Homebrew PCBs

Hello everybody in this list. I've a cnc machine purchased some time
ago, but never used. Now it's time to use it and produce first pcbs.

Can you help me to find an appropiate router bit to produce boards
with 12 mil width of nets and 12 mil spacing between coper nets. For
example, some microcontrollers from microchip comes in an tqfp 64 pins
in an 10x10 mm space. I need to find a bit suitable for this job, but
I'm very new to cnc world. Can you recommend what type of bit should I
use? Diameter, angle, material, best rotation speed, ...?

Any help with this will be appreciated, as I've never used my cnc before.