Technical Info

Thread Series

All thread rod is manufactured in three different thread series: Unified National Coarse (UNC), Unified National Fine (UNF) and 8-Thread Series (8UN).  UNC thread is the most common designation for all thread rods.  UNF thread is most often used for precision applications.  8UN thread is used specifically for grades under ASTM A193 and A320 and is used for bolts 1” in diameter and larger.

Coarse Thread Series - UNC Fine Thread Series - UNF 8-Thread Series - 8UN
Nominal Size and Threads Per In. Basic Pitch Dia. Section at Minor Dia. Tensile Stress Area Nominal Size and Threads Per In. Basic Pitch Dia. Section at Minor Dia. Tensile Stress Area Nominal Size and Threads Per In. Basic Pitch Dia. Section at Minor Dia. Tensile Stress Area
In. Sq in. Sq in. In. Sq in. Sq in. In. Sq in. Sq in.
38 - 16 0.3344 0.0678 0.0775 38 - 24 0.3479 0.0809 0.0878 --    -- -- -- --
716 - 14 0.3911 0.0933 0.1063 716 - 20 0.4050 0.1090 0.1187 --    -- -- -- --
12 - 13 0.4500 0.1257 0.1419 12 - 20 0.4675 0.1486 0.1599 --    -- -- -- --
916 - 12 0.5084 0.162 0.182 916 - 18 0.5264 0.189 0.203 --    -- -- -- --
58 - 11 0.5660 0.202 0.226 58 - 18 0.5889 0.240 0.256 --    -- -- -- --
34 - 10 0.6850 0.302 0.334 34 - 16 0.7094 0.351 0.373 --    -- -- -- --
78 - 9 0.8028 0.419 0.462 78 - 14 0.8286 0.480 0.509 --    -- -- -- --
1 - 8 0.9188 0.551 0.606 1 - 12 0.9459 0.625 0.663 1 - 8 0.9188 0.551 0.606
118 - 7 1.0322 0.693 0.763 118 - 12 1.0709 0.812 0.856 118 - 8 1.0438 0.728 0.790
114 - 7 1.1572 0.890 0.969 114 - 12 1.1959 1.024 1.073 114 - 8 1.1688 0.929 1.000
138 - 6 1.2667 1.054 1.155 138 - 12 1.3209 1.260 1.315 138 - 8 1.2938 1.155 1.233
112 - 6 1.3917 1.294 1.405 112 - 12 1.4459 1.521 1.581 112 - 8 1.4188 1.405 1.492
--    -- -- -- -- --    -- -- -- -- 158 - 8 1.5438 1.68 1.78
134 - 5 1.6201 1.74 1.90 --    -- -- -- -- 134 - 8 1.6688 1.98 2.08
--    -- -- -- -- --    -- -- -- -- 178 - 8 1.7938 2.30 2.41
2 - 412 1.8557 2.30 2.50 --    -- -- -- -- 2 - 8 1.9188 2.65 2.77
214 - 412 2.1057 3.02 3.25 --    -- -- -- -- 214 - 8 2.1688 3.42 3.56
212 - 4 2.3376 3.72 4.00 --    -- -- -- -- 212 - 8 2.4188 4.29 4.44
234 - 4 2.5876 4.62 4.93 --    -- -- -- -- 234 - 8 2.6688 5.26 5.43
3 - 4 2.8376 5.62 5.97 --    -- -- -- -- 3 - 8 2.9188 6.32 6.51
314 - 4 3.0876 6.72 7.10 --    -- -- -- -- 314 - 8 3.1688 7.49 7.69
312 - 4 3.3376 7.92 8.33 --    -- -- -- -- 312 - 8 3.4188 8.75 8.96
334 - 4 3.5876 9.21 9.66 --    -- -- -- -- 334 - 8 3.6688 10.11 10.34
4 - 4 3.8376 10.61 11.08 --    -- -- -- -- 4 - 8 3.9188 11.57 11.81

Nut Compatibility

Grade of Bolt Surface Finish Nominal Size Inches A563 Grade and ANSI Nut Style
Recommended Suitable
Hex Heavy Hex Hex Heavy Hex
Any 14 to 112
A
B,D,DH
A,B,C,D,DH,DH3
>112 to 2
A
A
C,D,DH,DH3
>2 to 4
A
C,D,DH,DH3
Any 14 to 112
A
B,D,DH
A,B,C,D,DH,DH3
>112 to 2
A
A
>2 to 4
A
Plain 14 to 112
C
D,DH
C3,D,DH,DH3
>112 to 4
C
C3,D,DH,DH3
Galvanized 14 to 112
DH
>112 to 4
DH
Plain 14 to 112
DH
DH
D,DH,DH3
>112 to 4
DH
DH3
Plain 14 to 112
B
D,DH
B,C,C3,D,DH,DH3
>112 to 3
A
C,C3,D,DH,DH3
Galvanized 14 to 112
DH
D,DH
D
>112 to 3
DH
D
A687
Plain 58 - 3
D
DH,DH3
Galvanized 58 - 3
DH
Any 12 to 112
A
B,D,DH
A,B,C,D,DH,DH3
>112 to 4
A
C,D,DH,DH3
Plain 12 to 112
A
B,D,DH
A,B,C,D,DH,DH3
>112 to 4
A
C,D,DH,DH3
Galvanized 12 to 4
A
C,D,DH,DH3
Plain 12 to 112
D
DH,DH3
>112 to 3
DH
DH3
Galvanized 12 to 3
DH
DH3
1. The availability of A563 grade DH nuts in nominal sizes 3/4″ and larger is very limited and generally available only on special orders of 50,000 or more. For smaller quantities, ASTM A194 grade 2H should be considered.