INTRODUCTORY

VERY little of value has been written on drop-forgings, die-sinking, the machine-forming of steel, and the shop practise involved, as it actually exists in the modern drop-forging shop. Here and there, a solitary die or device has been pictured and described, or a few sketches made of dies that may have been entirely imaginary, so far as can be learned from any evidence offered, and which are of such simple and elementary nature as to convey no adequate idea whatever of the magnitude and difficulty of the work to any one not familiar with it. This class of contributions covers the greater part of what has been published on a subject that has grown and developed from the hand-forging process of the hammer and anvil, to one of the most important branches of modern machine industry.

Hundreds of parts that were formerly cast from malleable iron, or hand-forged from bar stock, are now drop-forged, the extra cost being more than made up by the uniformity, strength, and reliability of the product; and no one has been quicker to realize this than the really live, up-to-date automobile manufacturer, to whom the mechanical world is indebted for so many other valuable mechanical developments.

The history of die-sinking and drop-forging goes back fifty years or more in New England. In the blacksmith-shops of the original "Yankee Toolmakers," a limited amount of work had been previously done in dies for as long a period, but only or chiefly in order to impart a "finish" to work which had been already hand-forged and nearly completed at the anvil. This practise was necessarily adopted in order to attain uniformity, in a number of similar forgings, economically. Such uniformity could only be produced on the anvil

with the common tools of the smith, at the sacrifice of much time and labor. Hence, long before the practise of producing forgings by drop-dies or machine forging, comparative interchangeability was eventually attained in anvil-made forgings by means of dies used in the power-hammer. The dies, even then, were often in sectional form, as they remain to-day when heavy forgings are required.

The making of drop-forging dies, together with the hardening process through which they are put and the methods of using them, is a trade by itself, though closely allied to tool and die making as understood in the big shops of to-day. Each branch of shop-work presents its individual problems, and a tool and die maker, though skilled in other lines, cannot go into a forging-shop and make dies without special instructions, training, and a knowledge of the practise involved.

In drop-forging die-work, as in other kinds of tool-work, there are various grades of accuracy and finish required. Some forgings must come from the hammer practically finished to size, while others are made large enough to allow considerable machining. Where only a few pieces of rough nature are required, little skill is needed in making or maintenance of the dies, but where small, accurate parts are to be made in large quantities, special tools for both hand and machine use are necessary, and trained, skilful diemakers are needed, as well as a careful selection of the steel used.

The employment of drop-forging and the production of hot and cold pressed parts of the nature referred to in the foregoing, are increasing constantly and rapidly. A large number of firms are now equipped with machinery used exclusively for this class of work, and they supply enormous numbers of forgings to manufacturers of metal-working machinery, automobiles, railroad-cars, car-parts, and innumerable users of metal parts.

Drop-forgings and pressed metal parts bear the same relation to the work of the blacksmith-shop that machine-molded castings bear to that of the foundry. In both cases, the skilled

mechanic and his labor are dispensed with. In each instance the finished product has the advantage of much greater accuracy and uniformity in shape and dimensions. The numbers turned from the dies, as from the molding machines, are often thirty to forty times as great as those which are produced by hand by skilled men. In both cases, too, the question of machining is often inseparable from that of the methods of production adopted, because accuracy of shape and uniformity of dimensions in forgings and castings alike are favorable to the most economical machining, since allowances which are either insufficient or excessive for the machines are equally undesirable and troublesome. The blacksmith working at the anvil, even with the help offered by templets and gages, is unable to produce two pieces-to say nothing of twenty intricate and elaborate pieces-absolutely alike, unless at an enormous expenditure of time. It is cheaper, therefore, and is the practise to leave plenty of surplus surface stock to insure that the work shall finish up all over when machined; otherwise the final finishing would occupy much time, even more than that required for the formative work of forging. But forgings which are dropped or machine finished-that is dropforged-all come exactly alike from the dies; and interchangeability to the desired degree is attained in the initial process, without extra care or time spent on the part of the workman. Moreover, since the allowance, or surplus stock left, is small in amount and regular, pickling can be more usefully practised than when allowances are excessive.

The accuracy of forgings-machine and die producedhowever, is further advantageous in the fact that a considerable amount of machining is often avoided altogether. The smooth, glossy, polished, and accurate surfaces left from the dies are often good enough for handles, levers, and numerous other parts. Or if they are required to be polished bright for good appearance, then a polished surface imparted by emerywheel, buff, or tumbling barrel is sufficient, without any more machining in the lathe, shaper, or milling machine. Punched holes may be simply lapped, instead of being

drilled and reamed, the locations of the holes being fixed with accuracy by the dies.

The process of die-sinking relates to the engraving or sinking of the female or lower dies, such as are used for dropforgings, hot and cold machine forging, swedging, and the press working of metals. The process of force-making relates to the engraving or raising of the male or upper dies used in producing the lower dies for the press-forming and machineforging of duplicate parts of metal.

CHAPTER I

DIE-SINKING AND DROP-FORGING PRACTISE AND DESIGN FOR MODERN FORGING, PRESSING, AND STAMPING OF DUPLICATE METAL PARTS

DROP-FORGE WORK

Materials for, and Life of, Drop-Forging Dies

STEEL, cast into blocks, is not suitable for drop-forging dies, as flaws or blow-holes are likely to develop where least expected or desired; so, as a general rule, forged blocks of open-hearth crucible steel are used. These blocks are either purchased ready forged, in various sizes, from the steel manufacturers, or are forged in the shop where they are usedthe former plan being the usual one.

A rough estimate as to the average life of a drop-forging die, used for medium-sized work on Bessemer steel, is given by a foreman of long experience, as about four thousand pieces. Some dies might be broken immediately when put in operation, while others might stand for a hundred thousand pieces or more.

Automobile Shop Drop-Forging Practise

The Figs. 1 to 22 and the data relating to them were obtained in the factory of Thomas B. Jeffery & Co., Kenosha, Wis. This company's drop-forging plant is far ahead of anything outside of the big concerns that make a specialty of drop-forgings, and consists of a well-lighted, finely equipped tool-room, used only for drop-forge die-work, a thoroughly up-to-date hardening plant, and a big building full of steamhammers, punch-presses, heating furnaces, and every appliance necessary for first-class work.