03 August 2009

Interchangeable parts

The invention: 

A key idea in the late Industrial Revolution, the
interchangeability of parts made possible mass production of
identical products.

The people behind the invention:

Henry M. Leland (1843-1932), president of Cadillac Motor Car
Company in 1908, known as a master of precision
Frederick Bennett, the British agent for Cadillac Motor Car
Company who convinced the Royal Automobile Club to run
the standardization test at Brooklands, England
Henry Ford (1863-1947), founder of Ford Motor Company who
introduced the moving assembly line into the automobile
industry in 1913

An American Idea

Mass production is a twentieth century methodology that for the
most part is a result of nineteenth century ideas. It is a phenomenon
that, although its origins were mostly American, has consequently
changed the entire world. The use of interchangeable parts, the feasibility
of which was demonstrated by the Cadillac Motor Car Company
in 1908, was instrumental in making mass production possible.
The British phase of the Industrial Revolution saw the application
of division of labor, the first principle of industrialization, to capitalist directed
manufacturing processes. Centralized power sources were
connected through shafts, pulleys, and belts to machines housed in
factories. Even after these dramatic changes, the British preferred to
produce unique, handcrafted products formed one step at a time using
general-purpose machine tools. Seldom did they make separate components
to be assembled into standardized products.
Stories about American products that were assembled from fully
interchangeable parts began to reach Great Britain. In 1851, the British
public saw a few of these products on display at an exhibition in
London’s Crystal Palace. In 1854, they were informed by one of their
own investigative commissions that American manufacturers were
Stories about American products that were assembled from fully
interchangeable parts began to reach Great Britain. In 1851, the British
public saw a few of these products on display at an exhibition in
London’s Crystal Palace. In 1854, they were informed by one of their
own investigative commissions that American manufacturers were
building military weapons and a number of consumer products
with separately made parts that could be easily assembled, with little
filing and fitting, by semiskilled workers.
English industrialists had probably heard as much as they ever
wanted to about this so-called “American system of manufacturing”
by the first decade of the twentieth century, when word came
that American companies were building automobiles with parts
manufactured so precisely that they were interchangeable.

The Cadillac

During the fall of 1907, Frederick Bennett, an Englishman who
served as the British agent for the Cadillac Motor Car Company, paid
a visit to the company’s Detroit, Michigan, factory and was amazed
at what he saw. He later described the assembling of the relatively inexpensive
Cadillac vehicles as a demonstration of the beauty and
practicality of precision. He was convinced that if his countrymen
could see what he had seen they would also be impressed.
Most automobile builders at the time claimed that their vehicles
were built with handcrafted quality, yet at the same time they advertised
that they could supply repair parts that would fit perfectly.
In actuality, machining and filing were almost always required
when parts were replaced, and only shops with proper equipment
could do the job.
Upon his return to London, Bennett convinced the Royal Automobile
Club to sponsor a test of the precision of automobile parts. A
standardization test was set to begin on February 29, 1908, and all of
the companies then selling automobiles were invited to participate.
Only the company that Bennett represented, Cadillac, was willing
to enter the contest.
Three one-cylinder Cadillacs, each painted a different color, were
taken from stock at the company’s warehouse in London to a garage
near the Brooklands race track. The cars were first driven around
the track ten times to prove that they were operable. British mechanics
then dismantled the vehicles, placing their parts in piles in the
center of the garage, making sure that there was no way of identifying
from which car each internal piece came. Then, as a further test,
eighty-nine randomly selected parts were removed from the piles
and replaced with new ones straight from Cadillac’s storeroom in
London. The mechanics then proceeded to reassemble the automobiles,
using only screwdrivers and wrenches.
After the reconstruction, which took two weeks, the cars were
driven from the garage. They were a motley looking trio, with fenders,
doors, hoods, and wheels of mixed colors. All three were then
driven five hundred miles around the Brooklands track. The British
were amazed. Cadillac was awarded the club’s prestigious Dewar
Trophy, considered in the young automobile industry to be almost
the equivalent of a Nobel Prize. A number of European and American
automobile manufacturers began to consider the promise of interchangeable
parts and the assembly line system.

Henry M. Leland

Cadillac’s precision-built automobiles were the result of a lifetime
of experience of Henry M. Leland, an American engineer.
Known in Detroit at the turn of the century as a master of precision,
Leland became the primary connection between a series of nineteenth
century attempts to make interchangeable parts and the
large-scale use of precision parts in mass production manufacturing
during the twentieth century.
The first American use of truly interchangeable parts had occurred
in the military, nearly three-quarters of a century before the
test at Brooklands. Thomas Jefferson had written from France about
a demonstration of uniform parts for musket locks in 1785. A few
years later, Eli Whitney attempted to make muskets for the American
military by producing separate parts for assembly using specialized
machines. He was never able to produce the precision necessary
for truly interchangeable parts, but he promoted the idea
intensely. It was in 1822 at the Harpers Ferry Armory in Virginia,
and then a few years later at the Springfield Armory in Massachusetts,
that the necessary accuracy in machining was finally achieved
on a relatively large scale.
Leland began his career at the Springfield Armory in 1863, at the
age of nineteen. He worked as a tool builder during the Civil War
years and soon became an advocate of precision manufacturing. In
1890, Leland moved to Detroit, where he began a firm, Leland &
Faulconer, that would become internationally known for precision
machining. His company did well supplying parts to the bicycle industry
and internal combustion engines and transmissions to early
automobile makers. In 1899, Leland & Faulconer became the primary
supplier of engines to the first of the major automobile producers,
the Olds Motor Works.
In 1902, the directors of another Detroit firm, the Henry Ford
Company, found themselves in a desperate situation. Henry Ford,
the company founder and chief engineer, had resigned after a disagreement
with the firm’s key owner,William Murphy. Leland was
asked to take over the reorganization of the company. Because it
could no longer use Ford’s name, the business was renamed in
memory of the French explorer who had founded Detroit two hundred
years earlier, Antoine de la Mothe Cadillac.
Leland was appointed president of the Cadillac Motor Car Company.
The company, under his influence, soon became known for its
precision manufacturing. He disciplined its suppliers, rejecting anything
that did not meet his specifications, and insisted on precision
machining for all parts. By 1906, Cadillac was outselling all of its
competitors, including Oldsmobile and Ford’s new venture, the
Ford Motor Company. After the Brooklands demonstration in 1908,
Cadillac became recognized worldwide for quality and interchangeability
at a reasonable price.


The Brooklands demonstration went a long way in proving that
mass-produced goods could be durable and of relatively high quality.
It showed that standardized products, although often less costly
to make, were not necessarily cheap substitutes for handcrafted and
painstakingly fitted products. It also demonstrated that, through
the use of interchangeable parts, the job of repairing such complex
machines as automobiles could be made comparatively simple,
moving maintenance and repair work from the well-equipped machine
shop to the neighborhood garage or even to the home.
Because of the international publicity Cadillac received, Leland’s
methods began to be emulated by others in the automobile industry.
His precision manufacturing, as his daughter-in-law would later
write in his biography, “laid the foundation for the future American
[automobile] industry.” The successes of automobile manufacturers
quickly led to the introduction of mass production methods, and
strategies designed to promote their necessary corollary mass consumption,
in many other American businesses.
In 1909, Cadillac was acquired by William Crapo Durant as the
flagship company of his new holding company, which he labeled
General Motors. Leland continued to improve his production methods,
while also influencing his colleagues in the other General Motors
companies to implement many of his techniques. By the mid-
1920’s, General Motors had become the world’s largest manufacturer
of automobiles. Much of its success resulted from extensions
of Leland’s ideas. The company began offering a number of brand
name vehicles in a variety of price ranges for marketing purposes,
while still keeping the costs of production down by including in
each design a large number of commonly used, highly standardized
Henry Leland resigned from Cadillac during World War I after
trying to convince Durant that General Motors should play an important
part in the war effort by contracting to build Liberty aircraft
engines for the military. He formed his own firm, named after his favorite
president, Abraham Lincoln, and went on to build about four
thousand aircraft engines in 1917 and 1918. In 1919, ready to make
automobiles again, Leland converted the Lincoln Motor Company
into a car manufacturer. Again he influenced the industry by setting
high standards for precision, but in 1921 an economic recession
forced his new venture into receivership. Ironically, Lincoln was
purchased at auction by Henry Ford. Leland retired, his name overshadowed
by those of individuals to whom he had taught the importance
of precision and interchangeable parts. Ford, as one example,
went on to become one of America’s industrial legends by
applying the standardized parts concept.

Ford and the Assembly Line

In 1913, Henry Ford, relying on the ease of fit made possible
through the use of machined and stamped interchangeable parts,
introduced the moving assembly line to the automobile industry.
He had begun production of the Model T in 1908 using stationary
assembly methods, bringing parts to assemblers. After having learned
how to increase component production significantly, through experi-
ments with interchangeable parts and moving assembly methods in
the magneto department, he began to apply this same concept to final
assembly. In the spring of 1913, Ford workers began dragging car
frames past stockpiles of parts for assembly. Soon a power source
was attached to the cars through a chain drive, and the vehicles
were pulled past the stockpiles at a constant rate.
From this time on, the pace of tasks performed by assemblers
would be controlled by the rhythm of the moving line. As demand
for the Model T increased, the number of employees along the line
was increased and the jobs were broken into smaller and simpler
tasks. With stationary assembly methods, the time required to assemble
a Model T had averaged twelve and one-half person-hours.
Dragging the chassis to the parts cut the time to six hours per vehicle,
and the power-driven, constant-rate line produced a Model T
with only ninety-three minutes of labor time. Because of these
amazing increases in productivity, Ford was able to lower the selling
price of the basic model from $900 in 1910 to $260 in 1925. He
had revolutionized automobile manufacturing: The average family
could now afford an automobile.
Soon the average family would also be able to afford many of the
other new products they had seen in magazines and newspapers.
At the turn of the century, there were many new household appliances,
farm machines, ready-made fashions, and prepackaged food
products on the market, but only the wealthier class could afford
most of these items. Major consumer goods retailers such as Sears,
Roebuck and Company, Montgomery Ward, and the Great Atlantic
and Pacific Tea Company were anxious to find lower-priced versions
of these products to sell to a growing middle-class constituency.
The methods of mass production that Henry Ford had popularized
seemed to carry promise for these products as well. During
the 1920’s, by working with such key manufacturers as Whirlpool,
Hoover, General Electric, and Westinghouse, these large distributors
helped introduce mass production methods into a large number
of consumer product industries. They changed class markets
into mass markets.
The movement toward precision also led to the birth of a separate
industry based on the manufacture of machine tools. A general
purpose lathe, milling machine, or grinder could be used for a num-
ber of operations, but mass production industries called for narrow purpose
machines designed for high-speed use in performing one
specialized step in the production process. Many more machines
were now required, one at each step in the production process. Each
machine had to be simpler to operate, with more automatic features,
because of an increased dependence on unskilled workers. The machine
tool industry became the foundation of modern production.
The miracle of mass production that followed, in products as
diverse as airplanes, communication systems, and hamburgers,
would not have been possible without the precision insisted upon
by Henry Leland in the first decade of the twentieth century. It
would not have come about without the lessons learned by Henry
Ford in the use of specialized machines and assembly methods, and
it would not have occurred without the growth of the machine tool
industry. Cadillac’s demonstration at Brooklands in 1908 proved
the practicality of precision manufacturing and interchangeable
parts to the world. It inspired American manufacturers to continue
to develop these ideas; it convinced Europeans that such production
was possible; and, for better or for worse, it played a major part
in changing the world.

Henry Martyn Leland

Henry Martyn Leland (1843-1932) is the unsung giant of
early automobile manufacturers, launching two of the bestknown
American car companies, Cadillac and Lincoln, and influenced
the success of General Motors, as well as introducing
the use of interchangeable parts. Had he allowed a model to be
named after him, as did Henry Ford and Ransom Olds, he
might have become a household name too, but he refused any
such suggestion.
Leland worked in factories during his youth. During the
CivilWar he honed his skills as a machinist at the U.S. Armory
in Springfield, Massachusetts, helping build rifles with interchangeable
parts. After the war, he learned how to machine
parts to within one-thousandth of an inch, fabricated the first
mechanical barber’s clippers, and refined the workings of air
brakes for locomotives.
This was all warm-up. In 1890 he moved to Detroit and
opened his own business, Leland and Faulconer Manufacturing
Company, specializing in automobile engines. The 10.25-horsepower
engine he built for Olds in 1901 was rejected, but the single-
cylinder (“one-lunger”) design that powered the first Cadillacs
set him on the high road in the automotive industry. More
innovations followed. He developed the electric starter, electric
lights, and dimmable headlights. During World War I he built
airplane engines for the U.S. government, and afterward converted
the design for use in his new creation, the Lincoln.
Throughout, he demanded precision from himself and those
working for him. Once, for example, he complained to Alfred P.
Sloan that a lot of ball bearings that Sloan had sold him varied
from the required engineering tolerances and showed Sloan a
few misshapen bearings to prove the claim. “Even though you
make thousands,” Leland admonished Sloan, “the first and last
should be precisely the same.” Sloan took the lesson very seriously.
When he later led General Motors to the top of the industry,
he credited Leland with teaching him what mass production
was all about.

See also: CAD/CAM ; Assembly line ; Internal combustion engine .