What is the Rockwell Hardness Test?

The Rockwell hardness test is a widely recognized empirical indentation hardness test method. It determines the hardness of a material by measuring the permanent depth of indentation caused by a specific indenter under a defined load. Unlike the Brinell test, which measures the diameter of the indentation, the Rockwell method focuses on the differential depth, making it faster and easier to read directly from the testing machine.

How to Use the Rockwell Hardness Calculator

Using this tool is straightforward. First, select the appropriate scale for your material. For example, Scale C (HRC) is typically used for hard steels and titanium alloys, while Scale B (HRB) is suited for softer alloys like aluminum or brass. Enter the permanent indentation depth (measured in millimeters) that remains after the major load has been removed and the minor load is still applied. Click "Calculate Hardness" to see the Rockwell number based on the standardized formula: HR = N - (h / s).

Understanding Scales and Constants

Each Rockwell scale uses specific constants (N and s). For the C scale, the constant N is 100 and s is 0.002 mm. For the B scale, N is 130 and s is 0.002 mm. A smaller indentation depth results in a higher hardness value, indicating a more resistant material. This calculator automates these conversions, providing instant results for quality control and material engineering tasks.

Frequently Asked Questions

Why are there different scales? Different materials require different loads and indenters. Using a diamond cone on soft lead would penetrate too deeply, while a steel ball on hardened tool steel might deform the ball itself. What is the difference between HRA and HRC? Both use a diamond cone, but HRA uses a 60kg load whereas HRC uses 150kg, making HRA better for thin materials or shallow cases.