Page:Practical Treatise on Milling and Milling Machines.djvu/23

 Vertical Spindle Milling Machine. The vertical spindle milling machine embodies the principles of a drilling machine. The spindle and table are similarly located, and the cutter is mounted at the end of the spindle. The table on the milling machine, however, has a series of movements that are not found on the drilling machine. For such work as face milling, die-sinking, profiling, etc., the vertical spindle machine offers many advantages over the horizontal style. Some work can be fastened directly to the top of the table, eliminating the use of special fixtures necessary for the same kind of work on a horizontal spindle machine. Furthermore, the operator is enabled to see his work at all times during operation and more readily follow any irregularities in outline. This feature is especially valuable in profiling, cutting odd-shaped slots, etc.

Not all vertical spindle machines are of the column and knee type. There are several styles that have no provision for vertical adjustment of the table. Also some vertical spindle machines have two spindles instead of one, but these are more generally known as profiling machines.

But the combination of the vertical spindle and column and knee constructions has given the mechanical world an exceptionally valuable machine tool. With it, all of the advantages of the vertical spindle, together with those of the column and knee, are acquired. A modern example of this style is shown on the cut on the opposite page. A further convenience of this machine is found in the spindle head, which is adjustable vertically, and can be fed by power, thus enabling drilling to be conveniently done. With the adjustable spindle head and column and knee construction, it is apparent that work of a wide range of heights can be accommodated. Another syle of vertical spindle machine, where the spindle is driven by a belt, is shown on page 36.

Different methods of Driving Milling Machines

Milling machines of the column and knee and manufacturing types are either cone driven or gear driven. The latter class is more commonly referred to as the "constant speed drive."

Cone Drive. In cone driven milling machines, the belt runs directly from a stepped or cone pulley on the countershaft to one of like design fastened, either directly to, or mounted on a sleeve on the machine spindle. In one case the spindle is driven directly and only speeds that are obtained by shifting the driving belt on the pulley steps are available; while in the other an additional series of speeds is procured by the employment of back gears. The cut on page 10 is of the