Exchangeable ball-nose end mill heads have a rounded nose that mills complex shapes without sharp corners or creates round-bottomed slots and pockets. They have flutes that carry chips away from workpieces and a stem that connects to a compatible holder. These detachable heads can be replaced with new ones of the same type or different types without removing the holder from the machine. They require fewer tool changes than solid tools when making different types of cuts on the same workpiece.