Fig. 77. Automatic Pinion Making Machine of the
Davenport Machine Company.
The Slide Gauge Lathe.—The system of turning with the slide gauge lathe, formerly adopted for lantern pinions in the clock factories, would seem to the watchmaker of a peculiarly novel nature. The turning tools are not held in the hand, in the manner generally practiced, neither are they held in the ordinary slide rest, but are used by a combination of both methods, which secures the steadiness of the one plan and the rapidity of the other. Adjustable knees are fastened to the head and tail stocks of the lathe, Figs. [75] and [76], which answer the purpose of a rest; both the perpendicular and horizontal parts of these knees being fastened perfectly parallel with the centers of the lathe. A straight, round piece of iron, of equal thickness, and having a few inches in the center of a square shape, mortised for the reception of cutters, is laid on these knees, and answers the purpose of a handle to hold the cutting tools. Two handles will thus hold eight tools, one set for brass and one for steel. On every side of the square part of this iron bar, or what we will now call the turning tool handle, a number of cutting tools are fastened by set screws, and the method of using them is as follows: The operator holds the tool handle with both hands on to the knees that are fastened to the head and tail stocks of the lathe, with the turning tool that is desired to be used pointing towards the center, and it is allowed to come in contact with the work running in the lathe in the usual manner practiced in turning. [Fig. 76] is from a photo furnished by Mr. H. E. Smith of the Smith Novelty Co., Hopewell, N. J., and shows the tools in the rack, which is wound with leather so that the tools may be rapidly thrown in place without injury.
Fig. 78. Showing Successive Steps in Turning on
Automatic Pinion Making Machine..
If a plain, straight piece of work is to be turned, the tool is adjusted in the handle so that the work will be of the proper diameter when the round parts of the handle come in contact with the perpendicular part of the knees or rest; and while the handle is thus held and moved gently along in the corners of the knees, with the tool sliding on the T-rest, the work is easily turned perfectly parallel, smooth and true. Sometimes a roughing cut is taken by holding the bar loosely and then a finishing cut is made with the same tool by holding it firmly in place. In turning a pinion arbor, for instance, the wire having been previously straightened and cut to length and centered, and the brass collets to make the pinion and to fasten the wheel having been driven on, one end is held in the lathe by a spring chuck fastened to the spindle of the lathe, while the other end works in a center in the other head. One turning tool is shaped and adjusted in the handle for the purpose of turning the brass collets for the pinion to the proper diameter, another turns the sides of the brass work, while others are adapted for the arbors, pivots, and so on, pins being placed in holes in the T-rest to act as stops for the tools. After the brass work has been turned, the positions of the shoulders of the pivots are marked with a steel gauge, and by simply turning round the handle of the turning tool till the proper shaped point presents itself, each operation is accomplished rapidly, and the cutting is so smooth that even for the pivots all that is necessary to finish them is simply to bring them in contact with a small burnisher. The article is not taken from the lathe during the whole process of turning, and when completed the centers are broken off, having been previously marked pretty deep at the proper place with a cutting point. Five hundred to 1,200 arbors per day, per man, is the usual output. All the pinions, arbors, and barrels—in fact every part of an American clock movement that requires turning—were formerly done in this manner, at long rows of lathes in rooms, and by workmen set apart for the purpose. But perhaps it may be well to mention that in the machine shops of these factories, where they make the tools, the ordinary methods of turning with the common hand tool, and by the aid of ordinary and special slide rests, are practiced the same as it is among other machinists. In the large factories automatic turret machines are now coming into use and these are shown in Figs. [77], [78] and [79].
