Modern Machine-Shop Practice Part 117

Fig. 1677 represents a drilling machine by Prentice Brothers, of Worcester, Ma.s.sachusetts. 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.

[Ill.u.s.tration: _VOL. I._ =LIGHT DRILLING MACHINES.= _PLATE XIX._

Fig. 1671.

Fig. 1672.

Fig. 1673.

Fig. 1674.

Fig. 1675.]

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:--

[Ill.u.s.tration: Fig. 1677.]

The worm shaft R is hollow, and through it pa.s.ses 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.

[Ill.u.s.tration: Fig. 1678.]

In the Sellers drilling machine, Fig. 1678, the drill spindle when in single gear is driven by belt direct, producing a uniform and smooth motion that is found of great advantage in drilling the smaller sizes of holes. The back gear is arranged to drive the spindle direct without the power requiring to be transmitted through a shaft, which induces vibration. The drill spindle is provided with variable rates of self-acting feed, but may also be moved rapidly by hand, and is counterbalanced. The work table is capable of revolving upon its axis, and the arm on which it is carried is pivoted in a slide upon a vertical slideway on the front of the main frame, so that the table and the arm may be swung out of the way for work that can be more advantageously rested on the base plate of the machine. A central hole is bored in the table, being true to the drill spindle when the arm is in its mid position, and clamps are provided to secure the circular table against rotation when it is set to place, and also to secure the swinging bracket to any required position. This form of table, like the compound table, has the advantage of permitting all parts of the table being brought in turn under the drill, but the motion is not in right lines.

Holes are provided in the circular table to admit holding-down bolts.

The rates of feed are proportioned to the kind of drilling to be done.

When the back gear is not in use and small drills are to be driven, the range of feeds is through a finer series than when the back gear is being used, and large drills or boring bars are to be driven.

Fig. 1679 represents a drilling machine of English design. The cone pulley A is provided with back gear B placed beneath it, the live spindle driving the drill spindle through the bevel gears C, one of which is fast upon a sleeve D through which the drill spindle E pa.s.ses.

The feed motions are obtained as follows:--I is the feed cone driving cone J, which drives a worm and worm-wheel at K. In one piece with the worm-wheel is a ratchet wheel L, and at M is a handle with a pawl that may be engaged with or disengaged from ratchet-wheel L. When it is engaged the handle, which is fast upon the vertical feed spindle N, is revolved by the worm-wheel and the automatic feed is put in operation; but when the pawl is disengaged the worm and worm-wheel revolve in the bearing while the spindle N remains at rest, unless it be operated by the handle M, which obviously revolves the spindle N more quickly than the worm and gives to a corresponding extent a quick motion to the drill spindle. Spindle N is provided with the gear-wheel O, which drives gear P, which is threaded upon the feed screw F and has journal bearing at Q.

The sleeve D has journal bearing at G and at H. At R is a hand wheel upon a horizontal shaft at whose other end is a bevel gear engaging with a bevel gear on the vertical screw for the knee T which fits to the vertical slides V. The work table W is fitted to a horizontal slide upon the arm X, which is pivoted to the knee T at Y, the handle for operating the screw of the table being at Z.

[Ill.u.s.tration: Fig. 1680.]

RADIAL DRILLING MACHINE.--Fig. 1680 represents a radial drilling machine, the column of which envelops a sleeve round which it may be swung or revolved, the sleeve extending some distance up from the base plate. The arm fits to the column and may be raised or lowered to any desired height to suit the work, the construction being as follows:--

[Ill.u.s.tration: _VOL. I._ =HEAVY DRILLING MACHINE.= _PLATE XX._

Fig. 1679.]

[Ill.u.s.tration: Fig. 1681.--Front View.]

[Ill.u.s.tration: Fig. 1682.]

[Ill.u.s.tration: Fig. 1683.--Side Elevation.]

[Ill.u.s.tration: Fig. 1684.--Front Elevation.]

Motion by belt is given to the spindle shown extending above the top of the column, and the pair of gears beneath it convey motion to the pair of bevels which drive the upper cone pulley which connects by belt to the lower one, which is provided with back gears to give the necessary changes of speed and power for the wide range of work the machine is intended for; the live spindle of the lower cone pulley extends past the collar and runs beneath the horizontal arm, giving motion to the drill spindle, which is carried in a sliding head. The spindle may be set at any required angle to the arm.

The vertical screw on the right hand of the column pa.s.ses through a nut in the column, so that by throwing the gearing at the upper end of the screw into action, the arm may be raised or lowered by power.

The vertical rod appearing in the front of the column and having an arm at its top, is for putting this gearing in or out of action, the arm being raised or lowered according to the direction in which the rod is operated by the lever handle shown upon it, and in front of the column.

The gearing at the top of the raising and lowering screw is constructed on the principle that was shown in Fig. 566, for reversing the direction of a lathe feed.

The capacity to swing the drill spindle at an angle enables the drilling of long work such as the f.l.a.n.g.es of pipes, by setting the pipe at an angle and swinging the spindle so as to stand parallel to it, while the facility with which the arm may be moved to any required position makes it easier to move the arm to the work, so that the latter will require but one chucking or setting.

Radial drilling machines are of various constructions. In some the drilling head is carried by an arm standing at a right angle to the main column or frame, and is capable of being moved to any required position upon the length of this arm. The arm itself is sometimes made capable of swinging upon its own axis, as shown in Fig. 1682.

It is also capable of being adjusted at any height from the bed or base plate upon which the upright or main frame sits, or above the work table when one is used as in the figure.

The advantage given by these facilities is that a heavy piece of work may be set upon the base plate or work table, and be drilled in various places without requiring to be moved.

Figs. 1681 and 1682 represent a radial drilling machine, in which the radial arm is carried on a head, which fits a vertical slideway provided on the face of the upright column, and may be moved to any required height on this slideway by means of a rack and worm gear, the latter being shown in the front view.

The seat of the arm on this head is cylindrical, the head being pivoted upon it in order that it may permit of its being rotated to hold the drill at an angle. The drill spindle is carried in a head sliding on the radial arm as already stated, and is driven as follows:--

Motion from the shop driving shaft is communicated by belt to the cone pulley shown at the base of the upright column.

The spindle of this cone pulley drives a belt which pa.s.ses up the column over an idle pulley on the sliding head that carries the radial arm; hence it pa.s.ses along the front of the radial arm and partly round a pulley on the drill spindle, two idle pulleys holding it in contact with the drill spindle pulley. Hence it pa.s.ses over a small pulley at the outer end of the radial arm, and returns along that arm through the sliding head, over an idle pulley to the pulley seen at the head of the vertical column, and from this pulley it pa.s.ses to the pulley that is on the cone spindle shaft at the base of the column. The drill is provided with an automatic feed actuated by the worm shown on the drill spindle.

In Figs. 1683, 1684, and 1685 is represented a combined drilling and boring machine.

It is provided with an horizontal as well as with a vertical spindle, either of which may be used for boring as well as for drilling. In the case of the vertical spindle the boring bar may extend down and have journal bearing in a block, or bearing secured to the base plate I.

Each spindle has eight changes of speed, four in single, and four in double gear, that is when the back gears at _a_ are in operation.

Motion from the pulley K on the cone spindle is conveyed by belt B to pulley L, whose hub extends through the frame at R and affords journal bearing to that end of spindle S which has a feed motion at H. Motion is conveyed from the cone spindle to vertical spindle _m_ as follows:--

[Ill.u.s.tration: Fig. 1685.]

Referring to Fig. 1685, bevel-wheel _f_ is on the end of the cone spindle and drives bevel-wheel _g_, which drives spindle _m_. This spindle is provided with an automatic as well as a hand-feed motion, the construction being as follows:--

Referring first to the automatic feed, the cone pulley E', Fig. 1685, which is upon the main cone spindle of the machine, drives cone E, Fig.