When an engineer asks for a material with a specific hardness, it is important that that hardness level is achieved. If he or she demands Rockwell hardness numbers, it is crucial to use a Rockwell hardness tester. Substituting a different test can cause errors in the results, because converting numbers from one tester to another is not the same as converting inches to centimeters. Hardness testing is comparative, unlike other measurements that relate to the object’s physical properties. An understanding of how these tools work and what steps to take to ensure accurate results can be useful for those who need to get it right.
How are Rockwell testers different than Brinell, Vicker, and Knoop testers? All of these hardness testers use indenters to obtain measurements, but they do so in different ways. Brinell, Vicker, and Knoop testers work by pressing an indenter into an object and then measuring the characteristics of the indent. Rockwell testers, on the other hand, measure how deep the indenter goes into an object. This type of test is often more accurate because other testers rely on manual measurements that can fall to subjective errors.
When running a hardness tester, the setup is often more important than people realize to the correctness of the readings. Having a clear indentation is crucial, so any object being tested should have a polished surface. The object needs to be placed in the machine so that it is parallel and perpendicular to the indenter. Using the highest load possible means that the indent will be larger and thus easier to measure.
No one wants to be on a plane where the metal cannot withstand the impact of landing, and no one wants to use a hammer that cannot hit a nail without chipping. Using the right hardness tester correctly ensures people’s safety. If a Rockwell test is asked for, do not use any other tester other than the one specified. Using the wrong one could go so far as to endanger the lives of innocent people.
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