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Metal Hardness Testing
- Reference Information and Standards -

Metal Hardness Testing provides a standardized measurement for the resistance of a metal to deformation from a small indenting object, frequently made of tungsten or diamond, under a known force.  This hardness measurement provides a simultaneous indication of multiple properties and characteristics of metals in a simple, fast, and relatively non-destructive fashion that can even be performed on the factory floor in some cases.    

rockwell indenter
Rockwell is the most common
type of hardness testing.
Since Hardness testing measures many multiple properties and characteristics of metals, it closely relates to the ability of a metal to react in prescribed ways in real life situations which involve multiple characteristics of metals, such as the ability of a material to avoid wear in certain applications.  And since a hardness tester is measuring multiple characteristics at once and is sometimes dependent on operator measurement the most practical way to verify the performance of a tester is by using test blocks which have been verified to provide certain results.  The hardness test

is the most frequently used metallurgical test and is most commonly employed for testing metals which have had the hardness changed, either by a heat treatment process or sometimes by work hardening as in some sheet metals. 

There are three main types of hardness testing: indentation, rebound, and scratch. 

  • Indentation hardness methods measure the inelastic deformation of a metal  by an indenter pushed into a metal with a defined force oriented normal to the material face.  Indentation hardness covers most of the main metal hardness test methods since it is less affected by surface conditions (roughness, change in hardness)
  • Rebound testing measures the elastic deformation of a surface by a bouncing metal ball.  This method is very portable and has a low cost so it is widely used as a quick measure.  This is the Leeb test.  This bounce measure is correlated to values used in indentation hardness.
  • Scratch hardness uses two forces, an indentation force normal to the surface and a transverse force to move the indenter across the surface, thereby displacing material.  This test is often used on coatings since indentation hardness is affected by the underlying hardness of a supporting material if the measured material is not very thick enough – sometimes 10x the indented thickness.  Scratch hardness testers are not sold by Ernst and Quality Solutions.

Beyond these categories of hardness testing the test methods are based on the ability of a tester to measure the hardness range and metallurgical structure, and even the shape, size, or type of metal. 

And anyone who notices a similarity between the quality solutions logo and the widely seen diagram of a Rockwell test wins a prize.


Rockwell Hardness Chart (+PDF)
(aka Hardness Scale Conversion Chart)

Round Correction Factor (+PDF)
Hardness Minimum Thickness (+PDF)

ASTM Hardness Test Methods (+PDF)
Rockwell Hardness Scales (+PDF)

Brinell Hardness Chart (+PDF)
Vickers Hardness Chart (+PDF)

Rockwell Hardness Testing
Brinell Hardness Testing
Microhardness Testing


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