
A machine tool is a
machine
A machine is a physical system that uses power to apply forces and control movement to perform an action. The term is commonly applied to artificial devices, such as those employing engines or motors, but also to natural biological macromol ...
for handling or
machining
Machining is a manufacturing process where a desired shape or part is created using the controlled removal of material, most often metal, from a larger piece of raw material by cutting. Machining is a form of subtractive manufacturing, which util ...
metal or other rigid materials, usually by cutting,
boring,
grinding, shearing, or other forms of deformations. Machine tools employ some sort of tool that does the cutting or shaping. All machine tools have some means of constraining the
workpiece and provide a guided movement of the parts of the machine. Thus, the relative movement between the workpiece and the
cutting tool
Cutting is the separation or opening of a physical object, into two or more portions, through the application of an acutely directed force.
Implements commonly used for cutting are the knife and saw, or in medicine and science the scalpel an ...
(which is called the toolpath) is controlled or constrained by the machine to at least some extent, rather than being entirely "offhand" or "
freehand". It is a power-driven metal cutting machine which assists in managing the needed relative motion between cutting tool and the job that changes the size and shape of the job material.
The precise definition of the term ''machine tool'' varies among users. While all machine tools are "machines that help people to make things", not all factory machines are machine tools.
Today machine tools are typically powered other than by the human muscle (e.g., electrically, hydraulically, or via
line shaft), used to make manufactured parts (components) in various ways that include cutting or certain other kinds of deformation.
With their inherent precision, machine tools enabled the economical production of
interchangeable parts
Interchangeable parts are parts (wikt:component#Noun, components) that are identical for practical purposes. They are made to specifications that ensure that they are so nearly identical that they will fit into any assembly of the same type. One ...
.
Nomenclature and key concepts, interrelated
Many
historians of technology consider that true machine tools were born when the toolpath first became guided by the machine itself in some way, at least to some extent, so that direct,
freehand human guidance of the toolpath (with hands, feet, or mouth) was no longer the only guidance used in the cutting or forming process. In this view of the definition, the term, arising at a time when all tools up till then had been
hand tools, simply provided a label for "tools that were machines instead of hand tools". Early
lathes, those prior to the late
medieval
In the history of Europe, the Middle Ages or medieval period lasted approximately from the 5th to the late 15th centuries, similarly to the post-classical period of World history (field), global history. It began with the fall of the West ...
period, and modern woodworking lathes and
potter's wheels may or may not fall under this definition, depending on how one views the headstock
spindle itself; but the earliest historical records of a lathe with direct mechanical control ''of the cutting tool's path'' are of a screw-cutting lathe dating to about 1483.
[.] This lathe "produced screw threads out of wood and employed a true compound slide rest".
[
In the 1930s, the U.S. National Bureau of Economic Research (NBER) referenced the definition of a machine tool as "any machine operating by other than hand power which employs a tool to work on metal".][.]
The narrowest colloquial sense of the term reserves it only for machines that perform metal cutting—in other words, the many kinds of conventional machining
Machining is a manufacturing process where a desired shape or part is created using the controlled removal of material, most often metal, from a larger piece of raw material by cutting. Machining is a form of subtractive manufacturing, which util ...
and grinding. These processes are a type of deformation that produces swarf. However, economist
An economist is a professional and practitioner in the social sciences, social science discipline of economics.
The individual may also study, develop, and apply theories and concepts from economics and write about economic policy. Within this ...
s use a slightly broader sense that also includes metal deformation of other types that squeeze the metal into shape without cutting off swarf, such as rolling, stamping with dies, shearing, swaging, riveting, and others. Thus presses are usually included in the economic definition of machine tools. For example, this is the breadth of definition used by Max Holland in his history of Burgmaster and Houdaille,[.] which is also a history of the machine tool industry in general from the 1940s through the 1980s; he was reflecting the sense of the term used by Houdaille itself and other firms in the industry. Many reports on machine tool export
An export in international trade is a good produced in one country that is sold into another country or a service provided in one country for a national or resident of another country. The seller of such goods or the service provider is a ...
and import and similar economic topics use this broader definition.
The colloquial sense implying conventional metal cutting is also growing obsolete because of changing technology over the decades. The many more recently developed processes labeled "machining", such as electrical discharge machining, electrochemical machining, electron beam machining, photochemical machining, and ultrasonic machining, or even plasma cutting and water jet cutting, are often performed by machines that could most logically be called machine tools. In addition, some of the newly developed additive manufacturing processes, which are not about cutting away material but rather about adding it, are done by machines that are likely to end up labeled, in some cases, as machine tools. In fact, machine tool builders are already developing machines that include both subtractive and additive manufacturing in one work envelope, and retrofits of existing machines are underway.
History
Forerunners of machine tools included bow drill
A bow drill is a simple hand-operated type of tool, consisting of a rod (the ''spindle'' or ''drill shaft'') that is set in rapid rotary motion by means of a cord wrapped around it, kept taut by a bow and arrow, bow which is pushed back and forth ...
s and potter's wheels, which had existed in ancient Egypt
Ancient Egypt () was a cradle of civilization concentrated along the lower reaches of the Nile River in Northeast Africa. It emerged from prehistoric Egypt around 3150BC (according to conventional Egyptian chronology), when Upper and Lower E ...
prior to 2500 BC, and lathes, known to have existed in multiple regions of Europe since at least 1000 to 500 BC.[.] But it was not until the later Middle Ages
In the history of Europe, the Middle Ages or medieval period lasted approximately from the 5th to the late 15th centuries, similarly to the post-classical period of global history. It began with the fall of the Western Roman Empire and ...
and the Age of Enlightenment
The Age of Enlightenment (also the Age of Reason and the Enlightenment) was a Europe, European Intellect, intellectual and Philosophy, philosophical movement active from the late 17th to early 19th century. Chiefly valuing knowledge gained th ...
that the modern concept of a machine tool—a class of machines used as tools in the making of metal parts, and incorporating machine-guided toolpath—began to evolve. Clockmakers of the Middle Ages and renaissance men such as Leonardo da Vinci
Leonardo di ser Piero da Vinci (15 April 1452 - 2 May 1519) was an Italian polymath of the High Renaissance who was active as a painter, draughtsman, engineer, scientist, theorist, sculptor, and architect. While his fame initially rested o ...
helped expand humans' technological milieu toward the preconditions for industrial machine tools. During the 18th and 19th centuries, and even in many cases in the 20th, the builders of machine tools tended to be the same people who would then use them to produce the end products (manufactured goods). However, from these roots also evolved an industry of machine tool builders as we define them today, meaning people who specialize in building machine tools for sale to others.
Historians of machine tools often focus on a handful of major industries that most spurred machine tool development. In order of historical emergence, they have been firearm
A firearm is any type of gun that uses an explosive charge and is designed to be readily carried and operated by an individual. The term is legally defined further in different countries (see legal definitions).
The first firearms originate ...
s (small arms and artillery
Artillery consists of ranged weapons that launch Ammunition, munitions far beyond the range and power of infantry firearms. Early artillery development focused on the ability to breach defensive walls and fortifications during sieges, and l ...
); clocks; textile machinery; steam engines ( stationary, marine, rail, and otherwise) (the story of how Watt
The watt (symbol: W) is the unit of Power (physics), power or radiant flux in the International System of Units (SI), equal to 1 joule per second or 1 kg⋅m2⋅s−3. It is used to quantification (science), quantify the rate of Work ...
's need for an accurate cylinder spurred Boulton's boring machine is discussed by Roe); sewing machines; bicycle
A bicycle, also called a pedal cycle, bike, push-bike or cycle, is a human-powered transport, human-powered or motorized bicycle, motor-assisted, bicycle pedal, pedal-driven, single-track vehicle, with two bicycle wheel, wheels attached to a ...
s; automobile
A car, or an automobile, is a motor vehicle with wheels. Most definitions of cars state that they run primarily on roads, Car seat, seat one to eight people, have four wheels, and mainly transport private transport#Personal transport, peopl ...
s; and aircraft
An aircraft ( aircraft) is a vehicle that is able to flight, fly by gaining support from the Atmosphere of Earth, air. It counters the force of gravity by using either Buoyancy, static lift or the Lift (force), dynamic lift of an airfoil, or, i ...
. Others could be included in this list as well, but they tend to be connected with the root causes already listed. For example, rolling-element bearings are an industry of themselves, but this industry's main drivers of development were the vehicles already listed—trains, bicycles, automobiles, and aircraft; and other industries, such as tractors, farm implements, and tanks, borrowed heavily from those same parent industries.
Machine tools filled a need created by textile machinery during the Industrial Revolution
The Industrial Revolution, sometimes divided into the First Industrial Revolution and Second Industrial Revolution, was a transitional period of the global economy toward more widespread, efficient and stable manufacturing processes, succee ...
in England in the middle to late 1700s.[ Until that time, machinery was made mostly from wood, often including gearing and shafts. The increase in ]mechanization
Mechanization (or mechanisation) is the process of changing from working largely or exclusively by hand or with animals to doing that work with machinery. In an early engineering text, a machine is defined as follows:
In every fields, mechan ...
required more metal parts, which were usually made of cast iron
Cast iron is a class of iron–carbon alloys with a carbon content of more than 2% and silicon content around 1–3%. Its usefulness derives from its relatively low melting temperature. The alloying elements determine the form in which its car ...
or wrought iron. Cast iron could be cast in molds for larger parts, such as engine cylinders and gears, but was difficult to work with a file and could not be hammered. Red hot wrought iron could be hammered into shapes. Room temperature wrought iron was worked with a file and chisel and could be made into gears and other complex parts; however, hand working lacked precision and was a slow and expensive process.
James Watt was unable to have an accurately bored cylinder for his first steam engine, trying for several years until John Wilkinson invented a suitable boring machine in 1774, boring Boulton & Watt's first commercial engine in 1776.[
The advance in the accuracy of machine tools can be traced to Henry Maudslay and refined by Joseph Whitworth. That Maudslay had established the manufacture and use of master plane gages in his shop (Maudslay & Field) located on Westminster Road south of the Thames River in London about 1809, was attested to by James Nasmyth who was employed by Maudslay in 1829 and Nasmyth documented their use in his autobiography.
The process by which the master plane gages were produced dates back to antiquity but was refined to an unprecedented degree in the Maudslay shop. The process begins with three square plates each given an identification (ex., 1,2 and 3). The first step is to rub plates 1 and 2 together with a marking medium (called bluing today) revealing the high spots which would be removed by hand scraping with a steel scraper, until no irregularities were visible. This would not produce true plane surfaces but a "ball and socket" concave-concave and convex-convex fit, as this mechanical fit, like two perfect planes, can slide over each other and reveal no high spots. The rubbing and marking are repeated after rotating 2 relative to 1 by 90 degrees to eliminate concave-convex "potato-chip" curvature. Next, plate number 3 is compared and scraped to conform to plate number 1 in the same two trials. In this manner plates number 2 and 3 would be identical. Next plates number 2 and 3 would be checked against each other to determine what condition existed, either both plates were "balls" or "sockets" or "chips" or a combination. These would then be scraped until no high spots existed and then compared to plate number 1. Repeating this process of comparing and scraping the three plates could produce plane surfaces accurate to within millionths of an inch (the thickness of the marking medium).
The traditional method of producing the surface gages used an abrasive powder rubbed between the plates to remove the high spots, but it was Whitworth who contributed the refinement of replacing the grinding with hand scraping. Sometime after 1825, Whitworth went to work for Maudslay and it was there that Whitworth perfected the hand scraping of master surface plane gages. In his paper presented to the British Association for the Advancement of Science at Glasgow in 1840, Whitworth pointed out the inherent inaccuracy of grinding due to no control and thus unequal distribution of the abrasive material between the plates which would produce uneven removal of material from the plates.
With the creation of master plane gages of such high accuracy, all critical components of machine tools (i.e., guiding surfaces such as machine ways) could then be compared against them and scraped to the desired accuracy.][
The first machine tools offered for sale (i.e., commercially available) were constructed by Matthew Murray in England around 1800.][.] Others, such as Henry Maudslay, James Nasmyth, and Joseph Whitworth, soon followed the path of expanding their entrepreneurship from manufactured end products and millwright work into the realm of building machine tools for sale.
Important early machine tools included the slide rest lathe, screw-cutting lathe, turret lathe, milling machine, pattern tracing lathe, shaper, and metal planer, which were all in use before 1840. With these machine tools the decades-old objective of producing interchangeable parts
Interchangeable parts are parts (wikt:component#Noun, components) that are identical for practical purposes. They are made to specifications that ensure that they are so nearly identical that they will fit into any assembly of the same type. One ...
was finally realized. An important early example of something now taken for granted was the standardization of screw fasteners such as nuts and bolts. Before about the beginning of the 19th century, these were used in pairs, and even screws of the same machine were generally not interchangeable. Methods were developed to cut screw thread to a greater precision than that of the feed screw in the lathe being used. This led to the bar length standards of the 19th and early 20th centuries.
American production of machine tools was a critical factor in the Allies' victory in World War II. Production of machine tools tripled in the United States in the war. No war was more industrialized than World War II, and it has been written that the war was won as much by machine shops as by machine guns.
The production of machine tools is concentrated in about 10 countries worldwide: China, Japan, Germany, Italy, South Korea, Taiwan, Switzerland, US, Austria, Spain and a few others. Machine tool innovation continues in several public and private research centers worldwide.
Drive power sources
Machine tools can be powered from a variety of sources. Human and animal power (via cranks, treadles, treadmills, or treadwheels) were used in the past, as was water power (via water wheel
A water wheel is a machine for converting the kinetic energy of flowing or falling water into useful forms of power, often in a watermill. A water wheel consists of a large wheel (usually constructed from wood or metal), with numerous b ...
); however, following the development of high-pressure steam engines in the mid 19th century, factories increasingly used steam power. Factories also used hydraulic and pneumatic power. Many small workshops continued to use water, human and animal power until electrification
Electrification is the process of powering by electricity and, in many contexts, the introduction of such power by changing over from an earlier power source. In the context of history of technology and economic development, electrification refe ...
after 1900.[
]
Today most machine tools are powered by electricity; hydraulic and pneumatic power are sometimes used, but this is uncommon.
Automatic control
Machine tools can be operated manually, or under automatic control. Early machines used flywheels to stabilize their motion and had complex systems of gears and levers to control the machine and the piece being worked on. Soon after World War II, the numerical control (NC) machine was developed. NC machines used a series of numbers punched on paper tape or punched card
A punched card (also punch card or punched-card) is a stiff paper-based medium used to store digital information via the presence or absence of holes in predefined positions. Developed over the 18th to 20th centuries, punched cards were widel ...
s to control their motion. In the 1960s, computers
A computer is a machine that can be programmed to automatically carry out sequences of arithmetic or logical operations ('' computation''). Modern digital electronic computers can perform generic sets of operations known as ''programs'', ...
were added to give even more flexibility to the process. Such machines became known as computerized numerical control (CNC) machines. NC and CNC machines could precisely repeat sequences over and over, and could produce much more complex pieces than even the most skilled tool operators.
Before long, the machines could automatically change the specific cutting and shaping tools that were being used. For example, a drill machine might contain a magazine with a variety of drill bits for producing holes of various sizes. Previously, either machine operators would usually have to manually change the bit or move the work piece to another station to perform these different operations. The next logical step was to combine several different machine tools together, all under computer control. These are known as machining centers, and have dramatically changed the way parts are made.
Examples
Examples of machine tools are:
* Broaching machine
* Drill press
* Gear shaper
* Hobbing machine
* Hone
* Lathe
* Honing Machine
* Screw machines
* Milling machine
* Shear (sheet metal)
* Shaper
* Bandsaw
Saws
* Planer
* Stewart platform
A Stewart platform is a type of parallel manipulator that has six prismatic joint, prismatic actuators, commonly hydraulic jacks or electric linear actuators, attached in pairs to three positions on the platform's baseplate, crossing over to thr ...
mills
* Grinding machines
* Multitasking machines (MTMs)—CNC machine tools with many axes that combine turning, milling, grinding, and material handling into one highly automated machine tool
When fabricating or shaping parts, several techniques are used to remove unwanted metal. Among these are:
* Electrical discharge machining
* Grinding (abrasive cutting)
* Multiple edge cutting tools
* Single edge cutting tools
Other techniques are used to ''add'' desired material. Devices that fabricate components by selective ''addition'' of material are called rapid prototyping machines.
Machine tool manufacturing industry
The worldwide market for machine tools was approximately $81 billion in production in 2014 according to a survey by market research firm Gardner Research. The largest producer of machine tools was China with $23.8 billion of production followed by Germany and Japan at neck and neck with $12.9 billion and $12.88 billion respectively.[ South Korea and Italy rounded out the top 5 producers with revenue of $5.6 billion and $5 billion respectively.][
]
See also
References
Bibliography
* ''A history most specifically of Burgmaster, which specialized in turret drills; but in telling Burgmaster's story, and that of its acquirer Houdaille, Holland provides a history of the machine tool industry in general between World War II and the 1980s that ranks with Noble's coverage of the same era (Noble 1984) as a seminal history. Later republished under the title ''From Industry to Alchemy: Burgmaster, a Machine Tool Company''. ''
*
* . ''The Moore family firm, the Moore Special Tool Company, independently invented the jig borer (contemporaneously with its Swiss invention), and Moore's monograph is a seminal classic of the principles of machine tool design and construction that yield the highest possible accuracy and precision
Accuracy and precision are two measures of ''observational error''.
''Accuracy'' is how close a given set of measurements (observations or readings) are to their ''true value''.
''Precision'' is how close the measurements are to each other.
The ...
in machine tools (second only to that of metrological machines). The Moore firm epitomized the art and science of the tool and die maker.''
* . ''A seminal classic of machine tool history. Extensively cited by later works.''
*
*
* . Collection of previously published monographs bound as one volume. A collection of seminal classics of machine tool history.
Further reading
* ''A memoir that contains quite a bit of general history of the industry.''
* . ''A monograph with a focus on history, economics, and import and export policy. Original 1976 publication: LCCN 75-046133, .''
* ''One of the most detailed histories of the machine tool industry from the late 18th century through 1932. Not comprehensive in terms of firm names and sales statistics (like Floud focuses on), but extremely detailed in exploring the development and spread of practicable interchangeability, and the thinking behind the intermediate steps. Extensively cited by later works.''
* ''One of the most detailed histories of the machine tool industry from World War II through the early 1980s, relayed in the context of the social impact of evolving automation via NC and CNC.''
* . ''A biography of a machine tool builder that also contains some general history of the industry.''
*
* Ryder, Thomas and Son, ''Machines to Make Machines 1865 to 1968'', a centenary booklet, (Derby: Bemrose & Sons, 1968)
External links
Milestones in the History of Machine Tools
{{Authority control
Industrial machinery
Machines
Machining
Tools
Woodworking