THE DRAWING AND FORMING OF DECORATED SHEET-METAL ARTICLES.

Then make your trial When the exact blank

By far the greatest development in dies for the drawing of sheet metal has been along the line of decorated tin boxes. The fundamental practical points to be kept in mind when constructing dies for working such stock are as follows: Make three templets-one for the drawing die, another for the drawing punch, and a third for the corners, so as to get them the proper radius. Finish the drawing die, the punch plate, the two sides of the blank-holder ring and the inside of it, and the drawing die, before starting on the cutting die or punch. draws until the proper blank is found. has been found, finish the cutting die and the outside of the blank-holder ring, and fit the blanking punch. Take a cut off the die base after the die has been hardened-this base should be, of course, of mild steel. For decorated metal allow about .006-inch clearance in the drawing die; that is, finish the drawing die .006-inch and two thicknesses of metal larger than the drawing punch; while for plain tin allow about .0035-inch clearance in the drawing die. By giving this clearance there will be no necessity for easing up with files or scraping or grinding, and the designs on the metal will not be marred or scratched. Round the edges of the drawing die smoothly; if the draw is very short, 3 inch will be enough, and if long, increase it accordingly. Be careful to get all the corners of the drawing punch the same radius and those in the die also (plus two thicknesses of metal and the clearance) and lap very smooth. By keeping the foregoing points in mind no trouble will be encountered when con structing a die of this type or in using it either.

"FINDING" THE BLANKS FROM WHICH TO DRAW SHELLS.

The finding of the proper size blank for drawn shells is usually a troublesome matter; however, the way to figure out the approximate size of a blank for a straight cylindrical shell is as follows: Take the outside diameter of the shell to be drawn and

add to it the length or depth of same.

Then add to this inch for every inch of depth, and the resulting total will be very near the exact size of the required blank. For deep shells this rule will allow of finding a blank which, when the shell is drawn, will leave enough for trimming; while for shallow depths, which will draw perfectly straight across the top, a slight reduction in size will be necessary. The amount to deduct will become apparent after the first trial draw.

There are any number of rules for figuring the side of blanks, in which the principle upon which the finding of the diameter is based is that the area of a drawn shell equals the area of the blank from which it is drawn. But as this is never the case, because of the fact that all metals stretch and run unevenly under drawing pressure, the rules work well only on paper. The way to construct a drawing die in the shortest possible time is to figure out the approximate size of the blank in the manner described in the foregoing; cut out and file up a templet according to the result; make the drawing portions of the die; make the trial draws; discover where there is an excess or a deficiency of metal; make a new templet, which should be almost perfect, draw it up, and if found correct finish the cutting portions of the die.

CHAPTER XXV.

The Making and Use of Punches and Dies for SheetMetal Working.

HAVING in the preceding chapter presented the fundamental principles and practical points which are necessary for the toolmaker to know in order to construct and use dies successfully, I will devote this chapter to describing and illustrating the various types of dies in general use. The designs have been selected as representing the most advanced practice in the best shops, and may be adopted, with slight modifications, in dies for the production of sheet-metal parts and articles in endless varieties.

The number of dies shown in this chapter and the one following is sufficiently large, and the variety representative enough, to allow of the reader comprehending all types. When, in the case of the descriptions, it has been found expeditious to describe means and ways for constructing, this has been done. In fact I have adopted this method all through the book; for I do not think it is enough merely to illustrate the tool; the mechanic is also interested in the manner in which it should be made and how the desired results may be accomplished.

THE MAKING AND USE OF SIMPLE DIES.

I will first show and describe a number of dies that are invaluable for use in the average machine-shop, especially the jobbing tool-shop. The dies shown are the most simple and inexpensive of their class for work of the kind shown. Fig. 436 is known best among die-makers as an emergency die—that is, a punch and die for producing a small number of blanks of a given shape and size, of which the blank X is an example.

The die A consists of a piece of-inch flat tool steel, planed and fitted to the bolster, with the shape of the blank worked out at B B. In dies of this kind, when only a small quantity of

blanks are to be punched, the clearance or taper of the die from the cutting-edge is considerable, as the more clearance given the less work and skill required to finish, allowing the blank just to fit at the cutting-edge. This die is hardened and drawn. For the punch a cast-iron holder Cis turned and finished and faced flat and smooth on the front. The punch D consists simply of a piece of 4-inch flat tool steel worked out and sheared through the die and left soft. It is then hard-soldered to the face of the holder C. For punching blanks from thin sheet metal to the number of 10,000, this die is all right. Although some may say

"a botch job," the results will be found to be all that is required. This style of die is used universally in almost all of the fancy sheet-metal goods houses, as the number of different shapes, and the small quantities required, necessitate the elimination of all unnecessary expense.

The die shown in Fig. 437 is known as a shearing or finishing die for heavy blanks and is used for finishing work such as is often done in the milling-machine, or grinder. The blank Z, as will be seen, is a small handle punched from -inch mild steel. In punching for heavy blanks the punch is always fitted very loosely to the die, and the blank produced is generally concave at the edges, and has a ragged appearance where it has cut

away from the rest of the stock. To remove these defects and marks, the blank is sheared through the finishing die, Fig. 437, when trimming or cutting off a shaving of stock all around, the blank leaves it smooth and has an appearance of having been milled. In making dies of this kind one of the blanks that have been punched is taken and filed and finished all around the edges, removing about .003-inch of stock all around. The blank is then used as a templet for finishing the die, letting it through from the back and filing the die straight, with just the slightest amount

of clearance, being sure to have the blank a good fit at the cutting-edge. The inside of the die is then finished and polished as smooth as possible at G and then filed taper downward from H. I is the gauge plate which is worked out and finished to allow the rough blank to fit nicely within it. The plate is fastened to the face of the die by the screw J and the dowels K, so that the blank will rest on the face of the die I with an equal margin all around for trimming. Great care should be taken in adjusting this gauge plate to its proper position, as the small amount of stock to be trimmed will not allow much leeway. The die is