I played with PCB milling for years. I never got what I called consistent results. I even built a vacumm hold-down board to ensure the board was flat. I changed all my screws to near zero backlash, etc, etc, etc. I finally gave up. There were a number of us working on the problems with outlining copper paths, tools overheating, gummy copper and other things. I finally went to an outside processor, Sunstone, who makes the boards almost overnight and ships them drilled and plated for about the same cost as the carbide cutters I ruined over and over.
I finally found a solution, at least partially, by making a floating pen holder and using my mill as a plotter. I used black and red sharpie brand pens and dipped the boards in hot FCL and they came out great. If you go this route, you will need to drill after you plot since the gummy copper chips will spin on the drill bit and ruin the plot.
Jerry