Hi, I use a 10° x 0.1mm V-Bit. You have to make sure to get the right board for the tools you have or else it will dull out the bits. For example I was using FR-4 board which ended up dulling the bits. So I used FR-1 boards with these tools and I got very thin, clean circuits. I got the circuits to go as thin as 0.5-0.6mm width. This is the link to the bits I have: https://amzn.to/2McX8je
If you want to see the end result using these bits and a cheap CNC router, check out my YouTube video of the process of making a PCB from start to finish. I am almost done editing part 2 of the video where I apply UV solder mask to protect the board.
Here is the link to my video: https://bit.ly/2G9fo9l