Inch series · technical reference

Inch 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.

StandardASME B18.3 · Inch Series
RevisionSource review · 2026-08
Unitsinches
CAD ORTHOGRAPHIC REFERENCEASME B18.3.1A · INCH SERIES REFERENCE
CAD side orthographic view of an ASME B18.3.1A socket head cap screw
SIDE VIEW · LENGTH UNDER HEAD
CAD end orthographic view showing the hex socket of an ASME B18.3.1A socket head cap screw
END VIEW · HEX SOCKET

The drawing identifies dimension locations only. Use the table for nominal data and confirm the exact product configuration before ordering.

Reference head dimensions · inch series
Nominal threadUNC / UNF (TPI)Head diameter (A) max / minHead height (H) max / minHex key (J)Key engagement min (T)
#440 / 480.183 / 0.1760.112 / 0.1083/320.051
#632 / 400.226 / 0.2180.138 / 0.1347/640.064
#832 / 360.270 / 0.2620.164 / 0.1599/640.077
#1024 / 320.312 / 0.3030.190 / 0.1855/320.090
1/4 in20 / 280.375 / 0.3650.250 / 0.2443/160.120
5/16 in18 / 240.469 / 0.4570.312 / 0.3061/40.151
3/8 in16 / 240.562 / 0.5500.375 / 0.3685/160.182
1/2 in13 / 200.750 / 0.7350.500 / 0.4923/80.245
5/8 in11 / 180.938 / 0.9210.625 / 0.6161/20.307
3/4 in10 / 161.125 / 1.1070.750 / 0.7405/80.370