Inch series · technical reference
Flat Head Socket Cap Screw Dimensions
Reference dimensions for the 82° hexagon socket flat countersunk head cap screw form. This is an inch-series ASME B18.3 chart, not the 90° metric ISO 10642 form.
Source: ASME B18.3 record in U.S. DoD ASSIST.
CAD ORTHOGRAPHIC REFERENCEASME B18.3.2 · INCH SERIES REFERENCE
Reference size shown: 1/4-20 UNC. The drawing identifies dimension locations only. Use the table for nominal data and confirm the exact product configuration before ordering.
| Nominal thread | UNC / UNF (TPI) | Head diameter (A) sharp max / abs min | Head height ref (H) | Hex key (J) | Key engagement min (T) |
|---|---|---|---|---|---|
| #4 | 40 / 48 | 0.255 / 0.218 | 0.083 | 1/16 | 0.055 |
| #5 | 40 / 44 | 0.281 / 0.240 | 0.090 | 5/64 | 0.061 |
| #6 | 32 / 40 | 0.307 / 0.263 | 0.097 | 5/64 | 0.066 |
| #8 | 32 / 36 | 0.359 / 0.311 | 0.112 | 3/32 | 0.076 |
| #10 | 24 / 32 | 0.411 / 0.359 | 0.127 | 1/8 | 0.087 |
| 1/4 in | 20 / 28 | 0.531 / 0.480 | 0.161 | 5/32 | 0.111 |
| 5/16 in | 18 / 24 | 0.656 / 0.600 | 0.198 | 3/16 | 0.135 |
| 3/8 in | 16 / 24 | 0.781 / 0.720 | 0.234 | 7/32 | 0.159 |
| 1/2 in | 13 / 20 | 0.938 / 0.872 | 0.251 | 5/16 | 0.172 |
| 5/8 in | 11 / 18 | 1.188 / 1.112 | 0.324 | 3/8 | 0.220 |
| 3/4 in | 10 / 16 | 1.438 / 1.355 | 0.396 | 1/2 | 0.220 |
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