CHAPTER XXVI.

The Making and Use of Punches and Dies for
Sheet-Metal Working.-Continued.

A PUNCHING AND CURLING JOB.

IN Fig. 471 are shown the results of successive operations in the production of a sheet-metal part of unusual shape which formed part of a patented apparatus.

The upper diagram in Fig. 471 shows the results of the first and second operations. The holes in the ends were punched, the

ends were shaped, cutting off the piece, and twenty-nine slots along one side were punched.

The piercing of the holes, shaping the ends, and cutting off the pieces were done in the first operation by the punch and die shown in Fig. 472. The work in this operation is all at the ends, necessitating a punch and die of different construction from those usually used. In the die section the die for piercing and that for cutting off and end-shaping are dovetailed into the face of the cast-iron bolster, one at each end, and secured by taper dowelpins. The gauge-plate extends along the entire length of the bolster, and is fastened to the die faces with the stripper plates by flat-head screws. The stripper plates are made of extra heavy stock and are worked out so that the punches are supported while doing their work. In the punch section the construction is similar to that followed in the die section, in that the cutting

off and end-finishing punch is dovetailed into the holder and located by means of a taper dowel; while the piercing punches are let into a pad, dovetailed into the holder, and located in the same manner as the cutting-off punch. The piercing punches

were made of drill rod, hardened, tempered, and of a length sufficient to allow of their always being in the stripper, thus obviating the tendency to bend or snap off. The stock, which required no side trimming, was fed across the die faces automatically. The four holes were pierced at the left, and then the last

end of the piece and the first end of the next piece shaped, and the piece was cut off by the large punch at the right.

For the second operation, that of piercing the twenty-nine slots, a punch and die of intricate and accurate construction were required. In Fig. 473 are shown a front elevation partly

in section, and a vertical cross section, respectively. I illustrate only the punch, as the die was almost identical in construction. The punch section consists of, first, a cast-iron holder C, then a supplementary punch-holder A, the latter in two sections, the twenty-nine punches D, and a spring-actuated stripper H. The spring stripper is left off the plan so that the construction of the other parts may be more clearly understood. The manner in which the punches are located and fastened is unusual. First two pieces A of -inch-thick annealed tool steel were planed to butt together sidewise and then dovetailed into C. These two sections were then clamped together, and twenty-nine slots were milled into them, in depth equal to half the width of the piercing punches. The manner in which the punches were let into these slots and upset at the back, the two sections strengthened by dowels B B, and then driven into the dovetailed channel in the holder, will be understood, as well as that the milling of the slots in the sections A A of the pad was an accurate job. It was accomplished by careful work on the universal milller. The slots were milled about .002 inch smaller than the thickness of the punches. The making of the twenty-nine punches was also a job requiring skill and care. The punches were left over size all over, then hardened between oiled plates and drawn to a dark straw to within 4-inch of the backs, and from there on to a dark blue to allow of upsetting them within the pads at the backs. They were then ground on all sides to size.

The spring stripper plate H H was worked out to fit around the punches rather snugly, so as to give them as much support as possible up to the point where they entered the stock. The faces of the punches were sheared so as to commence to cut at both edges before the centre of the stock was cut away. This is shown in the end view at I.

The die was made in the same way as the pad A A, being in two sections, which were located together by dowels, and were dovetailed into a bolster of the usual kind. Considerable care was required in the hardening of the die section, and in the grinding of the faces afterwards, in order to insure the alignment between the twenty-nine piercing dies and the punches; and although the man who hardened them understood his business and

turned out a good job, it was necessary to peen the edges of some of the pad slots so as to crowd a few of the punches over a thousandth of an inch or so. It was not found necessary to grind all of the dies, although about every third one had to be touched up on the sides with a fine wheel, taking care just to touch the tight spots.

When using the punch and die a blank was located against stops on the face of the die and the press was "stepped." As

the punch descended the spring stripper plate H H flattened the stock and held it securely in position while the slots were being punched. As the punch rose, the stripper forced the work from the punches and allowed it to drop off the die face. After the punch and die had been in use a short time it was found necessary to re-grind the die faces, as some of them had sheared. Then the punches were entered into the dies and solder was run around them at the pad faces. This rendered the alignment perfect, and we had no more trouble.

It will be seen in Fig. 471 that the sections left between the slots punched in the second operation have to be curled alternately, half of them one way and the other half the other way. It was at first thought that a die of considerable intricacy would be necessary; but it was at last decided to do the curling in two operations-but with one die, and that a quite simple one.

FIG. 474.

I show in Fig. 474 a vertical cross-section of the curling die. L is the punch-holder; K the curling punch, located in a square channel in the holder face and fastened by three flat-head screws;

NN are the portions that do the curling, while the cutaway sections E are clearance channels for the sections of the stock which have to be curled in the opposite direction. P is the work, Qa spring supporting pad with the face worked out at O to the radius of the curl; U is a gauge-plate for locating the work against the pad Q; R is the bolster; & the channel in which the spring supporting pad moves, and T one of three spring studs.

The work is placed between the gauge U and the pad Q and against a gauge at the end. As the punch descends, half of the sections to be curled, or every other one, enter the curling grooves N, while the others enter the clearance channels W. The punch continues to descend and the metal follows around the curling grooves until the curls are completed, the pad Q descending with the punch. As the punch rises, the pad Q rises also and carries the work out of the locating slot between the pad and the gauge, and as the punch rises higher it leaves the work free on the top of the pad Q from which it is removed by hand. The fourth operation, curling the remaining sections in the opposite direction, is accomplished in precisely the same

manner.

DIES FOR SHEET-METAL BAG-CLASPS.

In Fig. 475 are shown three views of a patented sheet-metal bag-clasp which was produced entirely by the use of dies, there

being no hand work, except in feeding. The dies here shown are the most interesting ones of the set employed.

The clasp consists of eight parts: the embossed front 4, a