The milling machine (Fig. 199) is not so generally used as its worth merits, because comparatively few machinists know how to operate it. This machine is not limited to plane milling, but will mill irregular shapes by the use of formed cutters. The work is done by fastening to the bed the casting or metal, held in a chuck or on centers. The variety of operations which the milling machine can perform is almost limitless. The work is fed against a cutter whose teeth are so cut that it works on the principle of a coarse file. Spur gears, bevel gears, and spiral gears may be cut, taps and reamers fluted, and many other things performed which could be done on other machines only with difficulty, unless the machine were specially built. To run the milling machine to its best advantage a knowledge of trigonometry is required. Charts are furnished covering the most common requirements, but to cover everything the machine can do would require an unreasonable number of charts.

There are three classes of milling machines: (1) the plane milling, (2) the universal milling, and (3) the special milling machine. The operation of successful milling requires much study of milling cutters. These cutting tools turn on the arbor (principal support) of the machine, while the table feeds the work horizontally, vertically, or crosswise. The action of the machine is as follows: The power is transmitted from the pulley on the countershaft to that on the spindle, causing the spindle which carries the cutter to revolve while the table to which the work is fastened travels by. The depth of cut can be regulated by the operator through the medium of screws which raise or lower the knee upon which the table is carried. The position of the cut is also controlled by a screw which operates the lateral motion.

Fig. 199   Universal Milling Machine.

Fig. 199 - Universal Milling Machine.