Many cutters can be used with CNC machines and it is much like the preference for cars or women-- it depends!

At the risk of going nuts, I have more less settled on two types of cutter and each has their application. The first is engraving bits and the second is four flute end mills.

• The Engraving bits come in various angle widths as they cretae a "V" shaped cut in the stock. I find that the 60 Degree bit for cutting circuit traces works best for me as it gives sharp cuts that are narrow but deep enough to provide isolation from the surrounding media. Often I will use the CNC Mill to cut down a smaller board from a larger piece of stock. the engrvaing bits are not suited for this purpose as you have to create a very large "V Section" to separate the piece needed.
• The Four Flute End Mill is better used for the task of cutting boards. Typically I use a 1/32 inch end mill. Yes -- just look at them and they break. But the end mill is also useful for cutting slots in PC Boards such as cutouts for RF Transistors.

A good example where both cutters are used is a Driver and Final Amplifier Board use in one of my SSB transceivers.

 

 

The pads were cut using the 60 Degree Engraving Bit, but the hole cutout for the IRF510 was cut using the Four Flute 1/32 inch end mill.