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A mechanical pencil sharpener is hand powered.
A common, portable variety is usually small, about 1 inch (2.5 cm) in size, and has no moving parts. One inserts the tip of the pencil into one of the holes, and twists the sharpener or the pencil while holding the other motionless. A blade inside the sharpener shaves the wood of the pencil, thus sharpening the tip. Such sharpeners can be bare or enclosed in a container to collect the shavings. The base of such a sharpener is often made of magnesium.
There are also larger stationary mechanical sharpeners, powered by a crank. These are often screwed or bolted to a wall or desk. One sticks the pencil into the opening with one hand and turns the crank with the other. This rotates a set of cylindrical burrs in the mechanism, set at an angle to each other; this quickly sharpens the pencil. The casing of the sharpener is a repository for the pencil shavings; it needs to be emptied periodically. This type of mechanism was long the standard in offices, schools, and libraries before electric sharpeners became common, and these sturdy devices are still found.
Electric pencil sharpeners work on the same principle as mechanical ones, but the blade is rotated rapidly by an electric motor. Some electric pencil sharpeners are powered by batteries, rather than by electrical plugs, making them more portable.
Specialized sharpeners are available that operate on non-standard sizes of pencil, such as large art pencils used in primary schools and carpenters' rectangular pencils.
Sharpeners of similar design for use on wax crayons are also available, and often included in boxes of crayons.
Since mechanical pencil s dispense the graphite stick progressively as it is used, they do not require sharpening and are usually made of some unsharpenable material such as plastic or metal. Such pencils are sometimes called "self-sharpening pencils."
Pencils were in use before the development of devices specifically to sharpen them. Previously, they were sharpened by shaving with a knife. Pencil sharpeners made this task much easier and gave a more uniform result.
Bernard Lassimone, a French mathematician, applied for the first patent (french patent #2444) on pencil sharpeners, in 1828. In 1847, Therry des Estwaux invented the manual pencil sharpener. One source claims that the Hammacher Schlemmer Company of New York offered the world's first electric pencil sharpener, as designed by Raymond Loewy, sometime in the early 1940sCenturies: 19th century 20th century 21st century Decades: 1890s 1900s 1910s 1920s 1930s 1940s 1950s 1960s 1970s 1980s 1990s Years: 1940 1941 1942 1943 1944 1945 1946 1947 1948 1949 Events and trends Technology First nuclear bomb First cruise missile, the. (Source - about.com)
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