Related Glossary Terms
Checking measuring instruments and devices against a master set to ensure that, over time, they have remained dimensionally stable and nominally accurate.
Hardness is a measure of the resistance of a material to surface indentation or abrasion. There is no absolute scale for hardness. In order to express hardness quantitatively, each type of test has its own scale, which defines hardness. Indentation hardness obtained through static methods is measured by Brinell, Rockwell, Vickers and Knoop tests. Hardness without indentation is measured by a dynamic method, known as the Scleroscope test.
Measure of length that is equal to one-millionth of a meter.
A full line of highly spherical sapphire and ruby balls with precise surface finishes for applications requiring superior hardness and chemical resistance are available from Meller Optics Inc.
Meller Sapphire and Ruby Balls feature Mohs 9 hardness, which is second only to diamond and are impervious to most chemicals, solvents and detergents. Offered in a wide range of sizes, they are suitable for applications such as ball check valves, chromatography pistons and pumps, jewel bearings in time pieces, stylus tips, and fiberoptic and endoscope lens assemblies.
Supplied with a calibration certificate validating diameter and sphericity, Meller sapphire and ruby balls are available in 42 inch and metric sizes from 0.1 mm to 0.5” dia. and have surface finishes of 0.008 to 0.010 micron Ra. They have a 0.2 coefficient-of-friction, a refraction index of 1.76 microns at 20°C, and 2,000°C melting point.