plished fact. We may now go ahead and manufacture by means of the interchangeable system, which allows of the construction of machinery at the minimum of cost and to the maximum of production; and, what is more, allows of constructing machines in exact duplication of each other, which could not be accomplished by any other means.

THE AMERICAN TOOL-MAKER-THE MOST SKILLED MECHANIC IN THE WORLD.

When all the skill, capacity, and brains utilized in the accomplishment of the mechanical results outlined in the foregoing are considered, is it irrelevant to make the assertion that the genius and intelligence utilized in the inventing, developing, perfecting, and manufacture of machinery are second to none and above most? We think not; and if any one who doubts the truth of it will stroll through a modern machine-shop, of the kind necessary to the production of intricate, labor-saving machinery, and notice the various operations through which the parts used in the construction of such machinery go, and the special tools, fixtures, appliances, arrangements, devices, and machinery used for their production, we think he will change his mind and will be grateful that America and Americans can boast of men who are capable of such things; for it is to such as they, more than all others, that we owe our commercial and industrial supremacy of to-day. The great changes in the last century, which have contributed to the uplifting and betterment of the human race, are marked by the achievements of men whose whole lives and energies have been devoted to the perfection and production of things mechanical. This genius of invention which has conceived, developed, and made possible the manufacture of labor-saving machinery, has multiplied and improved the necessaries as well as the luxuries of life.

We are known and acknowledged to-day as the greatest world power. What has made us so? It is to those who have developed and perfected our modern manufacturing industries that we owe the most. It is because we can view with equanimity the strivings of other nations to outdo us; because we can go out into the markets of the world and meet and overcome their com

petition, that we are what we are. And how has this come about? Simply through the great inventive ability and ingenuity of American engineers and mechanics. Thus has the production of all articles and necessaries of commerce been cheapened and multiplied. Go into the drawing, construction, or tool department of any of the large machine establishments and note the men employed therein. They will be found to bear favorable comparison with those engaged in any of the other arts or professions. What is more, these men do not stand still, but keep increasing their knowledge, and thus step higher and higher to positions which their ambitions and capacities entitle them. From the ranks of such men come the best of our inventors of machinery, our superintendents and managers.

Before closing this introductory chapter, I will say the industrial supremacy of the United States in the twentieth century has come about through the developing and perfecting of the modern system of interchangeable manufacturing, and will ever stand as a monument to the skill and ingenuity of the American mechanic.

CHAPTER II.

Machine Tools, Designing, Tool-making, and Tool

Rooms.

MACHINE TOOLS.

IT has been well said that the foundation of the industrial structure of to-day rests on machine tools; and with this statement, I believe, all who are familiar with the mechanical development of the last decade and have given any thought to industrial betterment will agree. It is a fact, that all must now concede, that without these machine tools, these wonderful factors in modern civilization, we would be reduced to the state of primeval man and be forced to do by hard physical labor that which thousands of automatons now accomplish for us. It is with machine tools that all other machinery is produced; the standard tools of the universal shop, the lathes, drills, planers, shapers, millers, boring-mills, and the numerous minor members of the great family, are all called upon to contribute their share to further economic modern manufacturing.

Now, in view of the afore-mentioned facts, it must be obvious to all that the nation which aims to lead in industrial matters must be the one that possesses the most efficient and best developed machine tools, as the possession of such is a criterion of the mechanical skill and ingenuity of the country's mechanics. Hence where the best machine tools are found there will also be found the best knowledge of how to operate them to the best advantage. Thus we arrive at the conclusion that if good tools are to be made, a comprehensive and broad knowledge of how tools should be used and the amount of work they should do is absolutely essential. Of those who are possessed of this knowledge, it may be said that they are indeed ornaments to their profession, as they stand equipped to produce means which will lighten the load bequeathed by Mother Nature to both man and beastmeans for doing the world's work economically and efficiently.

THE DESIGNER.

When considering machine tools we are at once confronted by the fact that the efficiency of any machine, device, arrangement, or tool used in manufacturing is determined solely by the quality and quantity of its output. To some extent this is modified by the skill of the workman using the machine or tool. However,

machines and tools should be designed and constructed so that the factor of skill in handling will be ineffective except in contributing to produce a better quality or a greater quantity of work than is demanded in the specifications.

Now in order for the designer to be capable of designing a machine or a tool which will meet modern requirements, he must first be thoroughly practical and familiar with the details of the various lines of manufacture in which his creation is to be employed. A theoretical knowledge of the properties of all materials, under all conditions, must also be possessed by the man who wishes to accomplish things in tool design, before he can hope to solve the innumerable problems which will confront him. When the vast field to be covered is considered, it is plain to all that the task that is set is no ordinary one and that his mental equipment must be very complete in order for him to succeed. It is well that the comparatively limited number of methods employed in the working of metals contribute somewhat to the lightening of his load. These methods may be enumerated as follows: forging, rolling, pressing, turning, drilling, tapping, planing, milling, grinding, punching, shearing, and sawing. This list comprises the most important methods; the rest are minor and may be virtually classified under some one in the above-enumerated list.

THE GREAT PRINCIPLE OF REPRODUCTION.

The designing and constructing of fixtures and special tools to be used in machine tools for modern manufacturing represent the highest application of the great principle of reproduction. It is this subject that we are about to take up, and it comprehends not only the tools known as jigs and fixtures, but all special tools of various types which are in general use to-day for the

cheap and accurate production of parts in duplication and repetition, whether of metal or other material. The inception of the grand principle may be traced back almost to the beginning of time.

Perhaps the earliest application of the principle of reproduction was in the moulding of plastic materials which were afterwards baked. From the days of the first use of moulds to the application of the principle in the art of printing was a long step, yet it was in that art that it next found use in printing from hand engravings and afterwards from removable type. Following this, the principle was applied in the making of reproductions of paintings and lithographs, in the coining and stamping of metals, and then in the casting of metals and numerous other materials. In fact, I might go on for pages and trace the application of the principle of reproduction down to to-day, and at length stop at a set of tools for the repetition production of a modern universal milling-machine or a precision-lathe.

The most advanced application of the principle of reproduction in which we are interested is to be found in the use of templets, gauges, jigs, fixtures, and cradles, as those tools are chiefly used in working and cutting parts of metal, to a limited degree of variation, which have been previously roughly formed by the processes of rolling, drawing, forging, or casting.

FUNCTIONS OF JIGS AND FIXTURES.

In jigs and fixtures their functions are often combined with those of machines in which they are used, such as a machine of special design fitted for operating on parts of the same size and shape, the work being located and the tools operated by devices self contained in the machine. This we find in a multiple spindle drill, which has been specially equipped for drilling all holes in a part of a machine or in a large plate, the drill-spindle cases being rigidly fixed in position in a certain relation to each other. In a machine of this type the position of the drill spindles represent the jig, as it is only necessary to place the work on the table and the holes may be drilled in the same position as those in the preceding piece.

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