presses in which the work is done is equal to much larger diameters than those used in the method before described.

In producing very large disks there is a great deal of scrap, but this scrap is prevented from going to waste altogether by being worked over into disks of smaller size. From the inside scrap, the projections corresponding to the key notches are re

FIG. 545.

moved by forcing the disk through a circular trimming die which punches the centre hole at the same time, and thus no great waste of stock is entailed.

In manufacturing armature segments in very large quantities the outside and the holes are usually cut simultaneously in dies in which the stripping of the scrap and the segments from them is entirely automatic, for both the upper and lower sections. press specially designed and used for this class of work is shown,

FIG. 546.

equipped with proper tools, in Fig. 547. The cutting of sections and segments complete with dovetails, and all notches and holes up to 35 inches long, can be done on a press of this sort. However, most segments of large size are first punched plain and the notching and perforating are done in succeeding operations.

When the plain segment blanks are not produced in dies, a circular shear of the same type as that used for disk cutting is used; it being equipped with a segment-cutting attachment, as shown in Fig. 545.

In Fig. 546 we have a side view of an armature-segment notching press. The segment-notching attachment on this machine allows of handling segments having a radius of from 36 to 96 inches and up to 36 inches in length. The manner in which

FIG. 547.

the segments are notched is as follows: The segment to be notched is clamped in a holder at the forward end of a long radius bar, and is traversed across the die face by means of an indexing mechanism and change gears similar to those on the regular disk notching press; when the segment is notched all around the outside or inner edge as required, the press stops automatically. After the operator releases a hand lever the segment may be returned to its original position and removed from the press.

CHAPTER XXVIII.

The Manufacture of Accurate Sheet-Metal Parts in

the Sub-Press.

THE SUB-PRESS.

THE great increase in the manufacture of innumerable small machines of precision which are made up almost entirely of sheetmetal parts, together with the increasing demand for cheap but

accurate watches, clocks, time recorders, meters, cyclometers, and other articles, the utility of which depends entirely upon their precision, has created a demand for accurate presses, dies,

feeding devices, and automatic arrangements with which to produce sheet-metal parts in endless repetition with their complete interchangeability assured. For the production of such parts, dies of great accuracy, together with feeding devices which are positive in action, and the sub-press are necessary.

Sub-presses are distinctly different from the other machines which are used for the usual or ordinary lines of sheet-metal work, in that they are made so as to form component parts of the dies, and that they are used almost exclusively for the delicate dies which are required in the economic manufacture of parts of the kind used in the machines, devices, etc., enumerated above.

UTILITY OF THE SUB-PRESS NOT GENERALLY UNDERSTOOD.

Notwithstanding the extensive use to which the sub-press and its accurately made dies have been put, its use and the making of the dies for it are not understood by superintendents, foremen, and tool-makers of sheet-metal goods establishments as they should be. Thus the more extensive use of these tools has been interdicted. Were the case otherwise, and the utility of the subpress and the making of its dies more generally understood, there would be less worry and more satisfaction in the accomplishment of results which, in many establishments, are at present being attained by means which are now obsolete. In view of this state of affairs I feel that complete descriptions of the sub-press, and how to use it and its dies, will be of great value to all engaged in the manufacture of accurate sheet-metal parts, articles, or devices.

PRINCIPAL USE OF THE SUB-PRESS.

The principal use to which the sub-press is put, is for the manufacture of sheet-metal parts which, because of their unusual accuracy, have to be produced in dies which cut the outside and the inside, as well as any perforations, simultaneously, or at least within the one compound die. By the use of the sub-press and its accurate dies the finest work may be accomplished with ease,

as the dies may always be kept finely adjusted for the work; while the enlinement will be perfect, and thus the possibility of shearing will be entirely eliminated.

COST VS. LONGEVITY OF THE SUB-PRESS.

In regard to the cost of a sub-press and a pair of dies for producing an intricate sheet-metal part, the first outlay is considerable; but then this is really all the cost, as the construction of the press is such that no damage can be done to it while it is being set up or run in the power-press; while the dies for it require but little repairs outside of an occasional grinding of the faces. When it is stated that from 50,000 to 100,000 perfectly interchangeable blanks may be cut and pierced in a sub-press without grinding the punch and die faces, the accuracy and longevity of the tools may be imagined.

HOW TO CONSTRUCT A SUB-PRESS.

In order to be able to construct a sub-press or a set of dies for it the tool-maker must be both skilled and accurate, and must use great judgment; possessing these qualities he may, by carefully digesting the following described methods, be sure of suc

cess.

Fig. 548 shows in vertical section and Fig. 549 in plan, a sub-press such as is used in all watch, meter, and cyclometer factories. The sub-press consists of the stand 1, the plunger 2, the base 3, the nut 4, to tighten the babbit lining, and the hook nut 5, which connects the power-press plunger with the plunger 2 of the sub-press. The stand 1 is the first part machined. It is faced and bored on the bottom, and then the barrel is faced and recessed to suit a flange by means of which the plunger 2 is centred at one end for babbitting. The stand is then ready to be drilled and tapped for the fillister head-screws, by means of which it is fastened to the base. These screws are also used to fasten the stand to a special lathe-chuck, by means of which it is bored 3 degrees, taper-faced on the other end, and then turned for the adjusting nut, but not threaded until the stand has been babbitted. The stand having been bored it is then set