Fig. 1892.
[Fig. 1892] represents an attachment to this machine to facilitate cutting the teeth of gears, which it does because its index plate operates the work-holding mandrel direct, and may, therefore, be set quicker. The base bolts to the machine table and the index head and tailblock are traversed in the base by means of the four-levered handle shown.
Figs. from [1893] to [1899] represent a universal milling machine. This machine is so constructed that all the features essential to a universal milling machine are obtained by means of attachments (each complete in itself) which may be removed, leaving the work table clear, and, therefore, serviceable for large work, or work which may be more conveniently held without the use of attachments.
The T-slots in the table are furnished to standard size, and are at right angles, so that the attachments will be held exactly parallel with, or at a right angle, as the case may be, to the live spindle of the machine; hence the machine will accomplish all the varied results required in the tool room or for machine work generally.
Thus for the cutting of spirals, a fixture capable of originating any spiral right or left hand, from 2 inches to 6 feet pitch, is provided. Two bolts secure it to the machine table, and when the job is finished it is removed. Similarly for the cutting of cams, an attachment fastened to the work table by three bolts is used, which cuts either cylinder or face cams of considerable size, and as conveniently as a machine built solely for cam cutting. A gear-cutting device is also applied in the same manner, as well as plain or universal work-holding centres.
The essential features of the machine are a standard a, [Fig. 1894], with spreading base, carrying upon its top a driving cone b, which is fully back-geared like an engine lathe. The driving cone operates also the feed mechanism. Above the driving cone is an arch c, in which is inserted an arm d for supporting the outer end of the mill arbor when used for heavy work. Upon the face or front of the standard slides a knee e, which in its turn supports a carriage f, which traverses crosswise upon it and carries above it the work table, which is provided with an automatic feed at right angles with the movement of the carriage. These three movements, vertical, cross, and longitudinal, cover all that is usually required in a universal milling machine.
Coming to details we start with the spindle or arbor, the front end of which runs in bearings of bronze. These are made in two parts, tapering upon the outside and straight upon the inside, a corresponding taper hole to receive the spindle bearings being bored in the solid iron of the standard. A check nut upon each end of the bushing or bearing abuts against the end faces of the standard bearing, and by drawing the bushing or bearing through the taper hole in the standard, produces the exact required closeness of fit between the spindle journal and its bearing bore, and thus compensates for the wear of either the spindle journal or its bearing or bushing bore, the front check nut also providing a dust cap.
The back journal of the spindle runs in a bushing of considerable length. Upon the back end of the spindle is secured a train of feed gears g, the lower of which is upon a shaft that on its other end carries the first feed cone h. The corresponding feed cone i is fixed to the longer shaft j, carrying a worm (or tangent screw) k, which engages with the worm-gear l connected directly with the feed screw, for the longitudinal motion of the work table.