12mm
That size is 8-32. The drill bit for a clearance hole is 11/64, or a #17 drill bit.
.50196850"
A 10 cm hole is almost 4 inches ! ! - IF you meant 10mm, then that's a little over 3/8 of an inch, or 13/32 for a clearance hole.
Surprisingly enough- a 6 mm drill bit, or if you don't have one,1/4 drill bit will do.
Drill bits are not universal. You choose the size of the drill bit according to the size of hole you like to make.
A 4 mm drill bit is equivalent to 5/32 inch.
accoring to the size.
.50 drill bit = 8mm rubber grommet
For a clearance hole you need a 9/64 drill bit.
The drill bit size is always stamped on the shaft.
An 'O' drill bit is a decimal size, 0.3160 inch, which is between 5/16 and 21/64 on the fractional inch scale.