Definition 1 of 2
Definition
A small hole drilled at the end of a slot, slit, or at the inside corner of a sharp cutout in a sheet-metal or structural part. The hole spreads stress over a curved edge so the part does not crack at that point under load or vibration.
Plain English
A small round hole drilled at the end of a cut or sharp inside corner to stop the metal from cracking there.
Context Anchor
Seen in aircraft maintenance and sheet-metal repair work, especially around cracks, cutouts, bends, and repair patches.
Derivation
The word relief here means easing or reducing. The hole 'relieves' the concentrated stress that would otherwise build up at the sharp end of a cut or corner.
Why Pilots Care
Prevents introduced weaknesses from becoming fatigue points that could lead to in-flight structural issues.
Analogy
A sharp tear in paper keeps ripping easily, but a round hole at the end of the tear can make it harder for the rip to keep traveling. A relief hole works on a similar idea in aircraft metal.
Intuition Check
Do not think of “relief” here as comfort or pressure release for a person. In this maintenance use, it means easing stress in the material so a crack or tear is less likely to grow.
Example Sentence 1
The mechanic drilled a small relief hole at the end of the crack to keep it from spreading any further.
Example Sentence 2
Adding relief holes along the edge allowed the aluminum to form cleanly without cracking.