Exchangeable slotting and slitting cutter heads are wide and flat with multiple cutting edges that make slots and slits in a workpiece. Sometimes called disc milling heads or T-slot mills, they cut slits of varying depths or make other slim cuts in cut-off and shouldering operations. These detachable heads have a stem that connect to a compatible holder. They can be replaced with new heads 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.