Diamonds are the hardest substance on the Mohs hardness scale with a rating of 10.
The scientific standard for testing material hardness is called the Mohs hardness scale. The Mohs scale is a comparative scale based on the hardness of minerals. In order to calibrate a hardness scale, the scale needs to be tested and adjusted against the standards of the Mohs scale materials or an equivalent test kit stand-in.
The Mohs Hardness Calibration Standard
The Mohs scale determines hardness based on the hardness of various minerals. The hardest mineral on the Mohs scale is diamond, with a rating of 10, and the softest is talc, with a rating of one. To calibrate a hardness tester, take a reading on a material with a known hardness, such as quartz, which rates a seven. If the reading is out of sync with the known hardness of the material, adjust the device following the methods outlined in the user manual. The Mohs hardness standard scale is sometimes considered unwieldy due to the inherent inconvenience of storing material samples for relative hardness testing during calibration. It is this inconvenience that led to the invention of hardness calibration block kits and fully automated precision devices that require calibration at intervals of a year or more.
Hardness Calibration Testing Block Kits
A material hardness calibration block kit uses a variety of materials ranging in hardness from graphite blocks to steel bars to form a basis for physical hardness testing, which can also be used in a more convenient way than direct comparison to the Mohs hardness mineral examples. Block kits are used in conjunction with specialized micrometers in order to take accurate pressure indent readings. The block kits are ideal both for testing the hardness of a material when compared to the plate and as a more portable alternative to the minerals in the standard Mohs scale.
Precision Automatic Hardness Testers
Automatic hardness testers are factory calibrated, though they typically have a recalibration protocol in place to ensure the long-term accuracy of the device. Common locations where calibration errors occur on an automatic tester are pivot points, knife edges, dead weights and other simple design characteristics. High-quality precision testers reduce or eliminate the number of components that require frequent user recalibration.
Tags: Mohs scale, Mohs hardness, hardness scale, with rating, based hardness
