Skateboard bearing sizes:
22 mm outer diameter (make holes 22.2 mm so bearings will fit)
8 mm inner diameter (make a round axle 7.8 mm to ensure it will fit)
7 mm width
Screw Sizes:
0.190 inch diameter
Make holes 0.210 inch to allow the screw to fit in the hole
Make holes 0.185 inch to allow the screw to thread into a hole