It is well, in beginning, to define what we mean by the interchangeable system. We will consider it as the art of producing complete machines or mechanisms, the corresponding parts of which are so nearly alike that any part may be fitted into any of the given mechanisms. So considered, it does not include the manufacture of separate articles, closely like each other, but which do not fit together permanently into a mechanism. If this were meant, the work of the early typefounders would clearly antedate that of the modern manufacturers, as they produced printing types by the process of casting which were similar to each other within very close limits. There is, however, a wide difference between this and the parts in such a mechanism as a gun, for individual types are not permanently articulated.

The interchangeable system was developed by gun makers. It is commercially applicable chiefly to articles of a high grade, made in large numbers, and in which interchangeability is desirable. Of the typical articles, such as firearms, bicycles, typewriters, sewing machines, and the like, now produced by the interchangeable system, guns and pistols are the only ones which antedate the system itself. These were used in great numbers, and in military arms especially interchangeability was of the highest value. Under the old system with hand-made muskets, in which each part was fitted to its neighbors, the loss or injury of a single important part put the whole gun out of use until it could be repaired by an expert gunsmith. Eli Whitney, in a letter to the War Department in 1812, stated that the British Government had on hand over 200,000 stands of muskets, partially finished or awaiting repairs.[148] The desirability, therefore, of some system of manufacture by which all the parts could be standardized and interchangeable, was well recognized. There existed a demand for military arms which could meet this condition, but it was felt at the time that it was impossible to meet it.

The system of interchangeable manufacture is generally considered to be of American origin. In fact, for many years it was known in Europe as the “American System” of manufacture. If priority be assigned to the source which first made it successful, it is American; but the first suggestions of the system came from France. We have already seen that the French mechanics were the first to work upon many of the great mechanical improvements; but here, as in the case of the slide-rest and planer, they seem to have caught the idea only. It was left to others to make it a practical success.

At least two attempts were made to manufacture guns interchangeably in France, one in 1717, the other in 1785. Of the first we know little. Fitch, in his “Report on the Manufactures of Interchangeable Mechanisms,” in the United States census of 1880, speaks of it, but says it was a failure.[149] We know of the second from an interesting and surprising source. Thomas Jefferson, while Minister to France, wrote a letter to John Jay, dated August 30, 1785, which contains the following:

Six months later he wrote a letter to the governor of Virginia, which is almost a copy of this one. In another letter written many years later to James Monroe, Jefferson gives the name of this mechanic as Le Blanc, saying that he had extended his system to the barrel, mounting and stock, and stating: “I endeavored to get the U. S. to bring him over, which he was ready for on moderate terms. I failed and I do not know what became of him.”[151] We wish to give full credit to this genius who seems to have caught a clear idea of some at least of the principles involved, those of interchangeability and the substitution of machine work for hand work. The account makes no mention of gauges or of the division of labor, but this might easily have been due to Jefferson’s unfamiliarity with the details of manufacture.

We have seen in a previous chapter that a close approach to the interchangeable system was made in the Portsmouth block machinery of Bentham and Brunel. This was rather an application of modern manufacturing principles than a specific case of interchangeable manufacture. The interchangeability of product obtained was incidental to good manufacturing methods, not a distinct object aimed at, and there does not seem to have been any system of gauging during the processes of manufacture, to insure maintaining the various parts within specified limits of accuracy. In fact, the output itself did not require it, as ship’s blocks do not call for anything like the precision necessary in guns or the other typical products of the interchangeable system.

We have seen, too, that John George Bodmer began about 1806 to manufacture guns at St. Blaise in the Black Forest, using special machinery for much of the work previously done by hand, especially for the parts of the lock, which “were shaped and prepared for immediate use, so as to insure perfect uniformity and economize labor.” In both of these instances, the Portsmouth block machinery and the St. Blaise factory, definite steps which form part of the interchangeable system were taken, but it does not seem probable that the system existed in anything like the completeness with which it was being developed at that time in America.

In 1798 and 1799 two contracts were let by the United States Government for firearms, one to Eli Whitney in 1798, the other to Simeon North in 1799. These contracts are of the greatest importance. Whitney had invented the cotton gin in 1792. This invention, as is well known, had a profound economic effect on the whole civilized world, but the condition of the patent laws at that time and the very value of the invention itself made it impossible for him to defend his rights; and, although he had practically created a vast industry, he actually lost more money by the invention than he gained. By 1798 he made up his mind that he must turn to something else. He chose the manufacture of muskets, and addressed a letter to Oliver Wolcott, Secretary of the Treasury, in which he said:

His contract of 1798 resulted. From the very start Whitney proposed to manufacture these arms on a “new principle.” He built a mill at Whitneyville, just outside of the city of New Haven, utilizing a small water power. Nearly two years were required to get the plant into operation, as he had to design and build all of his proposed machinery. In 1812 when making application for another contract for 15,000 muskets, Whitney writes:

In another place it is stated that the object at which he aimed and which he accomplished was “to make the same parts of different guns, as the locks, for example, as much like each other as the successive impressions of a copper-plate engraving.”[154]

Mr. Whitney’s determination to introduce this system of manufacturing was ridiculed and laughed at by the French and English ordnance officers to whom he explained it. They said that by his system every arm would be a model and that arms so made would cost enormously. Even the Washington officials were skeptical and became uneasy at advancing so much money without a single gun having been completed, and Whitney went to Washington, taking with him ten pieces of each part of a musket. He exhibited these to the Secretary of War and the army officers interested, as a succession of piles of different parts. Selecting indiscriminately from each of the piles, he put together ten muskets, an achievement which was looked on with amazement. We have not the exact date of this occurrence, but it was probably about 1800.[155]

Meantime Simeon North, who unlike Whitney was a gun maker by trade, had completed his first contract for 1500 pistols, and had executed a number of others. In these no mention was made of interchangeability, but whether independently or not, he very soon began to develop the same methods as Whitney. In a letter to the Secretary of the Navy in 1808, North says:

He also says in the same letter:

Here is clearly the principle of subdivision of labor and the beginning of the standardizing of parts. In 1813 North contracted to furnish 20,000 pistols. This agreement contained the following significant clause:

It is stated in the valuable memoir of Simeon North, by his great-grandsons, that this is the first government contract in which the contractor agreed to produce arms having interchangeable parts, and it is consequently claimed for Colonel North that he originated this process.

We have not had an opportunity to examine the official records in Washington in regard to Mr. Whitney’s dealings, but it is quite clear from his letter of 1812 that he had been operating on this basis for nearly ten years, although it may not have been formally recognized in his contracts with the Government. Capt. Decius Wadsworth, then inspector of muskets, wrote to the Secretary of the Treasury in 1800 as follows:

Furthermore, Jefferson, in the letter to Monroe written in 1801, says in speaking of Whitney:

In a letter to the Secretary of War in June, 1801, Whitney writes: “... my system and plan of operations are, I believe, entirely new and different from those heretofore pursued in this or any other country.

“It was the understanding and expectation of the Secretary of the Treasury, with whom I contracted, that I should establish a manufactory on the principles which were then pointed out and explained to him. This system has been uniformly pursued from the beginning.”[160]

It would seem that the stipulation in North’s contract of 1813 was not so much the beginning of a new method as a recognition of methods which had already come into existence. It seems almost inevitable that the two men, pioneer manufacturers and government contractors in closely allied industries, and located but twenty miles apart, must have known more or less of each other’s work and have been influenced by each other’s methods. Without trying to differentiate the credit between them too closely it is quite certain that in the work of these two men the interchangeable system had its birth. Colonel North’s work for the Government was invariably well done, and for more than fifty years he continued to supply, first pistols, and later rifles for the army and navy. Of the two, Whitney had the greater influence in spreading the interchangeable system throughout the country. He was well known and influential through his invention of the cotton gin and was located in a larger center. He was called upon by the Government for advice, and at its request sent to Springfield some of his best workmen to introduce his system there, and also help to start it at Harper’s Ferry. Whitney built his factory in 1798 or 1800, and employed at the start about sixty men. Colonel North moved from Berlin to Middletown in 1813, and built a factory at a cost of about $100,000, where he employed seventy men and produced about thirty pistols a day. The interchangeable system was well begun in both of these factories by 1815.

The Springfield armory had been started during the Revolution, mainly for making cannon. In 1792 Congress authorized the President to establish two arsenals for small arms. These were located at Springfield in the North, and Harper’s Ferry in the South. In 1811 Captain Hall was granted a patent for a gun which was adopted as the government standard in 1819 and the Government undertook to manufacture them at one of its own armories. Captain Hall was placed in charge of the work and the plant at Harper’s Ferry was equipped for interchangeable manufacture.[161] Later many of these rifles were made by private contractors, such as Colonel North. By 1828 in one of Colonel North’s contracts we find the principle of interchangeability extended still further. It is guaranteed that the component parts should be interchangeable, not only in the lot contracted for, but that they may be exchanged in a similar manner with the rifles made or making at the national armories.[162]

In 1836 Samuel Colt invented his revolver, and the first lot contracted for by the Government was made at the Whitney works in 1847. Mr. Colt determined about 1850 to establish his own factory, moved to Hartford, and in 1854-1855 built the present Colt’s Armory, in which the principles of interchangeable manufacture were adopted in a most advanced form. Hand work was practically eliminated and automatic and semi-automatic machinery substituted. A type of manufacturing miller, built for this work by George S. Lincoln & Company, is still known as the Lincoln miller. E. K. Root, superintendent under Colt, had a profound influence in the development of manufacturing at this time. He put the art of die forging on its present basis. At first he used a type of hammer in which four impressions were arranged in four different sets of dies. The hammers were lifted, first by a set of dogs, later by a central screw, and the operator walked around the machine, using the impressions successively. A few years later the present form of board drop was developed. Two of George S. Lincoln & Company’s men were Francis A. Pratt, superintendent, and Amos Whitney, contractor, who later founded the firm of Pratt & Whitney.

In 1857 Smith & Wesson began manufacturing revolvers at Springfield along similar lines. Mr. Smith had worked in the old Whitney shops. Another firm of great influence was that of Robbins & Lawrence, later the Windsor Machine Company, in Windsor, Vt. Frederick W. Howe built there a number of machines for profile milling, rifling, barrel drilling, and is said to have designed the first “universal” miller in 1852.[163] The Ames Manufacturing Company in Chicopee, which had been founded in 1829, was also engaged in this work. By 1850 the interchangeable system began to extend its influence abroad. Robbins & Lawrence had an exhibit of interchangeable guns in the exposition at London in 1851, which attracted much attention. In 1853 a British Commission came to this country and visited the government and private armories, the Ames Manufacturing Company and Robbins & Lawrence. During the visit of this Commission at Springfield, Major Ripley, superintendent of the armory, ordered ten guns, which had been manufactured in ten successive years, from 1843 to 1853, to be stripped, and the parts to be reassembled at random.

As a result of this visit 20,000 interchangeable Enfield rifles were ordered by the English Government, and in 1855, 157 machines for the manufacture of guns were sent to England. These machines comprised seventy-four millers, twenty-three drilling machines, five tapping machines, and seven edging machines. The remainder were special machines for threading, rifling, turning, boring, and so on.[164] In this list of machines scarcely a single lathe is found and no mention is made of any turret machines. Ten or fifteen years later there would have been a large number. James H. Burton, who had been at the Harper’s Ferry armory and was at the time with the Ames Manufacturing Company, went over to England to install the new system and operate the new plant. The Ames Manufacturing Company alone is said to have exported four to five hundred stocking machines of the Blanchard type on these early foreign orders. Within the next fifteen or twenty years nearly every government in Europe was supplied with American gun-making machinery, all planned to operate on the interchangeable system, which was known everywhere as “the American system.”

Nasmyth was concerned in the introduction of this machinery into England. His mention of it in his autobiography throws light on how the interchangeable system was looked upon by the English engineers:

In using the term “interchangeable” it must be remembered that the meaning attached to this word grew during these years. The interchangeability of 1813 would not have been considered satisfactory in 1855, much less so today. When Hall completed his first hundred rifles at Harper’s Ferry in 1824, it is said that “the joint of the breech block was so fitted that a sheet of paper would slide loosely in the joint, but two sheets would stick.” This system of gauging will have a familiar sound to the older mechanics who grew up before the days of the micrometer. When Colonel North was given his first contract for the rifles and furnished two models to work from, these models were so unlike that he asked to have one set aside and that he be allowed to gauge his work from the other.

Of the various tools associated with interchangeable manufacture, drilling jigs were in use very early, probably from the start. The filing jig is said to have been invented by Selah North, the son of Colonel North, but it was used by Whitney almost as early. Both Whitney and Colonel North were using plain milling by 1820. A light sort of milling machine is shown in the French Encyclopedia of 1772, already referred to, but the first successful one was built by Mr. Whitney some time prior to 1818. This machine, still in existence and now in the possession of the Sheffield Scientific School of Yale University, is shown again in Fig. 28.[169] In 1817 to 1822 we find the introduction of forging in hand dies, barrel turning by special machinery, and the Blanchard lathe for gun-stocks. Receiving gauges are said to have been used at Middletown in 1829, and were regularly in use at Springfield by 1840. Automatic machinery for the woodworking was first invented by Blanchard in 1818 for the Springfield armory. The accuracy of these machines, shown in Fig. 29, outran that of the metal work of the time. To accommodate the variations still present in the metal parts Blanchard devised a machine which used the actual lock plates as formers and cut the stocks to match, and such machines were used at Springfield until 1840. By that time the work on the metal parts could be made as accurately as the stocks, and this method was no longer necessary. A modern degree of accuracy in shaping of the metal portions was not possible until the miller came into general use for irregular shapes, which was some time in the forties. By 1842, for the new musket to be manufactured at Springfield, there was a complete set of model jigs, taps and gauges. The profiling machine was developed by F. W. Howe, R. S. Lawrence, and E. K. Root, from 1848 to 1852. A drop hammer with dies was used by Hall of Harper’s Ferry in 1827, the head of which was raised by a moving chain and freed by a trip at the desired height. Later Peck invented his lifter, using a strap. The Root drop hammers we have already mentioned. The board drop is largely the work of Spencer.

Probably no machine has had so great an influence on interchangeable manufacture as the automatic turret lathe. The turret lathe, “the first radical improvement on Maudslay’s slide-rest,” was built commercially by Robbins & Lawrence in 1854, and is said to have grown out of a revolving-head bolt cutter which Henry D. Stone saw at Hartford. The turret idea was not originated by Stone. Root and Howe had used it a number of years before, and it had been utilized by several others. All of these turrets except Howe’s seem to have had a horizontal axis instead of the vertical one which became general. Later improvements by C. M. Spencer and a long line of brilliant mechanics have increased the accuracy of the turret lathe and made it more nearly automatic than any other type of general machine tool. Today it is, with the milling machine, the main reliance for interchangeable work.

In sketching the development of interchangeable methods in American shops, we have confined our attention to gun makers chiefly. They were by no means the only ones to have a part in this development, but they were its originators, they determined its methods, and developed most of the machines typical of the process. About 1830 Chauncey Jerome began the manufacture of brass clocks. Terry, Thomas and other Connecticut mechanics had been manufacturing wooden clocks, which gave way to metal clocks as the advantage of interchangeable manufacture became recognized. In 1848 A. L. Dennison founded the American Watch Company at Waltham. The interchangeable system has nowhere reached a higher development than in the work of this company and of the other great watch factories. In 1846 Elias Howe was granted his patent on sewing machines, and within four or five years their manufacture sprang up on a large scale. Both of these industries, watch and clock manufacture and the manufacture of sewing machines, utilized a system which was already well established. Since that time it has been applied to a wide variety of articles.