1. Rockwell Hardness Test https://pursuitengineering. blogspot

2. Rockwell Hardness Test
The Rockwell Hardness test is a hardness measurement based on the net increase in depth of impression as a load is applied. Hardness numbers have no units and are commonly given in different scales. The higher the number in each of the scales means the harder the material.
The Rockwell hardness test does not serve well as a predictor of properties such as strength or resistance to scratches, abrasion, or wear, and should not be used alone for product design specifications.
The Rockwell hardness test is used to measure the hardness of metal measures resistance to penetration, the depth of the impression is measured rather than the diametric area..

3. Rockwell Typical Scale Properties

4. Types of indenters used
Conical diamond with a round tip for harder metals to ball indenter’s ranges with a diameter ranging from 1/16” to 1/2” for softer materials. 
In both tests, the indenter may be either a diamond cone or steel ball, depending upon the characteristics of the material being tested
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

5. Types of the Rockwell Test
There are two types of Rockwell tests:
Rockwell: the minor load is 10 kgf, the major load is 60, 100, or 150 kgf.
Super Rockwell: the minor load is 3 kgf and major loads are 15, 30, or 45 kgf.

6. Principe of the Rockwell Test
The indenter moves down into position on the part surface
A minor load is applied and a zero reference position is established
The major load is applied for a specified time period (dwell time) beyond zero
The major load is released leaving the minor load applied
The resulting Rockwell number represents the difference in depth from the zero reference position as a result of the application of the major load

7. Test Procedure Performing a Rockwell test consists of
Putting gently the specimen in contact with the indenter
Applying a minor load
Automatically or manually zero the penetration measuring instrument or dial gage
Applying gradually the major load
Removing gently the total load while leaving in place the preliminary one (so that the elastic deformation following the removal of final load is recovered)
Measuring the depth of penetration using the Instrument

8. Considerations for Test
Require clean and well positioned indenter and anvil
The test sample should be clean, dry, smooth and oxide-free surface
The surface should be flat and perpendicular to the indenter
Low reading of hardness value might be expected in cylindrical surfaces
Specimen thickness should be 10 times higher than the depth of the indenter
The spacing between the indentations should be 3 to 5 times of the indentation diameter
Loading speed should be standardized
No specimen preparation required
Hardness value directly readable, no optical evaluation required
Quick & cost-effective process
Non-destructive testing
Not always the most accurate hardness testing method
The test location must be completely free of all contamination (e.g. scale, foreign bodies or oil)
The indenter has unknown effects on the test results
With increasing hardness, it becomes increasingly difficult to distinguish between materials