Print this design helper, then use it to see what size hole you need for your screws, screw heads, nuts or rods
hole are in 0.25mm increments i.e. the bottom hole is 2mm the next hole is 2.25mm

nut holes are scaled 1 : 1,   1 : 1.05,    1 : 1.10,    1 : 1.15

i.e. M3 nut is 1st. hole is 5.5mm  2nd. is 5.775 3rd is 6.05 4th. is 6.325