Inch series · technical reference
Socket Head Cap Screw Dimensions
Reference dimensions for inch-series hexagon socket head cap screws. The drawing uses an original CAD projection of a 1/4-20 UNC × 1 in reference instance; choose the exact UNC or UNF thread and L from the product listing.
Source: ASME B18.3 record in U.S. DoD ASSIST.
CAD ORTHOGRAPHIC REFERENCEASME B18.3.1A · 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) max / min | Head height (H) max / min | Hex key (J) | Key engagement min (T) |
|---|---|---|---|---|---|
| #0 | — / 80 | 0.096 / 0.091 | 0.060 / 0.057 | 0.050 | 0.025 |
| #2 | 56 / 64 | 0.140 / 0.134 | 0.086 / 0.083 | 5/64 | 0.038 |
| #3 | 48 / 56 | 0.161 / 0.154 | 0.099 / 0.095 | 5/64 | 0.044 |
| #4 | 40 / 48 | 0.183 / 0.176 | 0.112 / 0.108 | 3/32 | 0.051 |
| #6 | 32 / 40 | 0.226 / 0.218 | 0.138 / 0.134 | 7/64 | 0.064 |
| #8 | 32 / 36 | 0.270 / 0.262 | 0.164 / 0.159 | 9/64 | 0.077 |
| #10 | 24 / 32 | 0.312 / 0.303 | 0.190 / 0.185 | 5/32 | 0.090 |
| 1/4 in | 20 / 28 | 0.375 / 0.365 | 0.250 / 0.244 | 3/16 | 0.120 |
| 5/16 in | 18 / 24 | 0.469 / 0.457 | 0.312 / 0.306 | 1/4 | 0.151 |
| 3/8 in | 16 / 24 | 0.562 / 0.550 | 0.375 / 0.368 | 5/16 | 0.182 |
| 7/16 in | 14 / 20 | 0.656 / 0.642 | 0.438 / 0.430 | 3/8 | 0.213 |
| 1/2 in | 13 / 20 | 0.750 / 0.735 | 0.500 / 0.492 | 3/8 | 0.245 |
| 5/8 in | 11 / 18 | 0.938 / 0.921 | 0.625 / 0.616 | 1/2 | 0.307 |
| 3/4 in | 10 / 16 | 1.125 / 1.107 | 0.750 / 0.740 | 5/8 | 0.370 |
| 7/8 in | 9 / 14 | 1.312 / 1.293 | 0.875 / 0.864 | 3/4 | 0.432 |
| 1 in | 8 / 12 | 1.500 / 1.479 | 1.000 / 0.988 | 3/4 | 0.495 |
| 1-1/8 in | 7 / 12 | 1.688 / 1.665 | 1.125 / 1.111 | 7/8 | 0.557 |
| 1-1/4 in | 7 / 12 | 1.875 / 1.852 | 1.250 / 1.236 | 7/8 | 0.620 |
| 1-3/8 in | 6 / 12 | 2.062 / 2.038 | 1.375 / 1.360 | 1 | 0.682 |
| 1-1/2 in | 6 / 12 | 2.250 / 2.224 | 1.500 / 1.485 | 1 | 0.745 |