The machine is provided with a hand and a foot feed by means of the compound lever w z, [Fig. 1674], actuating the feed rod j, which passes up within the column and connects to the lever k, the latter being suspended by a link h.
[Fig. 1675] represents Slate’s sensitive drilling machine, in which the lower bearing for the live spindle is carried in a head h that fits to a slide on the vertical face of the frame, so that it may be adjusted for height from the work table w to suit the height of the work. l is a lever operating a pinion engaging a rack on the sleeve s to feed the spindle. The table w swings out of the way and a conically recessed cup chuck c is carried in a bracket fitting into a guideway in the vertical bed g. The cone of the cup chuck is central to or axially in line with the live spindle, hence cylindrical work may have its end rested in the cone of the cup chuck, and thus be held axially true with the live spindle.
Fig. 1676.
[Fig. 1676] represents a drilling machine in which the spindle has four changes of feed, and is fed by a lever handle operating a pinion that engages a rack placed at the back of a sleeve forming the lower journal bearing for the spindle. This lever is provided with a ratchet so that it may be maintained in a handy position for operating. The work table is raised or lowered by a pinion operating in a rack fast upon the face of the column, a pawl and ratchet wheel holding it in position when its height has been set. A lever is used to operate the pinion, being inserted in a hub fast upon the same spindle that carries the pinion and the ratchet wheel.
Fig. 1677.
[Fig. 1677] represents a drilling machine by Prentice Brothers, of Worcester, Massachusetts. Motion for the cone pulley a is received by pulleys b and is conveyed by belt to cone pulley c, which is provided with back gear, as shown; the driving spindle d drives the bevel pinion e, which gears with the bevel-wheel f, which drives the drill spindle g by means of a feather fitting in a keyway or spline that runs along that spindle. Journal bearing is provided to the upper end of the spindle at h and to the lower end by bearings in the head j, which may be adjusted to stand at, and be secured upon any part of the length of the slideway k. By this arrangement the spindle is guided as near as possible to the end l to which the drill is fixed and upon which the strain of the drilling primarily falls. This tends to steady the spindle and prevent the undue wear that occurs when the drill spindle feeds below or through the lower bearing.