Threads and Threading - Sportpilot.info

Machinery's Handbook 27th Edition
1766 UNIFIED SCREW THREADS
12-Thread Series: The 12-thread series (12-UN) is a uniform pitch series for large diameters
requiring threads of medium-fine pitch. Although originally intended for boiler practice,
it is now used as a continuation of the Fine-Thread Series for diameters larger than 1 1 ⁄ 2
inches.
16-Thread Series: The 16-thread series (16-UN) is a uniform pitch series for large diameters
requiring fine-pitch threads. It is suitable for adjusting collars and retaining nuts, and
also serves as a continuation of the Extra-fine Thread Series for diameters larger than 1 11 ⁄ 16
inches.
4-, 6-, 20-, 28-, and 32-Thread Series: These thread series have been used more or less
widely in industry for various applications where the Standard Coarse, Fine or Extra-fine
Series were not as applicable. They are now recognized as Standard Unified Thread Series
in a specified selection of diameters for each pitch (see Table 2).
Whenever a thread in a constant-pitch series also appears in the UNC, UNF, or UNEF
series, the symbols and tolerances for limits of size of UNC, UNF, or UNEF series are
applicable, as will be seen in Tables 2 and 3.
Table 5a. 4–Thread Series, 4–UN and 4–UNR — Basic Dimensions
Sizes
Basic
Major
Dia.,
D
Basic
Pitch
Dia., a
D2 Minor Diameter
Lead
Angle λ
at Basic
P.D.
Area of
Minor
Dia. at
D − 2hb Tensile
Stress
Areab Primary Secondary
Ext.
Thds., c
Int.
Thds.,
d3s (Ref.)
d
D1 Inches Inches Inches Inches Inches Inches Deg. Min. Sq. In. Sq. In.
21 ⁄ e
2 2.5000 2.3376 2.2023 2.2294 1 57 3.72 4.00
25 ⁄ 8 2.6250 2.4626 2.3273 2.3544 1 51 4.16 4.45
23 ⁄ e
4 2.7500 2.5876 2.4523 2.4794 1 46 4.62 4.93
27 ⁄ 8 2.8750 2.7126 2.5773 2.6044 1 41 5.11 5.44
3e 3.0000 2.8376 2.7023 2.7294 1 36 5.62 5.97
31 ⁄ 8 3.1250 2.9626 2.8273 2.8544 1 32 6.16 6.52
31 ⁄ e
4 3.2500 3.0876 2.9523 2.9794 1 29 6.72 7.10
33 ⁄ 8 3.3750 3.2126 3.0773 3.1044 1 25 7.31 7.70
31 ⁄ e
2 3.5000 3.3376 3.2023 3.2294 1 22 7.92 8.33
35 ⁄ 8 3.6250 3.4626 3.3273 3.3544 1 19 8.55 9.00
31 ⁄ e
4 3.7500 3.5876 3.4523 3.4794 1 16 9.21 9.66
37 ⁄ 8 3.8750 3.7126 3.5773 3.6044 1 14 9.90 10.36
4e 4.0000 3.8376 3.7023 3.7294 1 11 10.61 11.08
41 ⁄ 8 4.1250 3.9626 3.8273 3.8544 1 9 11.34 11.83
41 ⁄ 4 4.2500 4.0876 3.9523 3.9794 1 7 12.10 12.61
43 ⁄ 8 4.3750 4.2126 4.0773 4.1044 1 5 12.88 13.41
41 ⁄ 2 4.5000 4.3376 4.2023 4.2294 1 3 13.69 14.23
45 ⁄ 8 4.6250 4.4626 4.3273 4.3544 1 1 14.52 15.1
43 ⁄ 4 4.7500 4.5876 4.4523 4.4794 1 0 15.4 15.9
47 ⁄ 8 4.8750 4.7126 4.5773 4.6044 0 58 16.3 16.8
5 5.0000 4.8376 4.7023 4.7294 0 57 17.2 17.8
51 ⁄ 8 5.1250 4.9626 4.8273 4.8544 0 55 18.1 18.7
51 ⁄ 4 5.2500 5.0876 4.9523 4.9794 0 54 19.1 19.7
53 ⁄ 8 5.3750 5.2126 5.0773 5.1044 0 52 20.0 20.7
51 ⁄ 2 5.5000 5.3376 5.2023 5.2294 0 51 21.0 21.7
55 ⁄ 8 5.6250 5.4626 5.3273 5.3544 0 50 22.1 22.7
53 ⁄ 4 5.7500 5.5876 5.4523 5.4794 0 49 23.1 23.8
57 ⁄ 8 5.8750 5.7126 5.5773 5.6044 0 48 24.2 24.9
6 6.0000 5.8376 5.7023 5.7294 0 47 25.3 26.0
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 These are standard sizes of the UNC series.
Copyright 2004, Industrial Press, Inc., New York, NY