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Screws, Fasteners, and the Design of Nonpermanent Joints 413
Table 8–2

Diameters and Area of Unified Screw Threads UNC and UNF*

Coarse Series—UNC Fine Series—UNF
Nominal Tensile- Minor- Tensile- Minor-
Major Threads Stress Diameter Threads Stress Diameter
Size Diameter per Inch Area A t Area A r per Inch Area A t Area A r
Designation in N in 2 in 2 N in 2 in 2
0 0.0600 80 0.001 80 0.001 51
1 0.0730 64 0.002 63 0.002 18 72 0.002 78 0.002 37
2 0.0860 56 0.003 70 0.003 10 64 0.003 94 0.003 39
3 0.0990 48 0.004 87 0.004 06 56 0.005 23 0.004 51
4 0.1120 40 0.006 04 0.004 96 48 0.006 61 0.005 66
5 0.1250 40 0.007 96 0.006 72 44 0.008 80 0.007 16
6 0.1380 32 0.009 09 0.007 45 40 0.010 15 0.008 74
8 0.1640 32 0.014 0 0.011 96 36 0.014 74 0.012 85
10 0.1900 24 0.017 5 0.014 50 32 0.020 0 0.017 5
12 0.2160 24 0.024 2 0.020 6 28 0.025 8 0.022 6
1 0.2500 20 0.031 8 0.026 9 28 0.036 4 0.032 6
4
5 0.3125 18 0.052 4 0.045 4 24 0.058 0 0.052 4
16
3 0.3750 16 0.077 5 0.067 8 24 0.087 8 0.080 9
8
7 0.4375 14 0.106 3 0.093 3 20 0.118 7 0.109 0
16
1 0.5000 13 0.141 9 0.125 7 20 0.159 9 0.148 6
2
9 0.5625 12 0.182 0.162 18 0.203 0.189
16
5 0.6250 11 0.226 0.202 18 0.256 0.240
8
3 0.7500 10 0.334 0.302 16 0.373 0.351
4
7 0.8750 9 0.462 0.419 14 0.509 0.480
8
1 1.0000 8 0.606 0.551 12 0.663 0.625
1 1 1.2500 7 0.969 0.890 12 1.073 1.024
4
1 1 1.5000 6 1.405 1.294 12 1.581 1.521
2
*This table was compiled from ANSI B1.1-1974. The minor diameter was found from the equation d r = d − 1.299 038p, and the pitch diameter
from d p = d − 0.649 519p. The mean of the pitch diameter and the minor diameter was used to compute the tensile-stress area.

Figure 8–3 p p
p p
(a) Square thread; (b) Acme 2 29° 2
thread. p p
2 2

d d
d r d r

(a) (b)