Definition
A measurement procedure used to determine the resistance of a material, typically a metal, to permanent indentation or penetration. A hardened indenter (such as a steel ball or diamond point) is pressed into the material under a specified load, and the size or depth of the resulting indentation is measured and converted to a hardness number on a recognized scale such as Rockwell, Brinell, or Vickers.
Plain English
A workshop test that checks how hard a piece of metal is by pressing a small hard tip into it under a known force and measuring the dent it leaves. A smaller dent means a harder material.
Context Anchor
Seen in aircraft maintenance, especially when checking metal parts, repaired areas, or parts that may have been affected by heat.
Derivation
From 'hard,' meaning resistant to deformation, plus 'test,' meaning a controlled check. The name describes exactly what the procedure does -- it tests hardness by direct, repeatable measurement rather than by feel or guess.
Why Pilots Care
Verifies that critical parts like engine components and landing gear meet strength specifications to prevent failure in flight.
Intuition Check
Hardness does not mean overall strength by itself. Here it means resistance to a controlled dent or penetration at the surface.
Example Sentence 1
After heat-treating the steel fitting, the technician performed a Rockwell hardness test to confirm the part met the manufacturer's specification.
Example Sentence 2
Before installing a new bolt, a hardness test confirmed it met the required specifications for the airframe application.