The only cutting in a drill bit is at the bottom because as they cut down the hole is already cut and you only need to evacuate the chips. Router bits from your router table will work in a cnc except for bits with bearings.

Regular router bits are used for carving and cutting in CNC routers, while some special router bits can be used in CNC milling machines to mill metal molds, CNC drilling machines to drill holes, and CNC machining centers to cut wood and metal with automatic tool changer, but the standard router bits cannot be used for ...

Re: How Many Flutes for Wood? You want adequate clearance for the chips -- which usually means two flutes. Frankly, your best bet is to use an actual router bit in your mill and run it as close to router/shaper speeds as you can. It will have the high positive rake and chip clearance you want.