Threads and Threading - Sportpilot.info

Machinery's Handbook 27th Edition
1764 UNIFIED SCREW THREADS
and mating internal threads equals or exceeds the tensile load carrying capacity of the
externally threaded member (see page 1510). It is also used where the length of engagement
is short, where a smaller lead angle is desired, where the wall thickness demands a
fine pitch, or where finer adjustment is needed.
Table 4b. Fine-Thread Series, UNF and UNRF — 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.
0 (0.060) 0.0600 80 0.0519 0.0451 0.0465 4 23 0.00151 0.00180
1 (0.073) e 0.0730 72 0.0640 0.0565 0.0580 3 57 0.00237 0.00278
2 (0.086) 0.0860 64 0.0759 0.0674 0.0691 3 45 0.00339 0.00394
3 (0.099) e 0.0990 56 0.0874 0.0778 0.0797 3 43 0.00451 0.00523
4 (0.112) 0.1120 48 0.0985 0.0871 0.0894 3 51 0.00566 0.00661
5 (0.125) 0.1250 44 0.1102 0.0979 0.1004 3 45 0.00716 0.00830
6 (0.138) 0.1380 40 0.1218 0.1082 0.1109 3 44 0.00874 0.01015
8 (0.164) 0.1640 36 0.1460 0.1309 0.1339 3 28 0.01285 0.01474
10 (0.190) 0.1900 32 0.1697 0.1528 0.1562 3 21 0.0175 0.0200
12 (0.216) e 0.2160 28 0.1928 0.1734 0.1773 3 22 0.0226 0.258
1
⁄4 0.2500 28 0.2268 0.2074 0.2113 2 52 0.0326 0.0364
5
⁄16 0.3125 24 0.2854 0.2629 0.2674 2 40 0.0524 0.0580
3
⁄8 0.3750 24 0.3479 0.3254 0.3299 2 11 0.0809 0.0878
7
⁄16 0.4375 20 0.4050 0.3780 0.3834 2 15 0.1090 0.1187
1
⁄2 0.5000 20 0.4675 0.4405 0.4459 1 57 0.1486 0.1599
9
⁄16 0.5625 18 0.5264 0.4964 0.5024 1 55 0.189 0.203
5
⁄8 0.6250 18 0.5889 0.5589 0.5649 1 43 0.240 0.256
3
⁄4 0.7500 16 0.7094 0.6763 0.6823 1 36 0.351 0.373
7
⁄8 0.8750 14 0.8286 0.7900 0.7977 1 34 0.480 0.509
1 1.0000 12 0.9459 0.9001 0.9098 1 36 0.625 0.663
11 ⁄ 8 1.1250 12 1.0709 1.0258 1.0348 1 25 0.812 0.856
11 ⁄ 4 1.2500 12 1.1959 1.1508 1.1598 1 16 1.024 1.073
13 ⁄ 8 1.3750 12 1.3209 1.2758 1.2848 1 9 1.260 1.315
11 ⁄ 2 1.5000 12 1.4459 1.4008 1.4098 1 3 1.521 1.581
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.
Extra-Fine-Thread Series: This series, UNEF/UNREF, is applicable where even finer
pitches of threads are desirable, as for short lengths of engagement and for thin-walled
tubes, nuts, ferrules, or couplings. It is also generally applicable under the conditions stated
above for the fine threads. See Table 4c.
Fine Threads for Thin-Wall Tubing: Dimensions for a 27-thread series, ranging from 1 ⁄ 4to
1-inch nominal size, also are included in Table 3. These threads are recommended for
general use on thin-wall tubing. The minimum length of complete thread is one-third of the
basic major diameter plus 5 threads (+ 0.185 in.).
Selected Combinations: Thread data are tabulated in Table 3 for certain additional
selected special combinations of diameter and pitch, with pitch diameter tolerances based
on a length of thread engagement of 9 times the pitch. The pitch diameter limits are applicable
to a length of engagement of from 5 to 15 times the pitch. (This provision should not
be confused with the lengths of thread on mating parts, as they may exceed the length of
engagement by a considerable amount.) Thread symbols are UNS and UNRS.
Copyright 2004, Industrial Press, Inc., New York, NY