The feed motions are obtained as follows:—
On the drill spindle is a feed cone m which is connected by belt to cone n, which drives a pinion o, that engages a gear p upon the feed spindle q, which has at its lower end a bevel pinion, which drives a bevel gear upon the worm shaft r. The worm shown on r drives the worm-wheel s, whose spindle has a pinion in gear with the rack t, which is on a sleeve u on the drill spindle g. It is obvious that when the rack t is operated by its pinion the sleeve u is moved endways, carrying the feed spindle with it and therefore feeding the drill to its cut, and that as the feed cone m has three steps there are three different rates of automatic feed.
To throw the self-feed into or out of action the following construction is employed:—
The worm-wheel s has on its hub face teeth after the manner of a clutch, and when these teeth are disengaged from the clutch sleeve w the worm-wheel s rides or revolves idly upon its shaft or spindle, which therefore remains at rest. Now the clutch sleeve s has a feather fitting to its spindle or shaft, so that the two must, if motion takes place, revolve together, hence when w is pushed in so as to engage with s, then s drives w and the latter drives the spindle, whose pinion operates the rack t.
A powerful hand feed to the drill spindle is provided as follows:—
The worm shaft r is hollow, and through it passes a rod having at one end the hand nut v and at the other a friction disk fitting to the bevel gear shown at the right-hand end of the worm-shaft. This friction disk is fast upon the worm-shaft and serves to lock the bevel gear to the worm-shaft when the nut v is screwed up, or to release it from that shaft when v is unscrewed.
Suppose, then, that v is unscrewed and shaft r will be unlocked from the bevel-wheel and may be operated by the hand wheel x, which is fast upon the worm-shaft, and therefore operates it and worm-wheel s, so that w being in gear with s the hand feed occurs when x is operated and v is released. But as the motion of s is, when operated by its worm, a very slow one, a second and quick hand feed or motion is given to the spindle g as follows, this being termed the quick return, as it is mainly useful in quickly removing the drill from a deep hole or bore.
The spindle carrying s and w projects through on the other side of the head j and has at its end the lever y, hence w being released from s, lever y may be operated, thus operating the pinion that moves rack t, one revolution of y giving one revolution to the pinion, both being on the same shaft or spindle.
The work is carried and adjusted in position beneath the drill as follows:—
The base of the column or frame is turned cylindrically true at a, and to it is fitted a knee b which carries a rack c. The knee b affords journal bearing to a spindle which has a pinion gearing with the rack c, and at the end of this spindle is a ratchet-wheel d operated by the lever shown. A catch may be engaged with or disengaged from ratchet d. When it is disengaged the lever may be operated, causing the pinion to operate on rack c and the knee b to raise or lower on a according to the direction in which the lever is operated. As the knee b carries the rack the knee may be swung entirely from beneath the drill spindle and the work be set upon the base plate e if necessary, or it may be set upon the work table f which has journal bearing in the knee b, so that it may be revolved to bring the work in position beneath the drill.