This whole feed work is shown fully in outline in [Fig. 1894]. The arm m that supports the two lower feed gears pivots upon the outboard end of the back bushing, hence its centre coincides with that of the spindle. At its lower end a projection inwards forms a hub upon which a second lug or arm n is pivoted. The lower end of this arm is bored out to receive the threaded end of a lug o with the bearing of the second feed cone i. This threaded end carries a milled or hand nut p, so that to tighten or loosen the feed belt a turn of the nut is sufficient, the effect being to increase or diminish the distance between the feed cones h and i. The front end of the feed rod is supported in a drop box q, and is splined to allow the worm k to travel upon it. It will be seen, therefore, that the feed mechanism is undisturbed either by the vertical movement of the knee, or the cross motion of the carriage, or the longitudinal feed of the table. The feed gears are covered with a shield r, a part of which is shown broken away. The knee with its appendages is actuated vertically by means of a crank connected with bevel gearing at s, which moves a perpendicular screw t under the centre of the knee. Rotating with this crank-shaft is a finger u held by friction. This finger is in close proximity to a dial v graduated to thousandths of an inch, and as one revolution of the finger indicates 1⁄8 of an inch of elevation to the knee e, the ordinary subdivisions of an inch are obtained either with or without an inner circle of graduations on the dial. A similar dial upon the cross feed motion (not shown in the engraving) is also put on, which likewise reads to thousandths of an inch.
The feed of the work table is accomplished by means of a screw whose thread is in shape a half V and does not bear upon the bottom of the thread in the feed nut, which is in halves, with provision for closing up to compensate for wear, while check nuts on one end of the feed screw take up all end play.
The automatic feed is self-stopping (so as to enable one attendant to operate several machines) by means of the following construction:—
In the general view, [Fig. 1893], there is seen a stop that is secured in the required position in the T-groove shown at x in the outline view, [Fig. 1894], and when this stop meets the bell crank y it unlatches it from a lug which is on the drop box q, [Fig. 1893], hence this box falls and with it that end of the worm shaft j, throwing it out of gear with the worm-wheel l, and therefore stopping the feed.
The attachments giving to this machine its universal qualifications are as follows:—
The rotary vice is shown on the work table in the general view, [Fig. 1893]; and requires but little description. Upon the underside of the base is a circular projection having beneath it a projection fitting into the T-slots in the work table. Two segmental slots in the base admit of a rotary movement of the vice within a range of 90°, and it is held to the table by two bolts. The crank or handle of the vice is made more convenient by means of two square holes that fit the end of the screw that actuates the movable jaw. Using the central hole allows the handle to clear the work table, but when the vice jaws need to be closed with considerable force the handle is shifted to the end or outer hole, thus doubling the leverage.
Fig. 1895.
The Universal Head and Back Centre.—This tool is used for making milling cutters either straight or angular, cutting small gears either spur or bevel, fluting taps or reamers, finishing nuts or bolt-heads, and a multitude of other jobs too numerous to particularise. The head consists, as seen in [Fig. 1895], of a swinging block mounted centrally between the two upright sides or jaws of a base, and is clamped in any position by a set-screw on either side. The face of one side or jaw is laid out in degrees, and a finger or pointer on the block indicates its angle of elevation. On the front end of the spindle is secured a worm-wheel divided longitudinally, each half being used as a corrector (in the making) for the other half till all errors are eliminated. A dial is fixed upon the bushing through which passes the shaft that actuates the worm, and consequently revolves the worm-gear and the spindle. A pointer arm carrying a handle with a pointer and appendages is secured to the end of this shaft. Under it are the usual spaces for laying off or indicating the proper number of index holes for the required fraction of a circle the spindle is to be moved through. The spindle is hollow and has a screw on the outer end for taking a chuck or face plate. It has a taper hole for receiving the proper centre, which carries a lug for holding the dog used when the work to be finished is held between centres. Three index dials, which are made interchangeable, provide for most divisions except a few prime numbers to 360.