Early on in planning the design for the Quadrotor, we knew that eventually some of the metal parts would need to be milled.  Having very little milling experience, other than a couple of basic-use classes at TechShop, I had no milling experience.  When it came time to start buying router bits for the ShopBot and Tormach CNC routers, I didn’t know what kind of bits were necessary.

Understanding End Mills

Greg over at 100kGarages put together a primer titled CNC Router Bits Demystified, which does a great job of explaining the basics of an End Mill, Ball Nose, Downcut, Upcut etc.