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. | |||
| 3⁄8 - 16 | 0.3344 | 0.0678 | 0.0775 | 3⁄8 - 24 | 0.3479 | 0.0809 | 0.0878 | -- -- | -- | -- | -- |
| 7⁄16 - 14 | 0.3911 | 0.0933 | 0.1063 | 7⁄16 - 20 | 0.4050 | 0.1090 | 0.1187 | -- -- | -- | -- | -- |
| 1⁄2 - 13 | 0.4500 | 0.1257 | 0.1419 | 1⁄2 - 20 | 0.4675 | 0.1486 | 0.1599 | -- -- | -- | -- | -- |
| 9⁄16 - 12 | 0.5084 | 0.162 | 0.182 | 9⁄16 - 18 | 0.5264 | 0.189 | 0.203 | -- -- | -- | -- | -- |
| 5⁄8 - 11 | 0.5660 | 0.202 | 0.226 | 5⁄8 - 18 | 0.5889 | 0.240 | 0.256 | -- -- | -- | -- | -- |
| 3⁄4 - 10 | 0.6850 | 0.302 | 0.334 | 3⁄4 - 16 | 0.7094 | 0.351 | 0.373 | -- -- | -- | -- | -- |
| 7⁄8 - 9 | 0.8028 | 0.419 | 0.462 | 7⁄8 - 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 |
| 11⁄8 - 7 | 1.0322 | 0.693 | 0.763 | 11⁄8 - 12 | 1.0709 | 0.812 | 0.856 | 11⁄8 - 8 | 1.0438 | 0.728 | 0.790 |
| 11⁄4 - 7 | 1.1572 | 0.890 | 0.969 | 11⁄4 - 12 | 1.1959 | 1.024 | 1.073 | 11⁄4 - 8 | 1.1688 | 0.929 | 1.000 |
| 13⁄8 - 6 | 1.2667 | 1.054 | 1.155 | 13⁄8 - 12 | 1.3209 | 1.260 | 1.315 | 13⁄8 - 8 | 1.2938 | 1.155 | 1.233 |
| 11⁄2 - 6 | 1.3917 | 1.294 | 1.405 | 11⁄2 - 12 | 1.4459 | 1.521 | 1.581 | 11⁄2 - 8 | 1.4188 | 1.405 | 1.492 |
| -- -- | -- | -- | -- | -- -- | -- | -- | -- | 15⁄8 - 8 | 1.5438 | 1.68 | 1.78 |
| 13⁄4 - 5 | 1.6201 | 1.74 | 1.90 | -- -- | -- | -- | -- | 13⁄4 - 8 | 1.6688 | 1.98 | 2.08 |
| -- -- | -- | -- | -- | -- -- | -- | -- | -- | 17⁄8 - 8 | 1.7938 | 2.30 | 2.41 |
| 2 - 41⁄2 | 1.8557 | 2.30 | 2.50 | -- -- | -- | -- | -- | 2 - 8 | 1.9188 | 2.65 | 2.77 |
| 21⁄4 - 41⁄2 | 2.1057 | 3.02 | 3.25 | -- -- | -- | -- | -- | 21⁄4 - 8 | 2.1688 | 3.42 | 3.56 |
| 21⁄2 - 4 | 2.3376 | 3.72 | 4.00 | -- -- | -- | -- | -- | 21⁄2 - 8 | 2.4188 | 4.29 | 4.44 |
| 23⁄4 - 4 | 2.5876 | 4.62 | 4.93 | -- -- | -- | -- | -- | 23⁄4 - 8 | 2.6688 | 5.26 | 5.43 |
| 3 - 4 | 2.8376 | 5.62 | 5.97 | -- -- | -- | -- | -- | 3 - 8 | 2.9188 | 6.32 | 6.51 |
| 31⁄4 - 4 | 3.0876 | 6.72 | 7.10 | -- -- | -- | -- | -- | 31⁄4 - 8 | 3.1688 | 7.49 | 7.69 |
| 31⁄2 - 4 | 3.3376 | 7.92 | 8.33 | -- -- | -- | -- | -- | 31⁄2 - 8 | 3.4188 | 8.75 | 8.96 |
| 33⁄4 - 4 | 3.5876 | 9.21 | 9.66 | -- -- | -- | -- | -- | 33⁄4 - 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 | 1⁄4 to 11⁄2 |
A |
B,D,DH |
A,B,C,D,DH,DH3 |
||
| >11⁄2 to 2 |
A |
A |
C,D,DH,DH3 |
|||
| >2 to 4 |
A |
C,D,DH,DH3 |
||||
| Any | 1⁄4 to 11⁄2 |
A |
B,D,DH |
A,B,C,D,DH,DH3 |
||
| >11⁄2 to 2 |
A |
A |
||||
| >2 to 4 |
A |
|||||
| Plain | 1⁄4 to 11⁄2 |
C |
D,DH |
C3,D,DH,DH3 |
||
| >11⁄2 to 4 |
C |
C3,D,DH,DH3 |
||||
| Galvanized | 1⁄4 to 11⁄2 |
DH |
||||
| >11⁄2 to 4 |
DH |
|||||
| Plain | 1⁄4 to 11⁄2 |
DH |
DH |
D,DH,DH3 |
||
| >11⁄2 to 4 |
DH |
DH3 |
||||
| Plain | 1⁄4 to 11⁄2 |
B |
D,DH |
B,C,C3,D,DH,DH3 |
||
| >11⁄2 to 3 |
A |
C,C3,D,DH,DH3 |
||||
| Galvanized | 1⁄4 to 11⁄2 |
DH |
D,DH |
D |
||
| >11⁄2 to 3 |
DH |
D |
||||
|
A687 |
Plain | 5⁄8 - 3 |
D |
DH,DH3 |
||
| Galvanized | 5⁄8 - 3 |
DH |
||||
| Any | 1⁄2 to 11⁄2 |
A |
B,D,DH |
A,B,C,D,DH,DH3 |
||
| >11⁄2 to 4 |
A |
C,D,DH,DH3 |
||||
| Plain | 1⁄2 to 11⁄2 |
A |
B,D,DH |
A,B,C,D,DH,DH3 |
||
| >11⁄2 to 4 |
A |
C,D,DH,DH3 |
||||
| Galvanized | 1⁄2 to 4 |
A |
C,D,DH,DH3 |
|||
| Plain | 1⁄2 to 11⁄2 |
D |
DH,DH3 |
|||
| >11⁄2 to 3 |
DH |
DH3 |
||||
| Galvanized | 1⁄2 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. | ||||||