THE RISE OF INTERCHANGEABLE MANUFACTURE
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.
[148] Blake: “History of Hamden, Conn.,” p. 133.
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:
[149] p. 2.
An improvement is made here in the construction of muskets, which
it may be interesting to Congress to know, should they at any time
propose to procure any. It consists in the making every part of them
so exactly alike, that what belongs to any one, may be used for every
other musket in the magazine. The government here has examined and
approved the method, and is establishing a large manufactory for
the purpose of putting it into execution. As yet, the inventor has
only completed the lock of the musket, on this plan. He will proceed
immediately to have the barrel, stock, and other parts, executed in
the same way. Supposing it might be useful in the United States, I
went to the workman. He presented me the parts of fifty locks taken
to pieces, and arranged in compartments. I put several together
myself, taking pieces at hazard as they came to hand, and they fitted
in the most perfect manner. The advantages of this, when arms need
repair, are evident. He effects it by tools of his own contrivance,
which, at the same time, abridge the work, so that he thinks he shall
be able to furnish the musket two livres cheaper than the common
price. But it will be two or three years before he will be able to
furnish any quantity. I mention it now, as it may have an influence
on the plan for furnishing our magazines with this arm.[150]
[150] “The Writings of Thomas Jefferson,” Edited by H. A. Washington,
Vol. I, p. 411. New York, 1853.
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.
[151] “The Writings of Thomas Jefferson,” Edited by Paul L. Ford,
Vol. VIII, p. 101. New York, 1887.
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:
I should like to undertake the manufacture of ten to fifteen thousand
stand of arms. I am persuaded that machinery moved by water, adapted
to this business would greatly diminish the labor and greatly
facilitate the manufacture of this article. Machines for forging,
rolling, floating, boring, grinding, polishing, etc., may all be made
use of to advantage.[152]
[152] “New Haven Colony Historical Society Papers,” Vol. V, p. 117.
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:
The subscriber begs leave further to remark that he has for the
last 12 years been engaged in manufacturing muskets; that he now
has the most respectable private establishment in the United States
for carrying on this important branch of business. That this
establishment was commenced and has been carried on upon a plan
which is unknown in Europe, and the great leading object of which
is to substitute correct and effective operations of machinery for
that skill of the artist which is acquired only by long practice
and experience; a species of skill which is not possessed in this
country to any considerable extent.[153]
[153] _Ibid._, p. 122.
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]
[154] Denison Olmstead: “Memoir of Eli Whitney,” p. 50. 1846.
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]
[155] Blake: “History of Hamden, Conn.,” p. 138.
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:
I find that by confining a workman to one particular limb of the
pistol untill he has made two thousand, I save at least one quarter
of his labour, to what I should provided I finish^{d} them by small
quantities; and the work will be as much better as it is quicker
made.[156]
[156] S. N. D. and R. H. North: “Memoir of Simeon North,” p. 64. 1913.
He also says in the same letter:
I have some seventeen thousand screws & other parts of pistols now
forg^{d}. & many parts nearly finished & the business is going on
brisk and lively.
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:
The component parts of the pistols are to correspond so exactly that
any limb or part of one Pistol may be fitted to any other Pistol of
the Twenty thousand.[157]
[157] _Ibid._, p. 81.
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:
But where the different parts of the lock are each formed and
fashioned successively by a proper machine, and by the same hand,
they will be found to differ so insensibly that the similar parts of
different locks may be mutually substituted. The extending of this
principle to all parts of a musket has been a favorite idea with Mr.
Whitney from the beginning. It has been treated and ridiculed as a
vain and impracticable attempt by almost all those who pretended
to superior knowledge and experience in the business. He has the
satisfaction, however, now of shewing the practicability of the
attempt. Although I am of the opinion that there is more to please
the imagination than of real utility in the plan, yet as it affords
an incalculable proof of his superior skill as a workman, and is
what I believe has never been attempted with success before, it is
deserving of much consideration.[158]
[158] Blake, p. 296.
Furthermore, Jefferson, in the letter to Monroe written in 1801, says
in speaking of Whitney:
He has invented molds and machines for making all the pieces of his
locks so exactly equal, that take 100 locks to pieces and mingle
their parts and the 100 locks may be put together by taking the
pieces which come to hand.[159]
[159] See note 150, page 130.
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]
[160] Blake, p. 300.
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]
[161] “Memoir of Simeon North,” pp. 168-169.
[162] _Ibid._, p. 160.
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.
[163] Not to be confused with the Brown & Sharpe universal milling
machine, which was invented by Joseph R. Brown in 1871.
[Illustration:
THOS. BLANCHARD ELI WHITNEY SIMEON NORTH
Blanchard lathe and New Haven, Conn. Middletown, Conn.
stocking machinery After his death Four sons--Reuben,
*1, 2* business carried on James, Alvin and
by E. W. & Philos Selah
Blake, nephews, *8, 9*
followed by Eli
Whitney, Jr.
Business sold to
Winchester
Repeating Arms
Co. 1888
*3, 4, 5, 6, 7*
#1, 3, 8# #2 7 9#
SPRINGFIELD ARMORY HARPER’S FERRY ARMORY
Capt. John H. Hall
Jas. H. Burton
*15*
#6#
ROBBINS & LAWRENCE SMITH & WESSON
Windsor, Vt. Norwich, Conn. later
Fredk. W. Howe Springfield, Mass.
Henry D. Stone Horace Smith worked
*10 11 12 13 14* for Whitney Arms Co.
D. B. Wesson invented
cartridge, which was
sold to
*16*
#4# #16#
AMES MFG. CO. SAMUEL COLT VOLCANIC ARMS CO.
Chicopee, Mass. Hartford, Conn. Sold to O. F.
N. P. Ames, First revolvers Winchester
Jas. T. Ames, made by Whitney *23 24*
*17* Arms Co.
#15# *19 20 21 22*
Jas. H. Burton
*18*
#12 17# #20# #14 23#
ENFIELD GUN MACHINERY E. K. ROOT TYLER HENRY
and other machinery Built Colt’s Armory: Workman at Robbins &
for European Drop hammers, cartridge Lawrence. Improved the
governments machinery Jennings’ Rifle
*25* *26*
#18 19# #13 21 25# #24 26#
C. M. SPENCER GEO. S. LINCOLN & CO. NEW HAVEN ARMS CO.
Rifles, drop Hartford, Conn. “Henry” Rifle
hammers, automatic Lincoln Miller, first *28*
lathes built for Colt. Pratt
*29* and Whitney were two
of their foremen
*27*
#11# #22 27# #5 28#
JONES & LAMSON MACH. PRATT & WHITNEY WINCHESTER REPEATING
CO. Hartford. Conn. ARMS CO.
Turret lathes, etc. Gun machinery, New Haven, Conn.
machine tools, etc. “Model ’66” Winchester,
etc.
#10 22 29# #30#
BILLINGS & SPENCER HARTFORD MACH. SCR. CO.
Drop Hammers, Drop Forgings, etc. Automatic Lathes, Screw Machine
Billings apprentice at Robbins & Products
Lawrence. Fairfield and Spencer. Both worked
Billings and Spencer worked at at Colt’s
Colt’s.
*30*
FIGURE 27. GENEALOGY OF THE NEW ENGLAND GUN MAKERS]
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.”
[164] Fitch: “Report on Manufactures of Interchangeable Mechanism,”
U. S. Census, 1880. Volume on “Manufactures.”
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 1853 I was appointed a member of the Small Arms Committee for the
purpose of remodeling and, in fact, re-establishing, the Small Arms
Factory at Enfield. The wonderful success of the needle gun in the
war between Prussia and Denmark in 1848 occasioned some alarm amongst
our military authorities as to the state of affairs at home. The
Duke of Wellington to the last proclaimed the sufficiency of “Brown
Bess” as a weapon of offense and defense; but matters could no longer
be deferred. The United States Government, though possessing only a
very small standing army, had established at Springfield a small arms
factory, where, by the use of machine tools specially designed to
execute with the most unerring precision all the details of muskets
and rifles, they were enabled to dispense with mere manual dexterity,
and to produce arms to any amount. It was finally determined to
improve the musketry and rifle systems of the English army. The
Government resolved to _introduce the American system_,[165] by
which arms might be produced much more perfectly, and at a great
diminution of cost. It was under such circumstances that the Small
Arms Committee was appointed.
[165] Italics are ours.
Colonel Colt had brought to England some striking examples of
the admirable tools used at Springfield[166] and he established
a manufactory at Pimlico for the production of his well-known
revolvers. The committee resolved to make a personal visit to the
United States Factory at Springfield. My own business engagements at
home prevented my accompanying the members who were selected; but
as my friend John Anderson (now Sir John) acted as their guide, the
committee had in him the most able and effective helper. He directed
their attention to the most important and available details of that
admirable establishment. The United States Government acted most
liberally in allowing the committee to obtain every information on
the subject; and the heads of the various departments, who were
intelligent and zealous, rendered them every attention and civility.
[166] Hartford?
The members of the mission returned home enthusiastically delighted
with the results of their inquiry. The committee immediately
proceeded with the entire remodeling of the Small Arms Factory
at Enfield. The workshops were equipped with a complete series
of special machine tools, chiefly obtained from the Springfield
factory.[167] The United States Government also permitted several of
their best and most experienced workmen and superintendents to take
service under the English Government.[168]
[167] This must be a mistake. The machinery seems to have been
supplied chiefly by Bobbins & Lawrence and the Ames Mfg. Co. Mr.
Burton of the latter company installed it.
[168] Autobiography of James Nasmyth, pp. 362-363.
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.
[169] For a detailed account of this machine and its history see
_American Machinist_, Vol. XXXVI, p. 1037.
[Illustration: FIGURE 28. THE FIRST MILLING MACHINE
BUILT BY ELI WHITNEY ABOUT 1818. NOW IN THE MASON LABORATORY, YALE
UNIVERSITY]
[Illustration: FIGURE 29. BLANCHARD “GUN-STOCKING” LATHE
BUILT IN 1818 FOR THE SPRINGFIELD ARMORY. IN USE OVER FIFTY YEARS]
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.