If you want a perfect, fantastic circuit board that is cut really well, I suggest you use something called Autoleveller. AutoLeveller - The height adjusting CNC software

Using a simple probe system like a croc clip attached to your machine, you can use your tool to probe the height of your PCB before cutting to get an accurate cut depth.

Simply get your g-code file from whatever your CAM output software is, import it into Autoleveller and it will automatically, based on your variables, edit the g-code to include a probe system before routing the board.

It is very clever and completely free.
Personally, I donated a fiver to the software designer as it's one of the best pieces of software I have used for cutting circuits.