up in the shaper or keysetter, and four grooves are planed in the inside, parallel with the taper, to prevent the babbitt lining from turning.

We now rough-turn the plunger 2, back-rest it, and then bore it for the punch piston; after which it can be threaded for the

Plunger

Sub-Press

+

FIG. 549.

Slide Hook

nut 5. This nut should be made of machinery steel, and have two flats milled on it at o o, so as to be able to remove it from the plunger. With this nut well screwed down the plunger should be turned to within about .005 inch of the finish size, and then finished by grinding, making sure to have it perfectly parallel ; after which it should be placed in the miller vice, and four grooves milled in it, being sure to have the miller vice exactly in line; if the vice is slightly "out" a twisting motion will occur in the plunger when in operation in the press, and this will, of course, spoil the dies. Now we draw-file the plunger, using No. 2 emery stick, which will give better results than a file, and then all is ready for the babbitting. We get the babbit at the right heat, pour it, and allow it to rise about inch above the top of the stand.

As soon as the stand has cooled enough to handle, the plunger should be forced down far enough to allow the babbitt to be faced and squared off on the end, and the thread cut on the end of the stand or nut 4. Now remove the plunger from the stand, and locate the stand in the lathe again; then cut a spiral oil groove of about 1-inch pitch in the babbitt lining. The stand

and plunger should now be secured in the power-press, and pumped, using plenty of oil, and tightening down the nut occasionally so as to get a good bearing. It must be watched at this stage, in order that excessive friction may not heat the babbitt lining sufficient to cause it to swell, and thus destroy the stand. Now reface the stand in the lathe, and face the bottom and bore the seat about 2 degrees taper to fit over the taper boss on the

base. The plunger may now be removed from the stand, backrested, and recessed for the dies. The base can then be located on the face-plate of a lathe-having previously planed the bottom-and the boss turned 3 degrees taper to suit the stand; also recess it for the dies and lower stripper, after which it can be drilled and counter-bored, and then doweled to secure the perfect alignment of the two sections.

SETTING AND WORKING A SUB-PRESS.

The sub-press can be worked in almost any power-press of suitable space. However, usually, a special press is used for the purpose, as a short stroke and a stiff arch-framed press best meet the requirements; Fig. 549 shows a press of this kind.

To set a sub-press, simply slip it into place, as shown in Fig. 549, by sliding the steel neck of the plunger into the press-slide hook, and then locate the hold-drawn clamps into their places and tighten the screws or nuts, thus fastening the sub-press firmly to the bed of the power-press or bolster plate. The dies

may now be set and all is ready to proceed with the punching. The changing of a sub-press is very quickly done, as no special skill is required. There are several different styles of sub-press frames; the most common is the round barred-arch shape. An overhang pattern is often used. For the very largest work, such as clock or time-register frame backs, a four-pillar subpress, which cuts quite large blanks from stock as thick as inch, is used. The manner in which the punching in a subpress is done must not be confounded with ordinary punching, as it is done in a different manner. As a rule three or more operations are performed at one stroke of the press-that is, cutting the outside, cutting the centre, perforating the blank, and lettering it all at once. The stock to be punched is securely held between the stripper plates and pads; thus the die is compound; thus the metal is straightened and held perfectly flat while being worked upon, and each and every piece produced is an exact counterpart of the one previously cut.

ACTION OF THE DIES-FEEDING OF THE METAL.

In the production of the most accurate classes of work in the sub-press, the punch does not enter the die proper, but descends within a shade of its face, thus parting the blank from the stock, and no more; the strippers flatten its edges out square. It must be understood, though, that the die and punch faces must be perfectly flat and without any shear in order for the work to be produced accurately; for this reason a stiff, well-made press is required. Because of constructing the dies in this manner their longevity is greatly extended, as the punches merely pass through the comparatively soft stock and not in and out of the hardened dies, which would shear and wear them quite rapidly. Never, under any circumstances, allow the punches to enter the dies, as this will spoil the tools in a short time.

As the sub-press is a small, convenient machine in itself, with its dies and punches always in perfect alignment, with no possibility of fitting out of order, it is always set ready for work and all chances of bad or inaccurate work are eliminated. While the first cost of this little machine is large, in the long run it is

the cheapest die that can be devised for the accurate and rapid production of perfectly interchangeable sheet-metal parts. It is this little tool that has made possible the manufacture of the "dollar watch."

Roll feeds, or other automatic feeding appliances, are often added to the presses in which these sub-press tools are used. As the articles cut are forced back into their place in the stock from which they were punched by the strippers in the dies, the meta. stock is kept straight and it is punched and accurately fed along under the dies at a very high speed, from 75 to 130 punchings per minute being produced.

CHAPTER XXIX.

Engraving, Sinking, Constructing, and Using Dies for Medals, Jewelry, Coins, and Art Goods.

WORKMAN VS. ARTIST.

THE cutting and engraving of steel dies for the embossing of medals, jewelry, and fine sheet-metal work is an art by itself—an art which, besides requiring mechanical skill and a knowledge of the use of metal-working tools, requires a natural talent for that kind of work and the possession of that artistic ability that comes from the love of things beautiful. Without that ability the die-sinker is merely a workman, and will be incapable of originality it is the talent that makes the artist. However, to those who are already skilled in the art of die-making and who possess to a certain extent the ability to duplicate designs, this chapter will prove greatly instructive; while to those less generously endowed the information contained herein will help them to progress further.

ENGRAVING A HOB FOR SINKING A MEDAL DIE.

In making the dies for medals, etc., the most approved prac tice is as follows: Taking a blank ready to be cut, Fig. 551, we grind the face dead smooth and then either copper it with a solution of sulphate of copper or give it a thin coat of zine white and allow it to dry. We sketch the medallion portion on this surface, as in Fig. 552, and cut away to the necessary depth all the outer sections until a perfect silhouette of the figure is exposed, as in Fig. 553. After this the coarser details are cut in, using small chisels, riffles, and gravers, and boldly rounding all portions which are to appear thus, as shown in Fig. 554. The last and most particular part of the work is to engrave and chase in the fine artistic details until the work appears finished, as in