Instead of always trying several wrenches to find the correct size I decided to make a little chart to stick to the front of the tool box.
HEX WRENCH SIZES
A = SAE number
B = hex wrench size for socket head cap screw
C = hex wrench size for set screw
Code:A B C
0 0.050 0.028
1 1/16 0.028
2 5/64 0.035
3 5/64 0.050
4 3/32 0.050
5 3/32 1/16
6 7/64 1/16
8 9/64 5/64
10 5/32 3/32