Interchangeability Old and New.
The cheap duplication of products, so wonderfully expanded of late years, had its germ long before the Christian era, when in Babylonia a builder first made bricks in a mold, and took care by careful measurement to keep to uniform dimensions in his output. Because any brick matched any other from the same mold, he introduced a new beauty and regularity in architecture, he made it easy to extend or repair a wall, a gateway, a battlement. So it was afterward with the tiles, also made in molds, which were laid as floors or roofs; and the piping, likewise molded, for water-supply or drainage. To-day when a housekeeper replaces her worn-out stove-linings, and a printer increases his stock of type, they enjoy a direct inheritance from the first molders of bricks and tiles, cups and bowls. In a modern factory vast sums are expended in producing the original patterns, molded or copied perhaps ten million times, so that their cost, in so far as represented in each manufactured hook or lever, is next to nothing. Much expense, also, is entailed in making the jigs which guide the tools used in lathes or milling machines to turn out the cases of voltmeters, or a complicated valve-seat. A jig may cost a hundred dollars and its use may require rare steadiness of hand, the utmost keenness of eye; all the while the operator’s wife, at home, avails herself of an aid based on the very same principle. What else is the paper pattern according to which she cuts out a collar, an apron, a baby’s bib?
In machinery the first introduction of an interchangeability of parts was by General Gribeauval, in the French artillery service, about 1765. He reduced gun-carriages to classes, and so arranged many of their parts that they could be applied to any carriage of the class for which they were made. These parts were stamped, not forged. The next step in this direction was taken in America and, as in France, its aim was to improve instruments of war. Eli Whitney, famous as the inventor of the cotton gin, secured a contract from the United States Government for 10,000 firearms. These he manufactured almost wholly by stamping. He introduced machinery for shaping and, as far as then feasible, the finishing of each part. He also employed a system of gauges, by which uniformity of construction was assured for every gun produced. Next came J. H. Hall, of Harper’s Ferry, Virginia, who in 1818 made every similar part of a gun of such size and shape as to suit any other gun, improving some details of importance.
Flat jig, or guide.
The modern designer of tools, implements and machines takes care that the parts upon which wear chiefly comes are easily removable so as to be cheaply replaced. A worn out plowshare is renewed for a dollar or two, keeping the plow as a whole substantially new. Should the pinion of a watch be destroyed by accident, it is duplicated from Waltham or Elgin for a few cents.
To-day rods, wires, screws, bolts, tubes, nails, sheets of metal, are made in standard sizes. Much the same is true of rails for railroads, girders, eye-bars for bridges, and the like. Thus the product of any factory or mill may be used to piece out or to repair work turned out by any other similar concern. Yet more, if a subway or a tunnel is to be built in a hurry, two or more steel-works may co-operate in furnishing beams, columns, or aught else, with no departure from ordinary gauges. Steel works in Pennsylvania have produced every detail for a bridge erected in Africa, a factory in Germany, a stamp mill in Canada. At the World’s Congress of electricians held in Chicago in 1893, units were adopted as international standards, a noteworthy step toward adopting universal standards in all branches of engineering. Here progress is to some extent held back by firms and corporations that produce patterns not always worthy of defence. Standard forms and dimensions, especially in manufactures for a world-market, are only decided upon after thorough discussion, so that they are judiciously chosen. Among feasible shapes and sizes for rails, columns, girders, and the rest, one is usually best, or a few are best. Why not exhaust every reasonable means of ascertaining which these are for specific tasks that they may be freely chosen? Then if individuality prefers its own different designs, let it do so knowing what the indulgence costs.