EXTERNAL THREAD DIMENSIONS
for MACHINE SCREWS

Machine Screw Images


External Threads for Machine Screws and SEMS
ASME B 1.1

Nominal Size &
Threads per Inch
Series
Designation
Allowance Major Diameter Pitch Diameter Stress
Area in2
Tensile
Strength*,
lb., min
Max Min Max Min Tolerance
0-80   0.060 UNF .0005 .0595 .0563 .0514 .0496 .0018 - -
1-64   0.073 UNC .0006 .0724 .0686 .0623 .0603 .0020 - -
2-56   0.086 UNC .0006 .0854 .0813 .0738 .0717 .0021 - -
3-48   0.099 UNC .0007 .0983 .0938 .0848 .0825 .0023 - -
4-40   0.112 UNC .0008 .1112 .1061 .0950 .0925 .0025 0.00604 360
5-40   0.125 UNC .0008 .1242 .1191 .1080 .1054 .0026 0.00796 470
6-32   0.138 UNC .0008 .1372 .1312 .1169 .1141 .0028 0.00909 550
8-32   0.164 UNC .0009 .1631 .1571 .1428 .1399 .0029 0.0140 850
10-24   0.190 UNC .0010 .1890 .1818 .1619 .1586 .0033 0.0175 1050
10-32   0.190 UNF .0009 .1891 .1831 .1688 .1658 .0030 0.0100 1200
12-24   0.216 UNC .0010 .2150 .2078 .1879 .1845 .0034 0.0242 1450
1/4-20   0.250 UNC .0011 .2489 .2408 .2164 .2127 .0037 0.0318 1900
1/4-28   .250 UNF .0010 .2490 .2425 .2258 .2225 .0033 0.0364 2200
5/16-18   0.312 UNC .0012 .3113 .3026 .2752 .2712 .0040 0.0524 3150
3/8-16   0.375 UNC .0013 .3737 .3643 .3331 .3287 .0044 0.0775 4650
1/2-13   0.500 UNC .0015 .4985 .4876 .4485 .4435 .0050 0.1419 8500
* Tensile strength values are based on 60,000 psi and apply to carbon steel screws and SEMS only. Hex and Hex Washer head machine screws of sufficient length may be wedge tested. Other head styles may be axial tensile tested.
The length of a flathead screw is always measured from the top of the head.


Nominal Screw Length

Tolerance on
Length

L
Nominal
Screw Size
Up to 1/2 in, incl. Over 1/2 to 1 in, incl. Over 1 to 2 in., incl. Over 2 in.
0 thru 12 -0.02 -0.03 -0.06 -0.09
1/4 thru 3/4 -0.03 -0.03 -0.06 -0.09



Thread Gaging Notes, Mechanical & Performance,
and Mechanical & Performance with Free-Spinning Lockwashers




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