Types of Rockwell Tests

There are two types of Rockwell tests:

• Regular Rockwell: the minor load is 10 kilograms of force (kgf) and the major load is 60, 100 or 150 kgf.

• Superficial Rockwell: the minor load is 3 kgf and major load is 15, 30 or 45 kgf.

In both tests, the indenter may be either a diamond cone or steel ball, depending on the characteristics of the material being tested.

Rockwell Scales:

Rockwell hardness values are expressed as a combination of a hardness number and a scale symbol representing the indenter and the minor and major loads.

The hardness number is expressed by the symbol HR and the scale designation. There are 30 different scales.

The majority of applications are covered by the Rockwell C and B scales for testing steel, brass and other metals. However, the increasing use of materials other than steel and brass, as well as thin materials, necessitates a basic knowledge of the factors that must be considered in choosing the correct scale to ensure an accurate Rockwell test.

The choice is not only between the regular hardness test and superficial hardness test, with three different major loads for each, but also between the diamond indenter and the 1⁄16, 1⁄8, 1⁄4 and 1⁄2-inch diameter steel ball indenters.

If no specification exists or there is doubt about the suitability of the specified scale, an analysis should be made of the following factors that control scale selection:

• Type of material

• Specimen thickness

• Test location

• Scale limitations