[Fig. 1907] represents a milling machine for globe valves and other similar work. Here there are two cutter-driving spindles, one on each end of the bed, and the work is held vertically. It is provided with an index wheel for milling squares, hexagons, or octagons, and the pen for the index wheel is operated by treadle. The work is fed across the bed, the chucking devices being carried on a slide rest. In the figure a globe valve is shown chucked between two plugs or arbors fitting its bore, but it is obvious that centres or other work-holding appliances may be used to suit the kind of work.
[Fig. 1908] represents an eighty-inch milling machine, the table of which has longitudinal motion; and provision for vertical and crosswise movements are made in the head which carries the driving mechanism.
The machine table sets low on a bed supported by four box legs, and is actuated by a steel screw driven by a worm and worm-gear connected with a pair of spur-gears. The gearing is outside the bed, and therefore accessible, and is protected by a shield, as shown in cut. The arrangement for belting to feed works is also shown too plainly to need description. The head upon which the spindle carrier is mounted travels in ways upon the bed, and is adjusted crosswise on it by means of a screw connected with a hand wheel, partially shown at the left of engraving. For convenience and ease in fine adjustment this wheel, and also the wheel at top of machine, connected with the elevating screw, are worked by a hand lever, the wheels having sockets in their periphery for this purpose.
The carrier, upon which is mounted the driving spindle, is gibbed to the head, and has a vertical range sufficient to allow work 18 inches high to pass under centres. From this carrier projects a large arm for outside centre support of mill spindle, intended for use on work where a back stand is not admissible. There is, however, as may be seen, a back stand or tailstock of a very solid character. The arm is readily removable, when desired, or the tailstock can be slid off its seat if required. In most cases, however, the arm need not be removed, the yoke on it being swung up out of the way, leaving the centre of mill arbor free to engage with that on the back stand. This combination provides for operating on a wide range of work.
As shown in the [engraving], the space between head and tailstock is about 24 inches, but if required the tailstock can be made to travel in line with the head, and its support be extended to any distance desired.
The method of driving the spindle is simple and strong, and allows of free adjustment of the spindle without disarrangement of the driving and feed belts.
The cone, which is made for 31⁄2 inch belt, is mounted in a stirrup which is pivoted to the bed, and the pinion which engages with the driving gear on the spindle is held at correct distance by a connecting yoke, and is driven by a feather.
The machine has longitudinal feed only, but where it is desired an automatic feed motion can be applied to the elevating screw in the head, giving feed in a vertical direction.
The table is arranged to be run back rapidly by power, by a device which is not seen in the engraving. As the table weighs one ton, the relief to the operator by this improvement is obvious.