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The eBearing Glossary of Bearing Industry Terms
Definitions and Illustrations
M
Magnetic Bearing
A non-contact bearing which operates by maintaining a magnetic field between
two surfaces.
The magnetic force must be sufficiently strong to maintain an operating gap
between the two surfaces. In addition, the relative locations of the two
surfaces must often be controlled and stabilized by mechanical means.
Martensite
Named for Adolf Martens (1850-1914), director of Berlin's Royal Mechanical Laboratory.
The generic term for microstructures formed by the diffusionless phase transformation
in which the parent and product phases have a specific crystallographic relationship.
Martensite is characterized by an acicular pattern in the microstructure of ferrous and nonferrous
alloys. In alloys where the solute atoms occupy interstitial positions in the martensitic
lattice, the martensite is hard and highly strained. Where the solute
atoms occupy substitutional positions, the martensite is soft and
ductile. The amount of high-temperature phase that transforms into martensite upon cooling depends
upon the lowest temperature reached. Martensite has a distinct starting temperature (Ms) and
a temperature at which the transformation is finished (Mf).
McCoy, Elijah (1843-1929)
Canadian-born inventor and entrepreneur, often improperly credited with the invention
of hydrostatic and/or hydrodynamic bearing lubricators, and/or their adaptation to
superheated steam engine applications.
There is often a second part to this pervasive urban legend, crediting demand for Mr. McCoy's bearing
lubricators as the source of the colloquialism, wanting "the real McCoy." However, no engineer would ever
demand a McCoy lubricator over another design; it was either the proper application or not. Instead,
tribologists
know bearing lubricators predate Mr. McCoy by many centuries, and linguists have tracked the phrase
to an early 1900's McKay Scotch whiskey advertising slogan, suggesting people to ask for, "the real McKay."
Microtribology
A sub-specialization of tribology, the study of friction, wear and
lubrication involved or required
when two moving surfaces are in contact.
Mohs Hardness Scale
Hardness measured on the Mohs scale is identified by the numeric hardness
assigned to basic minerals from 1 (softest) to 10 (hardest).
1. Talc
2. Gypsum
3. Clacite
4. Fluorite
5. Apatite
6. Orthoclase
7. Quartz
8. Topaz
9. Corundum
10. Diamond
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