MILLING MACHINE AND ITS PARTS

Milling machine may be defined as the type of machine in which the metal is removed by causing the job to be fed against a revolving cutting tool called the milling cutter, which has one or more cutting edges.

The principle parts of milling machine are given:

• Base

The base of the machine is Grey iron casting accurately machined on its top and bottom surface and serves as a foundation member for all the other parts which rest upon it. It carries the column at its one end. In some machines, the bage is hollowed and working as a reservoir for cutting fluid.

• Column

The column is the main supporting frame mounted vertically on the bage. The column is box shaped. Heavily ribbed inside and houses all the driving mechanisms for the spindle and table feed. The front vertical face of the column is accurately machined and is provided with dovetail guide ways of supporting knee. The top of the column is finished to hold an over-arm that extends outward at the front of the machine.

• Knee

The knee is the rigid gray iron casting that slides up and down on the vertical way of the column face. The adjustment of height is effected by elevating screw on the base that also supports the knee. The knee houses the feed mechanism of the table, and in different controls to operate it. The top face of the knee forms slid way for the saddle to provide cross travel of the table.

• Saddle

The saddle is placed on the top of the knee, which slides on guide ways set exactly at 90 to column face. A cross feed screw near the top of the knee engages a nut of the bottom of the saddle to move it horizontally, by hand or power, to apply cross feed. The top of the saddle is accurately machined to provide guide ways for the table.

• Table

The table rest on ways 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. The longitudinal travel of the table may be limited by fixing trip dogs on the side of the table. In universal machines, the table may also be swiveled horizontally. For this purpose the table is mounted on a circular bage which in its turn is mounted on the saddle. The circular bage is graduated in the degree.

• Over hanging arm

Over hanging arm is mounted on the top of column extends beyond the column face and serve as a bearing support may be provided nearest to the cutter. More than one bearing support may be provided for the arbor.

• Front Brace

The front brace is an extra support that is fitted between the knee and over arm to ensure further rigidity to the arbor and the knee. The front brace is slotted to allow for adjustment of the height of the knee relative to over arm.

• Spindle
  The spindle of the machine is locates in the upper part of the column and receive power from the motor through belts, gears and clutches and transmit it to the arbor the front end of the spindle just projects from the column face and it is provided with a tapered hole into to which various cutting tools and arbors may be inserted. The accuracy in metal machining by the cutter depends on primarily accuracy, strength and rigidity of the spindle.
• Arbor
  An arbor is considered as an extension of the machine spindle on which cutters are securely mounted and rotated. The arbors are made with taper shanks for proper alignments with machine spindles having taper hole on their nose. The taper shank of the arbor conforms to the Morse taper or self release taper whose value is 7:24. The arbor may be supported at the farthest end from the over hanging arm or may be of cantilever type which is called stub arbor.