The work table for drilling operations has motion laterally in two directions (one at a right angle to the other) by means of being carried on slides, and is fitted to a vertical slide on the face of the column so that it may be raised and lowered to suit the height of the work by means of the worm and worm-wheel shown, the latter being on the same shaft as a pinion engaging with a vertical rack on the face of the upright frame or column.
In [Fig. 1687] is represented a horizontal drilling and boring machine. In this machine the work-holding table is provided with a hand feed, and the drilling or boring spindle with hand and self-acting feed, the latter being variable to suit different kinds of work. The table has a compound motion upon suitable slideways and rests upon a frame or knee that is elevated by two vertical screws that are operated by hand wheel. This knee fits to a vertical slideway on the main frame, so that its upper face, and therefore the face also of the work table, is maintained parallel with the drill spindle at whatever height it may be set from it.
The arbor that carries the drill spindle is arranged with a face plate so that the machine can be used as a facing lathe. The feeds are arranged in two separate series, a fine and a coarse, and both of these series are applicable to any speed or any size of drill. The value of the coarse feed will be felt in all kinds of boring with bars and cutters, inasmuch as it is possible to rough out with a fine feed and finish with a light cut and a very coarse feed.
For work that is too large to be conveniently lifted to the table of a machine the floor boring machine is employed.
[Fig. 1688] represents a machine of this class, which consists of two heads that may be moved about upon, and secured to, any part of its base or bed plate to which the work is secured. The boring bar it will be seen stands horizontal, and may be set at any height from the base plate between the limits of 14 inches and 6 feet 4 inches, the driving head being raised on its slideway on the face of its standard or column by automatic mechanism. The feed is automatic and variable in amount to suit the nature of the duty.
The bar has eight speeds, four in single and four in double gear.
In order to insure that the crank pins of locomotive driving wheels shall stand with their axes parallel to that of the wheel shaft, and that they shall also stand 90° apart when measured on the wheel circle, it is necessary that the holes for these pins be bored after the wheels are upon their shaft, it being found that if the crank pin holes are bored before the wheels are upon the shaft they are liable to be out of parallel and out of quarter.
To avoid these errors a quartering machine is employed, such as shown in [Fig. 1689]. This machine consists of two heads carrying stationary or dead centres to hold the wheel axle, as in a lathe. Each of these heads is provided with a boring bar having an automatic and adjustable feed, the axes of these bars being 90°, or one quarter of a circle, apart.
As both crank pin holes are bored simultaneously and with the wheel rigidly fixed and held upon centres the work will obviously be true. This machine may also be used as an ordinary horizontal boring machine.