We sell sockets sets for the following nuts and bolts:
The tools for UNF and UNC are labeled AF. The abbreviation AF means Across Flat (American), this roughly means "measured crosswise" the sockets fit UNF and UNC threads. If the caliper indicates 9/16 "(14.2mm) when measuring the head, you should use a 9/16" socket. So the size of the head is decisive.
Whitworth (WW) Sockets
With the English Whitworth bolts and nuts, it is not the head but the diameter of the bolt that is decisive, so measure the diameter of the bolt first, if it is 3/8 "(9.5mm) you must use a socket that is suitable for 3 / 8 ".