Vertical are so arranged that of the two motions (rotation and rectilinear translation) to he imparted to the tool the first is derived from a transmitting shaft driven by power, while the other is effected either automatically or by the hand or the foot of a workman. Figure 13 (pi. 24) shows a vertical drilling-machine for metals, in which the material to be drilled is secured to a table which can be adjusted at any height desired. The drill, fixed in a vertical spindle, receives its rectilinear motion by pressing down a treadle and its rotation by bevel-gear, from a revolving belt-driven shaft. The speed for every material has to be determined by experience, but to give different rates for drills of different diameters "stepped " or cone pulleys are provided. The drill-spindle, in order to acquire the motions to be imparted to it, passes through the hub of one of the bevel-gears, the latter being so con nected to the frame that it can be turned, but not shifted vertically.
A vertical automatic drilling-machine is shown in Figure 17 (.o/. 24). The drill-spindle is turned by a horizontal driving-shaft with cone pulleys, and a counter-shaft placed near the ceiling. By special gearing, consisting of two pairs of spur-wheels, the number of velocities can be increased to double the number of belts. Automatic advance of the drill is derived from the same driving-shaft by a belt-gearing (which can be run on three different pairs of pulleys, as seen on the right of the Figure), a horizon tal counter-shaft, a worm-wheel gear, a vertical auxiliary shaft, a pair of spur-wheels, and a nut and spindle. The latter being connected with the frame for sliding and with the drill-spindle for rotating, the rotation communicated to the nut is changed into vertical sliding of the drill spindle.
Some machines for drilling and boring give good examples of aggregate motions, the spindle carrying the cutting-tool turning rapidly and at the same time advancing slowly lengthwise. Suppose a screwed spindle to have upon it a spur-wheel and to bear a nut upon which there is a smaller spur-wheel; then, if these two spurs have different speeds, the spindle will not only turn, but will also advance lengthwise, and the rates of turning and advancing (or feeding) may be varied at will independently of each other. A self-acting drilling-machine which is not automatic turns the wheel attached to the nut by a power-driven bevel-wheel, while the wheel upon the spindle is worked through another one, upon a shaft having a wheel turned by hand at will. The drill-spindle has in its lower part a groove, and the inside of the tube, which bears the wheel giving the rotation, has in this groove a projection or feather, so that the spindle can move length wise, as though it were a part of the tube. In some machines a rack and
a pinion take the place of the screwed spindle. The self-acting part con sists of a small cone pulley, whose axis has a second endless screw and just over the end wheel a worm-wheel, which may be slid into gear, so that it can he turned by the driving-shaft. Bodmer's self-acting drill ing-machine has a screw-thread upon the drill-spindle, while a projection upon the inside of the boss of the lower wheel fits into a groove, so that the spindle can pass through the wheel, although they must turn together. A pipe-like nut having a wheel at the bottom receives the spindle. One pinion brings the drill down to the work, the other raises it, and the fine feed is the result of the combination of these two rates. In Whitworth's friction-drill the spindle has two worm-wheels, embracing its screwed portion upon opposite sides. If not permitted to turn, they form a nut which causes the spindle to move lengthwise; if free to move, the spindle will neither advance nor recede. The application of friction to retard them more or less makes the feed coarse or fine.
In the Elliott drill-press, shown in Figure 12 (pl. 25), the cone is hollow throughout and terminates in two sleeves, which constitute the journals upon which the cone revolves. Their bearings are of brass, made in two parts, and held in place after the manner of engine-lathes: the weight of the cone is taken upon a rawhide washer that rests upon the top of the lower brass bearing, which latter has a flange projecting upward around the washer, for the purpose of retaining the oil. The steel spindle, which carries the drill-chuck, passes through the sleeves, each of which forms for it a long bearing; the spindle is made to revolve with the cone by the driver, which is pinned to the spindle and whose ends embrace two rods, which form a part of the cone. Around the spindle and extending from the driver to the bottom of the cone is a steel spiral spring, which serves as a counterbalance to the spindle and chuck. Power to feed the drill is applied to a collar having a bearing directly over the chuck. The wear incidental to the thrust of feed-lever is taken by a rawhide washer. The lever, which is attached to the collar, is actuated by hand- or foot-levers through the medium of a rod inside the column; and when desired, the descent of the spindle may be accurately stopped at any given point by means of a clamp collar. The lower end of the hand-rod is connected with the inner arm of a segment, which is free between the forked ends of the hand-lever and foot-lever, either or both of which levers may be connected with the segment at any point by the insertion of pins. By loosening a set-screw the length of hand-lever may be changed to snit different workmen.