Hex Cap Screws
All Hex cap screws meet the following standard.
Grade 2: SAE J429 GRADE2 HEX CAP SCREW. ASME B18.2.1 1996 IFI-7
Grade 5: SAE J429 GRADE5 HEX CAP SCREW. ASME B18.2.1 1996 IFI-7
Grade 8: SAE J429 GRADE8 HEX CAP SCREW. ASME B18.2.1 1996 IFI-7
A325: ASTM 325 TYPE 1 BOLTS, ASTM A563 DH NUT,ASTM F436 TYPE 1 HARDEND WASHER
Minimum Thread Length Formula
For bolts 6” and shorter – Twice the diameter plus 1/4″ (2D + 1/4″)
Longer than 6” – Twice the diameter plus 1/2′ (2D + 1/2”)
When bolts are too short for Thread Length Formula, thread will extend as close to head as practical.
NOTE: Formula for Thread Lengths are MINIMUM, actual thread lengths may be longer.
Thread Series
Thread series cover designations of diameter/pitch combinations that are measured by the number of threads per inch (TPI) applied to a single diameter.
Coarse Thread Series (UNC/UNRC) is the most common designation for general application bolts and nuts. Coarse thread is beneficial, because they are less likely to cross thread, more tolerant in adverse conditions and facilitate quick assembly.
Fine Thread Series (UNF/UNRF) is commonly used in precision applications. Because of the larger tensile stress areas, they have high tension strength. However, a longer engagement is required for fine thread applications than for coarse series threads to prevent stripping.
| Coarse Thread Series – UNC | Fine Thread Series – UNF | ||||||
| Nominal Size &Threads / Inch | Basic Pitch Dia. | Section at Minor Dia. | Tensile Stress Area | Nominal Size &Threads / Inch | Basic Pitch Dia. | Section at Minor Dia. | Tensile Stress Area |
| 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 | 0.405 | 0.109 | 0.1187 |
| 1/2 – 13 | 0.45 | 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 | 0.566 | 0.202 | 0.226 | 5/8 – 18 | 0.5889 | 0.24 | 0.256 |
| 3/4 – 10 | 0.685 | 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 | 0.48 | 0.509 |
| 1- 8 | 0.9188 | 0.551 | 0.606 | 1-8 | 0.9459 | 0.625 | 0.663 |
| 1 1/8 – 7 | 1.0322 | 0.693 | 0.763 | 1 1/8 – 12 | 1.0709 | 0.812 | 0.856 |
| 1 1/4 – 7 | 1.1572 | 0.89 | 0.969 | 1 1/4 – 12 | 1.1959 | 1.024 | 1.073 |
| 1 1/8 – 6 | 1.2667 | 1.054 | 1.155 | 1 3/8 – 12 | 1.3209 | 1.26 | 1.315 |
| 1 1/2 – 6 | 1.3917 | 1.294 | 1.405 | 1 1/2 – 12 | 1.4459 | 1.521 | 1.581 |
| 1 3/4 – 5 | 1.6201 | 1.74 | 1.9 | — — | — | — | — |
| 2- 4 1/2 | 1.8557 | 2.3 | 2.5 | — — | — | — | — |
| 2 1/4 – 4 1/2 | 2.1057 | 3.02 | 3.25 | — — | — | — | — |
| 2 1/2 – 4 | 2.3376 | 3.72 | 4 | — — | — | — | — |
| 2 3/4- 4 | 2.5876 | 4.62 | 4.93 | — — | — | — | — |
| 3 – 8 | 2.8376 | 5.62 | 5.97 | — — | — | — | — |
| 3 1/4 – 4 | 3.0876 | 6.72 | 7.1 | — — | — | — | — |
| 3 1/2 – 4 | 3.3376 | 7.92 | 8.33 | — — | — | — | — |
| 3 3/4 – 4 | 3.5876 | 9.21 | 9.66 | — — | — | — | — |
| 4 – 4 | 3.8376 | 10.61 | 11.08 | — — | — | — | — |
Head Markings
Hex cap screws are available in different grades. Please see chart below for Imperial and Metric head markings.
Specifications
Material Specification and Tensile Strength
