Machine tool
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A machine tool is a powered mechanical device, typically used to fabricate metal components of machines by machining, which is the selective removal of metal. The term machine tool is usually reserved for tools that used a power source other than human movement, but they can be powered by people if appropriately set up. Many historians of technology consider that the true machine tools were born when direct human involvement was removed from the shaping or stamping process of the different kinds of tools. The earliest lathe with direct mechanical control of the cutting tool was a screw-cutting lathe dating to about 1483.[1] This lathe "produced screw threads out of wood and employed a true compound slide rest".
The first machine tools offered for sale (i.e. commercially available) were constructed by one Matthew Murray in England around 1800.[2]
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[edit] Overview
Machine tools can be powered from a variety of sources. Human and animal power are options, as is energy captured through the use of waterwheels. However, modern machine tools began to develop only after the development of the steam engine, which led to the Industrial Revolution. Today, most machine tools are powered by electricity.
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 punch cards to control their motion. In the 1960s, computers 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.
From the simplest to the most complex, most machine tools are capable of at least partial self-replication, and produce machine parts as their primary function.
[edit] Examples
Examples of machine tools are:
- Broaching machine
- Drill press
- Gear shaper
- Hobbing machine
- Hone
- Lathe
- Screw machines
- Milling machine
- Shaper
- Saws
- Planer
- Stewart platform mills
- Grinders
When fabricating or shaping parts, several techniques are used to remove unwanted metal. Among these are:
- Electrical discharge machining
- Grinding
- 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.
Several regions of the United States became centers for machine tool development between 1800 and 1950, including Philadelphia, Pennsylvania; Cincinnati, Ohio; Rockford, Illinois; Providence, Rhode Island; Springfield, Vermont; Windsor, Vermont; Hartford, Connecticut; and Bridgeport, Connecticut.
[edit] See also
- Four slide machine
- Tool bit
- Tool wear
- Clanking Replicator
- Multimachine - an open source machine tool
- James Fox (engineer)
- Machinist calculator
- Metalworking
- Swarf
[edit] References
[edit] Bibliography
- Moore, Wayne R. (1970), Foundations of Mechanical Accuracy (1st ed.), Bridgeport, CT, USA: Moore Special Tool Co., LCCN 73-127307.
[edit] Further reading
- Hounshell, David A. (1984), From the American system to mass production, 1800-1932: The development of manufacturing technology in the United States, Baltimore, Maryland, USA: Johns Hopkins University Press, LCCN 83-016269, ISBN 978-0-8018-2975-8.
- Moltrecht, Karl Hans (1981), Machine Shop Practice (2 vols) (2nd ed.), New York: Industrial Press, LCCN 79-091236, ISBN 978-0831111267.
- Noble, David F. (1984), Forces of production: a social history of industrial automation, New York: Knopf, LCCN 83-048867, ISBN 978-0-394-51262-4.
- Roe, Joseph Wickham (1916), English and American Tool Builders, New Haven, Connecticut, USA: Yale University Press, LCCN 16-011753, http://books.google.com/books?id=X-EJAAAAIAAJ&printsec=titlepage. Reprinted by McGraw-Hill, New York and London, 1926 (LCCN 27-024075); and by Lindsay Publications, Inc., Bradley, IL, USA (ISBN 978-0-917914-73-7).
- Rolt, L.T.C. (1965), A Short History of Machine Tools, Cambridge, Massachusetts, USA: MIT Press, LCCN 65-12439. Co-edition published as Rolt, L.T.C. (1965), Tools for the Job: a Short History of Machine Tools, London: B. T. Batsford, LCCN 65-080822.
- Woodbury, Robert S. (1972), Studies in the History of Machine Tools, Cambridge, Massachusetts, USA, and London, England: MIT Press, LCCN 72-006354, ISBN 978-0-262-73033-4. Collection of previously published monographs bound as one volume.
[edit] External links
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Look up machine tool in Wiktionary, the free dictionary. |
- National Institute for Metalworking Skills Standards download page
- U.S. Department of Labor Bureau of Labor Statistics Occupational Outlook Handbook
- American Precision Museum—A museum that preserves historically important machine tools and helps to educate on the history of machine tools
- Canadian Museum of Making
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