For a clearance hole you need a 9/64 drill bit.
quarter inch drill bit
That size is 8-32. The drill bit for a clearance hole is 11/64, or a #17 drill bit.
A 3/16 drill bit.
.50196850"
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.
If you want the bolt to slide through the hole a 5/16 hole will work well.
A 4 mm drill bit is equivalent to 5/32 inch.
accoring to the size.
.50 drill bit = 8mm rubber grommet
The drill bit size is always stamped on the shaft.