Column & Base
Column including base is the main casting that supports all other parts of milling machine. It is made of CI (cast iron).
- The column contains an oil reservoir and a pump which lubricates the spindle.
- The column rests on the base and base contains coolant reservoir and a pump which is used during machining operation that requires coolant.
It is a casting that supports the saddle and table. All gearing mechanism is enclosed within the knee.
- It is tied to the column.
- The knee is supported and adjusted by a vertical positioning screw also called elevating screw).
- The elevating screw is used to adjust the knee to raise it up and lower it down with the help of a lever. It uses the supports of hand and also can be operated with a power feed.
Power Feed Mechanism
The power feed mechanism is used to control the longitudinal ( left and right), transverse ( in and out) and vertical (up and down) feeds.
- To get the desired rate of feed on the machine, the feed selection lever is positioned as indicated on the feed selection plates.
- On some universal knee and column milling machine, the feed is obtained by turning the speed selection handle until the desired rate of feed is indicated on the feed dial.
- Most of the milling machines have a rapid traverse lever that can be engaged when a temporary increase in the speed of the longitudinal, transverse or vertical feeds is required. For example this lever would be engaged when the operator is positioning or aligning the work.
It is a rectangular casting which is present on the top of the saddle.
- It is used to hold the work or work holding devices.
- It contains several T-slots for holding the work and work holding devices (i.e. jigs and fixtures).
- The table can be operated by hand or by power.To move the table by hand, engage and turn the longitudinal hand crank. To move it through power, engage the longitudinal direction feed control lever.
It is the shaft which is used to hold and drives the cutting tools of the milling machine.
- Spindle is mounted on the bearings and supported by the column.
- Spindle is driven by the electric motor through gear trains. The gear trains are present within the column.
- The face of the spindle which lies near to the table has an internal taper machined on it. The internal taper at the front face of the spindle permits only tapered cutter holder or arbor. It has two keys at the front face which provides positive drive for the cutter holder or arbor.
- The drawbolt and jam nut is used to secure the holder and arbor in the spindle.
Over Arm / Overhanging Arm
It is a horizontal beam present at the top face of the column. It may be a single casting which slides on the dovetail ways present on the top face of the column.
- The overarm is used to fastened arbor support. It may consist of one or two cylindrical bars which slide through the holes in the column.
It is a casting with bearing that supports the outer end of the arbor. It also helps in aligning the outer end of the arbor with the spindle.
- It prevents the springing of outer end of the arbor during cutting operations.
- There are generally two types of arbor supports used in the milling machine. The first one has small diameter bearing hole, 1-inch in maximum diameter. And the other one has large diameter bearing hole, usually upto 23/4 inches.
- The arbor support has an oil reservoir that lubricates the bearing surfaces. It can be clamped anywhere on the overarm. The arbor support is used only in the horizontal types of milling machine.
The overhanging arm in the vertical machine is called ram. One end of the ram is mounted on the top of the column and on the other end milling head is attached.
- The ram can be a moved transversally ( in and out) on the column by a hand lever.