Fig. 1697.—PULLEY-BORING MACHINE.
[Fig. 1697] represents a special machine for boring pulleys, &c. The advantage possessed by this class of machine is fully set forth in the remarks upon Boring and Turning Mills, and with reference to [Fig. 725]. The tool bar is fed vertically to the rotating pulley, and has three changes of feed; viz. .0648, .0441, and .0279 of an inch per rotation of the work. Its weight is counterbalanced.
The speed of rotation of the work table or chuck plate may, by means of the four steps on the cone pulley, be varied as follows:—63, 43, 19, or 10 revolutions per minute, which speeds are suitable for work bores ranging from 1 to 71⁄2 inches in diameter, the power exerted at the tool-point being for the latter diameter 1800 lbs.
Fig. 1698.—COMBINED DRILLING AND COTTER-DRILLING MACHINE.
The tool bar feed is operated by the upper cone pulley, and the worm and worm-wheel shown, the small wheel giving the automatic feed by a suitable friction plate, and the large hand wheel operating the bar quickly to elevate it after it has carried its cut through. When the drill is given a traverse back and forth, it obviously cuts out a slot or keyway whose width is equal to the diameter of the drill, and whose length equals the amount of traverse given to the drill. Special forms of drill are used for this purpose, and their forms will be shown hereafter. The machines for using these drills are termed traverse or cotter drilling machines. In [Fig. 1698] is represented a combined drilling and cotter drilling machine. This machine consists essentially of a drilling machine provided with automatic feed motions for cotter drilling; these motions consisting of a self-acting traverse to the sliding head carrying the drill spindle, and a vertical feed, which occurs at the end of each traverse, and during a short period of rest given to the sliding head carriage, or saddle as it is promiscuously termed. The slideway for this head stands vertical and extends across the top of the frame.
The belt motion is conveyed up one end and then on the top of the slideway, driving the spindle direct by means of a pulley. The traverse of the head or saddle in cotter drilling is accomplished by means of a peculiar arrangement of screws and adjustable nuts, which can be instantly set to the required length of slot, and insures a uniform motion, back and forth, at each stroke, the length of the stroke being uniform, as is also the rate of its advance. The vertical position of the drill spindle is of great advantage in cotter drilling wrought iron or steel, as the slot in process of cutting can be kept full of oil.
The feed motions for cotter drilling may be instantly thrown out of gear when not required, remaining at rest and leaving the machine a simple traverse drill with automatic feeds.