The Rockwell hardness tester measures a material's hardness by pressing an indenter, either a diamond cone or a hardened steel ball depending on the material and scale, into the surface under a small preliminary load followed by a larger main load, and reading the hardness directly from the difference in indentation depth between the two loads. The American metallurgists Stanley P. Rockwell and Hugh M. Rockwell developed the test while working at a ball bearing manufacturer and were granted a patent for it in 1919, seeking a faster method than the existing Brinell test for checking the hardness of hardened steel bearing races on a production line. Because the Rockwell method reads hardness directly from indentation depth rather than requiring a separate microscope measurement of an indentation's diameter, it became the fastest widely used hardness test and remains standard in production quality control.
Facts
Patent or First-Use Date FAQs
What does a Rockwell hardness tester actually measure?
It compares how deep the indenter goes under a large load against a small preload.
It measures depth. The tester first applies a small preload, called the minor load, and then a large major load. The hardness reading comes from how much deeper the indenter penetrates under the major load than it did under the preload. Different scales, each marked by a single letter, use different loads or indenters.
Connections
Sources
1. Rockwell hardness test, Wikipedia
History section, patent paragraph
The application was approved on February 11, 1919, for U.S. patent 1,294,171.
History
They applied for a patent on July 15, 1914.
In Group: Materials Testing Instruments, Article body
The Rockwell hardness test is a hardness test based on indentation hardness of a material.
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