Micrometer

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Micrometer
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This article is about the measuring device. For the unit of length, see Micrometre. This article needs additional citations for verification. Please help improve this article by adding citations to reliable sources. Unsourced material may be challenged and removed. (September 2011)

Modern micrometer (value: 1.64 milimeters)

Outside, inside, and depth micrometers
A micrometer (pron.: /maɪˈkrɒmɨtər/ US dict: mī•krŏm′•ĭ•tər), sometimes known as a micrometer screw gauge, is a device incorporating a calibrated screw used widely for precise measurement of small distances in mechanical engineering and machining as well as most mechanical trades, along with other metrological instruments such as dial, vernier, and digital calipers. Micrometers are often, but not always, in the form of calipers. Colloquially the word micrometer is often shortened to mike or mic (/ˈmaɪk/) (US dict: mīk′). Contents

[hide]
1 History of the device and its name
2 Types
o2.1 Basic types
o2.2 Specialized types
3 Operating principles
4 Parts
5 Reading
o5.1 Inch system
o5.2 Metric system
o5.3 Vernier
6 Torque repeatability via torque-limiting ratchets or sleeves •7 Calibration: testing and adjusting
o7.1 Testing
o7.2 Adjustment
8 Zero error
9 See also
10 References
o10.1 Bibliography
11 External links

[edit] History of the device and its name

Gascoigne's Micrometer as drawn by Robert Hooke
The word micrometer is a neoclassical coinage from Greek micros, "small", and metron, "measure". The Merriam-Webster Collegiate Dictionary[1] says that English got it from French and that its first known appearance in English writing was in 1670. Neither the metre nor the micrometre nor the micrometer (device) as we know them today existed at that time. However, humans of that time did have much need for, and interest in, the ability to measure small things, and small differences; the word no doubt was coined in reference to this endeavor, even if it did not refer specifically to its present-day senses. The first ever micrometric screw was invented by William Gascoigne in the 17th century, as an enhancement of the vernier; it was used in a telescope to measure angular distances between stars and the relative sizes of celestial objects. Henry Maudslay built a bench micrometer in the early 19th century that was jocularly nicknamed "the Lord Chancellor" among his staff because it was the final judge on measurement accuracy and precision in the firm's work. The first documented development of handheld micrometer-screw calipers was by Jean Laurent Palmer of Paris in 1848;[2] the device is therefore often called palmer in French, and tornillo de Palmer ("Palmer screw") in Spanish. (Those languages also use the micrometer cognates: micromètre, micrómetro.) The micrometer caliper was introduced to the mass market in anglophone countries by Brown & Sharpe in 1867,[3] allowing the penetration of the instrument's use into the average machine shop. Brown & Sharpe were inspired by several earlier devices, one of them being Palmer's design. In 1888 Edward Williams Morley added to the precision of micrometric measurements and proved their accuracy in a complex series of experiments. The culture of toolroom accuracy and precision, which started with interchangeability pioneers including Gribeauval, Tousard, North, Hall, Whitney, and Colt, and continued through leaders such as Maudslay, Palmer, Whitworth, Brown, Sharpe, Pratt, Whitney, Leland, and others, grew during the Machine Age to become an important part of combining applied science with technology. Beginning in the early 20th century, one could no longer truly master tool and die making, machine tool building, or engineering without some knowledge of the science of metrology, as well as the sciences of chemistry and physics (for metallurgy, kinematics/dynamics, and...
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