The simplest class of drilling-machines are fiddling drills, which are represented by Fig. 272, and are rotated by the drill-bow shown by Fig. 274. The next class of what may be termed drilling-machines are crank-braces, shown by Figs. 276 and 360. Another class of small tools for drilling are swing-braces, denoted by Fig. 363, which should be termed ratchet-levers. (See page 122.) All such machines make holes by causing their drills to rotate while the pieces in contact being drilled are relatively stationary. The drilling-machines to be here mentioned, are also those which make holes by rotating their drills; but are specially termed drilling-machines. These are capable of making holes small and large, to about two or three feet in length and ten or twelve inches in diameter. All of them form cylindrical holes whose lengths are vertical; or, strictly speaking, form cylindrical holes whose planes are horizontal. While such are in action with the drills connected, the lengths of the drills are vertical, for which reason they are named vertical drilling-machines, or briefly, verticals.

The value of a vertical is estimated by its capability of making cylindrical holes. The forming of straight holes which are truly circular, is the great requisition in all such machines whether small or large, although they are occasionally used for a few other purposes, the details of which are given in the ensuing processes.

To produce a cylindrical hole whose planes are horizontal, either one of these three plans may be adopted: a drill-point or other tool-point may be made to generate a helical or screw motion whose axis is vertical, while the piece in contact being drilled is stationary; or the piece may be made to generate a circular motion while the drill-point is slowly advanced in a right line; or both the drill-point and the object being drilled, may be made to generate helical motions at the same time, in which case the direction of the object's motion while being cut, is opposite to that of the cutting tool or drill. Of these three modes, the first mentioned is that which is adopted for verticals ; the second plan being that which is used in lathes ; the third plan, consisting in making both the object and the tool rotate at the same time, is seldom resorted to. We have to here consider only the movements belonging to verticals.

The drilling-machine shown by Fig. 836, mainly consists of an F-shaped standard similar to that of a slotter, and to the standard the apparatus for rotating the drill is connected. The table may be termed the next principal part of the machine, being that on which the object to be drilled is bolted, and seen at the front of the Figure. The spindie whose length is in a vertical position is the drill-spindle, in the lower end of which the drill is fixed and thereby rotated. This rotary movement is obtained by means of the bevel wheel seen on the spindle, the teeth of which are engaged with those of another bevel wheel whose spindle is rotated with the step-pully and machine-band.

In addition to the rotary movement of the drill-spindle, it has also a downward vertical motion while cutting, which is obtained by rotating the hand-wheel named the feed-wheel, denoted by F W, to which the feed-spindle is keyed. At the upper end of the spindle is keyed a worm-pinion, and by this being rotated the worm-wheel in contact is also rotated, actuating a pinion situated at the further side of the machine. The use of this pinion is to raise and lower the row of teeth shown by R, termed a rack ; and through the rack being attached to the drill-spindle, the up-and-down movement is obtained when desired by rotating the feed-wheel. The short band denoted by F B, is the feed-band, and is used when a long hole is being made to avoid the necessity of working the hand-wheel by the operator. At the time the feed-band is employed, a small worm-pinion is made to rotate the lower worm-teeth wheel, which is indicated by L W.

By reason of the bevel wheel situated on the drill-spindle being required to rotate the spindle while it advances either downwards or upwards, some means must be provided to admit this sliding motion, and the result is attained either by forming a key-groove along the length of the spindle and placing a key or ledge in the wheel's hole to fit the spindle groove, or by forming a ledge along the spindle to fit a groove in the wheel. Either of these arrangements will allow the spindle to be freely moved upwards and downwards without in any way altering the situation of the bevel wheel which transmits the rotary motion, and which must necessarily be at all times engaged with the bevel wheel situated on the pulley-spindle.

Fig. 837 represents a vertical whose action is similar to that of the one just described, but possesses additional apparatus termed power-gear. This consists of cog-wheels which are connected both to the pulley-spindle, and to the shaft immediately above, shown by A S. Both the wheels on this shaft are keyed tight in their required places, and remain so at all times. Such gear is required to obtain a comparative slow motion and great power for rotating the drill-spindle to make large holes. Such power not being required when making small holes, the wheels constituting the gear are disconnected at that time, and the disconnexion consists in sliding the shaft A S in the direction of its length in order to move the wheels keyed thereon away from the cog-wheels on the pulley-spindle. In order to cause the small wheel on the pulley-spindle to rotate independently of its spindle, when a slow motion is required, this wheel is allowed to be loose, but is permanently fixed or cast solid with the step-pulley, and therefore always moves with it. The large wheel on this same spindle is, however, keyed tight to it, instead of the pulley, and moves always in conjunction with the spindle either quick or slow, consequently when it is desired to quickly rotate the spindle for making small holes, the pulley is made to rotate its spindle by means of the fixing screw F, which slides along its slot in the wheel, and is made to grip a projection inside the pulley which is adjoining. To cause the pulley to rotate loosely, independently of the spindle, which is requisite when all the power wheels are connected with each other, the fixing screw is slid along the slot away from the projection or stop inside the pulley, and is firmly tightened at the inner end of the slot to prevent possibility of becoming loose while at work, and doing mischief.

The table of this machine (Fig. 837), to which the objects to be drilled are bolted, is similar to that shown in Fig. 836, and is a portable affair which may be detached when necessary.

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While the table is in use it is situated at the required height, and can be raised or lowered by means of the rack seen in the Figure. When the table is not required, as in cases of a long boring-rod being used, the machine appears as in the Figure (837). The rod is seen extending downwards to a base-plate or table, which is fixed so that its top is level with the floor. In the table are formed a number of slots for containing holdfast bolts, with which articles are fastened that require boring. Right-angular gauge-lines also are shown for adjusting the pieces previous to a final fastening. About the middle of the table a circular hole is carefully bored, its axis being exactly in line with the drill-spindle; and in the hole a garnisher with a hole of any desired diameter is denoted by G.

A machine which is both a slotter and driller is represented by Fig. 835. This is suited for small objects that require accurate and easy grooving, especially if the grooves to be formed are of comparative great length and situated in holes of small diameter. To avoid the tedium of chipping through a small hole of this character, the article can be fastened between the vee-clamp chuck in front of the machine, and grooved in a comparatively easy manner. The machine is worked by hand, the long handle-lever being moved up and down while the slotting-tool is in contact with the metal.

If holes are to be drilled with this machine, the long lever is disconnected, and the spindle is rotated by working the handle seen connected to the two bevel wheels, which resemble analogous wheels in all other drilling-machines, with the difference of working them by hand-power instead of by steam-power. The vee-clamp chuck of this machine will be found remarkably efficient for a rapid and accurate fixing of all small articles. It should be made with the upper surfaces of the two vee-clamps parallel with the table beneath, and also at the same height above it, which arrangement will allow an object to be quickly fixed with its lower surface at right angles to the vertical motion of the drill or slotting-tool, as required.