Definition
A rough, raised edge or small projection of metal left on a workpiece after cutting, drilling, filing, punching, or shearing. Burrs must be removed (deburred) before a part is assembled or installed, because they can cause cracks, poor fits, injury, electrical shorts, or stress concentrations that lead to component failure.
Plain English
The sharp, ragged little ridge of metal left behind after you cut or drill something. It needs to be smoothed off before the part is used.
Context Anchor
Seen in aircraft maintenance when inspecting drilled holes, trimmed sheet metal, cut tubing, or any part that has been shaped or repaired.
Derivation
From Middle English 'burre,' meaning a rough edge or prickly seed head. The image is the same in the shop: a small, rough thing clinging to the edge of something otherwise smooth.
Why Pilots Care
Unremoved burrs create stress concentrations that can start cracks, interfere with part fits, or damage seals on critical airframe components.
Analogy
A burr is like the sharp edge left on a piece of plastic after you cut it with a knife. The main shape may be correct, but the leftover rough edge still needs to be smoothed off.
Intuition Check
Do not think of a burr as just dirt, a scratch, or normal wear. A burr is raised material that should usually be removed so the part is smooth and safe.
Example Sentence 1
After drilling the rivet holes in the skin panel, the technician deburred each hole to remove any burrs before installing the rivets.
Example Sentence 2
A burr left on the spar flange could damage the skin during assembly and lead to future fatigue.