Serration
Encyclopedia
Serration generally refers to a saw
Saw
A saw is a tool that uses a hard blade or wire with an abrasive edge to cut through softer materials. The cutting edge of a saw is either a serrated blade or an abrasive...

-like appearance or a row of sharp or tooth-like projections. A serrated cutting edge has many small points of contact with the material being cut. By having less contact area than a smooth blade or other edge, the applied force at each point of contact is relatively greater and the points of contact are at a sharper angle to the material being cut. This causes a cutting action that involves many small splits in the surface of the material being cut, which cumulatively serve to cut the material along the line of the blade.

Serration is common both in nature and in man-made objects. In nature, serration is commonly seen in the cutting edge on the teeth of some species, usually sharks. However, it also appears on non-cutting surfaces, for example in botany where a toothed leaf margin or other plant part is described as being serrated. Just as the serrated edge of a knife provides many small points of entry from which to apply a concentrated cutting force, a serrated leaf edge provides a more concentrated force against wind and other natural elements.

Human uses of serration have copied those found in nature. For example, a notch on a saw
Saw
A saw is a tool that uses a hard blade or wire with an abrasive edge to cut through softer materials. The cutting edge of a saw is either a serrated blade or an abrasive...

 or other serrated blade
Serrated blade
A serrated blade is a type of blade used on saws and on some knives or scissors. It is also known as a dentated, sawtooth, or toothed blade.A serrated blade has a cutting edge that has many small points of contact with the material being cut...

 serves the same cutting purpose as the serration of an animal tooth. Serration also appears in the profile of a screw thread cross section in extrusion
Extrusion
Extrusion is a process used to create objects of a fixed cross-sectional profile. A material is pushed or drawn through a die of the desired cross-section...

. The feature is also found in airframe shapes used in certain stealth aircraft
Stealth aircraft
Stealth aircraft are aircraft that use stealth technology to avoid detection by employing a combination of features to interfere with radar as well as reduce visibility in the infrared, visual, audio, and radio frequency spectrum. Development of stealth technology likely began in Germany during...

, which use the jaggedness of the serrated edge to confuse radar signals.
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