Double-end ball end mills have a rounded nose on both their ends and create a round-bottomed groove in milling tasks. Also known as ball-nose end mills, ball end mills are rotated against a workpiece to make round-bottomed slots and pockets or mill complex shapes without sharp corners. These end mills have cutting edges on both ends and can accomplish more milling tasks than single-end end mills before they need to be replaced. When the cutting edges on one end wear down, the end mill can be flipped over to expose the fresh cutting edges on the other end. Double-end ball end mills are used on CNC or manual milling machines.