Some Basic Info Milling Machine

Milling is the process of removing metal by feeding the work past a rotating multipoint cutter. In milling operation the rate of metal removal is rapid as the cutter rotates at a high speed and has many cutting edges. Thus the jobs are machined at a faster rate than with single point tools and the surface finish is also better due to malfunctioning edges.

Milling machine is one of the most important machine tools in a tool room as nearly all the operations can be performed on it with high accuracy. The indexing head makes the machine suitable for so many purposes as exact rotation of job is possible by its use. Milling machine augments the work of a lathe and can produce the plain and curved surfaces and also helical grooves etc. the milling machine may be so arranged that the several cutters are mounted on the arbour at the same time, thus increasing the metal removal rate and allowing several surfaces to be machined at the same time. The single set-up thus arranged also ensures accuracy. It is also possible to adopt the machine to two position works, so that one station is loaded while the other is being worked on, thus assuring continuous machining. Further with the variety of flat and formed surfaces. It is possible to have relation motion between work piece and cutter in any direction and thus mill surfaces having any orientation.

The action of a milling cutter is vastly different from that of a drill or lathe tool. In milling operation, the cutting edge of the cutter is kept continuously in contact with the material being cut. The cut picks up gradually only. The cycle of operation to remove the chip produced by each tooth is first a sliding action at the beginning, the cutter comes into contact with the metal and then crushing action takes place just after it leading finally to the cutting action. In some metals this peculiar action produces a hardening effect called ‘work- hardening’ which complicates the milling operation considerably, since it throws an increased strain on the teeth of the cutter.

Milling machines can be used for machining flat surfaces, contoured surfaces, complex and irregular areas, surfaces of revolution, slotting, external and internal threads, gear cutting, helical surfaces of various cross- sections etc. to close tolerances for both limited quantity and mass production.

The versatility and accuracy of the milling process causes it to be widely used in modern manufacturing.

Historical Background

The first milling machine came into existence in about 1770 and was of French origin. The milling cutter was first developed by Jacques De Vaucanson in the year 1782. The first successful plain milling machine was designed by Eli Whitney in the year 1818. Joseph R Brown a member of Brown and Sharp Company invented the universal milling machine in the year 1861.

The ancestry of the milling machine may be traced to the lathe where premature milling operations were first performed by holding a small circular saw or cutter on an arbor between the lathe centres, while the work was held by clamps to the tool holder block of the lathe carriage. The simple process has been developed by a gradual improvement in the design of milling machines.

Working Principle

The working principle employed in the metal removing operations on a milling machine operation is that the work is rigidly clamped on the table of machine and revolving multi-teeth cutter mounted either on a spindle or a arbor.  The cutter revolves at a fairly high speed and the work fed slowly, past the cutter. The work can be fed in a longitudinal or cross direction. As the work advances, the cutter removes the metal from the work surface to produce the desired shape.