How Does a Pencil Sharpener Work?


Pencil Sharpeners Work With the Design of the Pencil

  • For a pencil sharpener to be effective, the pencil must adhere to a standard design. Most pencils are designed at a standard diameter of 8 mm. This diameter consists of a thin graphite lead (pencil lead) core surrounded by soft wood that can easily be whittled away by the pencil sharpener's blades.

Blades Are Affixed at an Angle

  • The blades of a pencil sharpener are affixed at a 23-degree angle to provide a consistently conical shape to the sharpened pencil. Two blades--each at a 23-degree angle--are affixed horizontally with the point where the blades are closest together located to the inside of the pencil sharpener.

Blades Rotate to Sharpen Pencils

  • When a pencil is inserted into a pencil sharpener, it is pushed as far as it will go into the recess created by the horizontally opposed blades. When the blades rotate (rotation can be achieved either manually or by an electric motor), they spin around the pencil and shave away the soft outer wood to expose and shape the graphite lead inside.


  • Early pencil sharpeners consisted only of two blades situated in a metal housing that was manually turned around the pencil. More modern pencil sharpeners include a housing, usually composed of plastic, to catch the soft wood shavings as they are cut away. In these sharpeners, the blades are turned by a hand crank protruding outside the housing, or the pencil is manually turned against the blades. Electric pencil sharpeners rotate the blades through use of an electric motor affixed inside the sharpener housing; a sensor or small switch detects the insertion of a pencil and activates the motor.

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