PRINCIPAL PARTS OF COLUMN AND KNEE TYPE MILLING MACHINES

PRINCIPAL PARTS OF COLUMN AND KNEE TYPE MILLING MACHINES

Main parts of all the column and knee type milling machines are similar, the movements of the moving parts differ in then. All these machines essentially consists the following main parts:

1. BASE: 

It is heavy casting provided at the bottom of the machine. It is accurately machined on both the top and bottom surfaces. It actually acts as a load bearing member for all other parts of the machine. Column of the machine is secured to it carries the screw jack, which supports and moves the knee. It also serves as a reservoir for the coolant.

2. COLUMN: 

It a very prominent part of a milling machine and is produced with enough care. Various parts and controls are fitted to this. On the front face of the column are made the vertical parallel ways in which the knee slides up and down. At its rear side, it carries the enclosed motor drive. A cover is provided on this side, which can be opened to enable accessibility to the drive. Top of the column carries dove-tail horizontal ways for the over arm.

3. KNEE: 

It is a rigid casting, which is capable of sliding up and down along the vertical ways on the front face of the column. This enables the adjustment of the table height. The adjustment is provided by operating the elevating jack provided below the knee, by means of a hand wheel or application of power feed. 

Machined horizontal ways are provided on the top surface of the knee for the cross traverse of the saddle and hence the table. For efficient operation of the machine, rigidity of the knee and accuracy of its ways play an important role. 

On the front face of the knee two bolts are usually provided for securing the braces to it to ensure greater rigidity under heavy loads.

4. SADDLE: 

It is the intermediate part between the knee and the table and acts as a support for the table. It can be adjusted cross wise, along the ways provided on the top of the knee, to provide cross feed to the table. At its top, it carries horizontal ways along which table moves during longitudinal traverse.

5. TABLE: 

It acts as a support for the work. The work is mounted on it either directly or held in the dividing head. It is made of Cast Iron, with its top surface accurately machined and carries longitudinal T-slots to accommodate the clamping bolts for fixing the work.

Longitudinal feed is provided to it by means of a hand wheel fitted on one side of the feed screw. Cross feed is provided by moving the saddle and vertical feed by raising or lowering the knee. Both hand feed and power feed can be employed the adjustable stops should be used to trip out the same at the correct movement.

Modern milling machines provide rapid traverse in all the three directions to effect saving in time. In universal milling machines, the table can be swiveled in horizontal plane and the graduations on circular base help in adjusting required swivel.

6. OVER ARM: 

It is the heavy support provided on the top of both plain and universal milling machines it can slide horizontally, along the ways provided on the top of the column, and adjusted to a desired position in order to provide support to the projecting arbor, by accommodating its free end in yoke. If further support is needed, to have additional rigidity, braces can be employed to connect these when many cutters are used simultaneously.

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