Technical Summary
dnominal diameter 
bminimum thread length 
dkhead diameter 
k max.maximum head height 
t min.minimum recess depth 
sdrive size 
StandardASME B18.3, ASTM F837-13e1(CW)

UNF Socket Head Cap Screws ASME B18. 3 . Also known as an Allen screw or Allen bolt, or simply a cap screw, socket head cap screws are a more modern alternative standard machine fastener to the standard hexagon headed bolt or setscrew, as found on much modern machinery.