When To Use 2-flute, 3-flute And 4-flute End Mills | The ...
2 Flute end mills are used to plunge (drill) and cut slots. Since they have a larger gullet, they provide better chip clearance. If you are using a smaller mill, a 2 flute is a better roughing tool. For finish work or in hard materials, more cutting edges are desired, so a 3 or 4 flute end mill works better.