For a 6mm hole, a 6mm standard drill bit should be used.
The size of the drill bit you should use for your project depends on the size of the hole you need to drill. Check the project specifications or use a drill bit sizing guide to determine the appropriate size for the job.
That depends on the size of the finish hole. It should be big enough so that the larger bit will grab in the hole and not skate off.
The recommended drill size for a hole that needs to be 6mm in diameter is 5.5mm.
A 6mm drill bit can drill a hole that is approximately 15/64 inches in size.
The standard size of a 6mm drill bit is 6 millimeters in diameter.
Drill bits are not universal. You choose the size of the drill bit according to the size of hole you like to make.
The recommended drill bit size for a 15/64 inch hole is a 15/64 inch drill bit.
I use a 3/16 drill bit for that.
For creating a pilot hole, use a drill bit that is slightly smaller in diameter than the screw you plan to use.
If you want it to grip, drill a 9/64 hole. For a clearance hole, drill 7/32.
The recommended size of the drill bit for a 7/16 inch hole is a 7/16 inch drill bit.
Most metals are initially drilled with a narrower drill, forming a pilot hole. Then the right size drill is used to complete the drilling of the hole by widening the pilot hole.