Milling machines are categorized by their orientation to their workpiece and their degree of motion.
Knee-Type milling machines employ a vertical workspace supported by a knee, which is an adjustable vertical casting. The knee supports a saddle and can be adjusted to allow for a customizable workspace.
Milling machines with a standard work surface can either be oriented vertically or horizontally. The tooling assembly is generally affixed on a turret and swivel, typically positioned parallel to the workspace. The turret and swivel allow the tool to move freely around the workpiece to enforce tight tolerances.
A universal horizontal milling machine differs from the plain horizontal type because it has a table swivel housing, which allows the table to move out 45 degrees from the standard horizontal position. This workpiece movement allows for easier angular or helical milling operations.
Ram-Type and Universal Ram-Type Milling Machines
A ram-type machine is used to allow the tooling to position itself on a greater range of space with regards to the workpiece. The ram-type machine has a spindle on a movable housing, which can move within a set horizontal plane. The universal ram-type milling machine includes a swivel housing that increases the range of cutting movements.
Swivel Cutter Head Ram-Type Milling Machine
With a swivel cutter, a milling machine can rotate from a completely vertical to a completely horizontal position. The worktable also moves, providing the user with a very liberal degree of motion and orientation. Many swivel cutters include both automatic or hand driven settings, increasing operation options.