The Rockwell Metal Hardness Scales Explained

The Rockwell hardness test is used to test the hardness of materials. The Rockwell test is usually performed on metals ranging from thin steal all the way to harder metals like Titanium. However, there are multiple scales to test in and these are identified by by a letter ranging from A-V  Each scale uses a different indenter and load to perform the test.

The equation for the Rockwell hardens test for metals is below:  d=depth from zero load point.  N and s = various scale factors that can be found in the chart below.

Rockwell A scale

Used to test: Tungsten carbide.

Rockwell B Scale

Used to test: aluminum, brass, and softer steels

Rockwell C Scale

Used to test: harder steels.

There are other scales that are associated with a Rockwell superficial test. These scales use a lighter loads and shallow impressions to perform the test. These are used on testing very thin metals.

Ames Superficial Hardness Tester
Note: There is only one row of dial numbers for the Ames superficial tester.

SCALEMajor Load(kg)PenetratorTypical Material Tested
15N 15 S Diamond Same materials as standard Rockwell except where shallow penetration is necessary as in:
30N 30 S Diamond-
45N 45 S Diamond-
15T 15 1/16 Ball Shallow case hardened parts. To .010 inch
30T 30 1/16 Ball-
45T 45 1/16 Ball Hard thin material down to .006 inch
15W 15 1/8 Ball-
30W 30 1/8 Ball Cemented Carbides
45W 45 1/8 Ball-
15X 15 1/4 Ball Plastics
30X 30 1/4 Ball-
45X 45 1/4 Ball-
15Y 15 1/2 Ball -
30Y 30 1/2 Ball -
45Y 45 1/2 Ball-

Check out the videos below for tips on using your hardness tester

The Rockwell Metal Hardness Scales Explained

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