Is Hardness Test destructive or Non Distructive

[Nabeel Ahmed Qureshi]

I would like to have clarification on the subject that Hardness testing is classified as a distructive testing technique. Some times it is classified as NDT. Apparently by its nature it shall be a NDT as we mostly perform this test on finished products w/o damaging them.
This was aquestion asked in one of a test papers on NDTs.

[mechcolor]

As per ASNT, hardness testing can be considered a non-destructive test as it does not impair the mechanical integrity of the test piece but due to the dent created on the surface, it cannot be declared as truly a non-destructive testing.

See this what ASNT says:
"Hardness testing by indentation provides an interesting test case for the definition of nondestructive testing. Hardness testing machines look somewhat like drill presses. The applied force is controlled as the bit is lowered to make a small dent in the surface of the test piece. Then the diameter or depth of the dent is measured. The force applied is correlated with the dent size to provide a measurement of surface hardness. The future usefulness of the test piece is not impaired, except in rare cases when a high degree of surface quality is important. However, because the piece's contour is altered, the test is rarely considered nondestructive. A nondestructive alternative to this hardness test could be the use of electromagnetic nondestructive testing."

[Nabeel Ahmed Qureshi]

Thanx for the clarification.