TVET COLLEGE SUPPORT

MILLING MACHINE

 

Milling machine parts

 
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The different milling machines has common parts.  The main difference is in the pars is if it is a vertical or horizontal milling machine.

Vertical milling machine

Horizontal milling machine

Spindle motor
The spindle motor is connected to the all geared head or belt drive of the milling machine.  This motor will drive the spindle so that machining can be done.
 
Head
The head can be all geared for rapid spindle speed change, or belt driven with various pulleys sizes for different spindle speeds.  The all geared head is easy to use as changing gears is easy compared to moving belts to obtain different spindle speeds.
 
Ram or overarm
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.
 
Column and base
Column including base is the main casting that supports all other parts of milling machine.
  • 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.
Knee
It is a casting that supports the saddle and table. All gearing mechanism is enclosed within the knee.
  • It is fastened to the column by dovetail ways.
  • The knee is supported and adjusted by a vertical positioning screw (elevating screw).
  • The elevating screw is used to adjust the knee up and down by raising or lowering the lever either with the help of hand or power feed.
Saddle
The saddle is present on the knee and supports the table. It slides on a horizontal dovetail on the knee and dovetail is parallel to the axis of the spindle ( in horizontal milling m/c).
  • The swivel table (in universal machines only) is attached to the saddle that can be swivelled (revolved) horizontally in either direction.
Power Feed Mechanism
It is the knee which contains the power feed mechanism. It 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.
Table
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.
Spindle
It is the shaft that is used to hold and drives the cutting tools of the milling machine.
  • The 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 a tapered cutter holder or arbor. It has two keys at the front face which provides a positive drive for the cutter holder or arbor.
  • The drawbolt and jam nut is used to secure the holder and arbor in the spindle.
Arbor support
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 up to 25/100 mm.
  • 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.
Vertical positioning screw
The vertical positioning screw is used to position the table on the y axis.  The table is moved up and down using the vertical knee transverse crank.
 
Cross feed
The cross feed is used to position the table on the z axis.  The table is positioned on the z axis using the cross feed handle.
 
Overarm support
The overarm support assist when the overarm is adjusted far over.  It bolts on to the overarm an then onto the bed.  Is is deployed to reduce vibration especially during gang milling