A milling machine is a machine tool that removes metal as the work is fed against a rotating multipoint cutter. The cutter rotates at a very high speed and because of the multiple cutting edges it removes metal at a very high rate. The machine can also hold more than one cutter at a time. This is why milling machines find wide application in production work. It is also superior to other machines in regard with accuracy and surface finish and is designed for machining a variety of tool room work.

Types of milling machines:

1) Column and Knee type

2) Fixed bed type

3) Planer type

4) Special type

Vertical Milling Machine:

A vertical milling machine can be distinguished from a horizontal milling machine by the position of its spindle which is vertical or perpendicular to the work table. The machine may be of plain or universal type and has all the movements of the table for proper setting and feeding of the work. The spindle head which is clamped to the vertical column may be swiveled at an angle, permitting the milling cutter mounted on the spindle to work on angular surfaces. In some machines the spindle can also be adjusted up or down relative to the work. The machine is adapted for machining grooves, slots and flat surfaces.

Principal Parts of a Milling machine:

• Base: The base of the machine is a grey iron casting accurately machined on its top and bottom surface and serves as a foundation member for all its other parts which rest upon it. It carries the column at one end. The base is kept hollow which serves as reservoir for cutting fluid.
• Column: The column is the main supporting frame mounted vertically on the base. The column is box shaped, heavily ribbed inside and houses all the driving mechanism for the spindle and table feed. The front vertical face of the column is accurately machined and is provided with dovetail guided ways for supporting the knee.
• Knee: The knee is a rigid grey iron casting that slides up and down on the vertical ways of the column face. The adjustment of height is affected by elevating screw mounted on the base that also supports the knee. The knee houses the feed mechanism of the table, and different controls to operate it. The top face of the knee forms a slide way for the saddle to provide cross travel of the table.
• Table: The table rest on the saddle and travels longitudinally. The top of the table is accurately finished and T-slots are provided for clamping the work and other fixtures on it. A lead screw under the table engages a nut on the saddle to move the table horizontally by hand or power.
• Overhanging Arm: The overhanging arm that is mounted on the top of the column extends beyond the column face and serves as a bearing support for the other end of the arbor. More than one bearing support may be provided for the arbor.
• Spindle: It is located in the upper part of the column n receives power from the motor through gears, belts and clutches and transmits it to the arbor. The front end of the spindle projects from the column face and is provided with a tapered hole into which various cutting tools and arbors may be inserted. The accuracy in milling depends on the spindle accuracy.
• Arbor: It may be considered as an extension of the machine spindle on which milling cutters are securely mounted and rotated. The arbors are made with taper shank for proper alignment with the machine spindles having taper holes at their nose. The arbor shanks are properly gripped against the spindle taper by a draw bolt.
• Front brace: It is an extra support that is fitted between the knee and the overarm to ensure further rigidity to the arbor and the knee.