Inch series · technical reference
Inch Button Head Cap Screw Dimensions
Reference dimensions for hexagon socket button head cap screws. This chart covers the ASME B18.3 inch-series form, not a generic pan-head or low-profile substitute.
Source: ASME B18.3 record in U.S. DoD ASSIST.
CAD ORTHOGRAPHIC REFERENCEASME B18.3.3A · INCH SERIES REFERENCE
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) max / min | Head height (H) max / min | Hex key (J) | Key engagement min (T) |
|---|---|---|---|---|---|
| #4 | 40 / 48 | 0.213 / 0.201 | 0.059 / 0.051 | 1/16 | 0.035 |
| #6 | 32 / 40 | 0.262 / 0.250 | 0.073 / 0.063 | 5/64 | 0.044 |
| #8 | 32 / 36 | 0.312 / 0.298 | 0.087 / 0.077 | 3/32 | 0.052 |
| #10 | 24 / 32 | 0.361 / 0.347 | 0.101 / 0.091 | 1/8 | 0.070 |
| 1/4 in | 20 / 28 | 0.437 / 0.419 | 0.132 / 0.122 | 5/32 | 0.087 |
| 5/16 in | 18 / 24 | 0.547 / 0.527 | 0.166 / 0.152 | 3/16 | 0.105 |
| 3/8 in | 16 / 24 | 0.656 / 0.636 | 0.199 / 0.185 | 7/32 | 0.122 |
| 1/2 in | 13 / 20 | 0.875 / 0.851 | 0.265 / 0.245 | 5/16 | 0.175 |
| 5/8 in | 11 / 18 | 1.000 / 0.970 | 0.331 / 0.311 | 3/8 | 0.210 |