20 0.0933 0.1063
1
⁄2 0.5000 13 0.4500 0.4084 0.4167 3 7 0.1257 0.1419
9
⁄16 0.5625 12 0.5084 0.4633 0.4723 2 59 0.162 0.182
5
⁄8 0.6250 11 0.5660 0.5168 0.5266 2 56 0.202 0.226
3
⁄4 0.7500 10 0.6850 0.6309 0.6417 2 40 0.302 0.334
7
⁄8 0.8750 9 0.8028 0.7427 0.7547 2 31 0.419 0.462
1 1.0000 8 0.9188 0.8512 0.8647 2 29 0.551 0.606
11 ⁄ 8 1.1250 7 1.0322 0.9549 0.9704 2 31 0.693 0.763
11 ⁄ 4 1.2500 7 1.1572 1.0799 1.0954 2 15 0.890 0.969
13 ⁄ 8 1.3750 6 1.2667 1.1766 1.1946 2 24 1.054 1.155
11 ⁄ 2 1.5000 6 1.3917 1.3016 1.3196 2 11 1.294 1.405
13 ⁄ 4 1.7500 5 1.6201 1.5119 1.5335 2 15 1.74 1.90
2 2.0000 41 ⁄ 2 1.8557 1.7353 1.7594 2 11 2.30 2.50
21 ⁄ 4 2.2500 41 ⁄ 2 2.1057 1.9853 2.0094 1 55 3.02 3.25
21 ⁄ 2 2.5000 4 2.3376 2.2023 2.2294 1 57 3.72 4.00
23 ⁄ 4 2.7500 4 2.5876 2.4523 2.4794 1 46 4.62 4.93
3 3.0000 4 2.8376 2.7023 2.7294 1 36 5.62 5.97
31 ⁄ 4 3.2500 4 3.0876 2.9523 2.9794 1 29 6.72 7.10
31 ⁄ 4 3.500 4 3.3376 3.2023 3.2294 1 22 7.92 8.33
33 ⁄ 4 3.7500 4 3.5876 3.4523 3.4794 1 16 9.21 9.66
4 4.0000 4 3.8376 3.7023 3.7294 1 11 10.61 11.08
a British: Effective Diameter.
b See formula, pages 1502 and 1510.
c Design form for UNR threads. (See figure on page 1733.)
d Basic minor diameter.
e Secondary sizes.
Fine-Thread Series: This series, UNF/UNRF, is suitable for the production of bolts,
screws, and nuts and for other applications where the Coarse series is not applicable. External
threads of this series have greater tensile stress area than comparable sizes of the
Coarse series. The Fine series is suitable when the resistance to stripping of both external
Copyright 2004, Industrial Press, Inc., New York, NY