Pencil sharpener

A manual prism sharpener.

A pencil sharpener (also referred to as a parer or topper in Ireland) is a device for sharpening a pencil's writing point by shaving away its worn surface. Pencil sharpeners may be operated manually or by an electric motor.

History

Before the development of dedicated pencil sharpeners, a pencil was sharpened by whittling it with a knife. Pencil sharpeners made this task much easier and gave a more uniform result. Some specialized types of pencils, such as carpenter's pencils are still usually sharpened with a knife, due to their flat shape, though recently a fixed-blade device with a rotatable collar has become available.

Bernard Lassimone, a French mathematician, applied for the first patent (French patent #2444) on pencil sharpeners in 1828. In 1847, Therry des Estwaux invented an improved mechanical sharpener. The first American pencil sharpener was patented by Walter K. Foster of Bangor, Maine in 1855.[1] Electric pencil sharpeners for offices have been made since at least 1917.

They now come in a wide array of colors and shapes. It is common for traditional sharpeners to have a case around them to collect the shavings. It can be removed for emptying.

In May 2011 tourism officials in Logan, Ohio put on display, in its regional welcome center, hundreds of pencil sharpeners which had been collected by Rev. Paul Johnson, an Ohio minister who died in 2010. Johnson, a World War II veteran, had kept his collection of more than 3,400 sharpeners in a small shed, outside his home in Carbon Hill in southeast Ohio. He had started collecting after his wife gave him a few pencil sharpeners as a gift in the late 1980s. He kept them organized into categories, including cats, Christmas and Disneyland. The oldest was 105 years old.

Mechanical sharpeners

Prism sharpeners

A hand-cranked prism sharpener

A mechanical pencil sharpener is hand-powered. A common, portable variety is usually small and in the shape of a rectangular prism, about 1 × 5/8 × 7/16 inch (2.5 × 1.7 × 1.1 cm) in size with a conical hole on the small end. A sharp blade is mounted in a recess on the largest side such that its sharp edge just enters the cone. The body of the sharpener is often contoured, ridged or grooved to make it easier to grip firmly. It has no moving parts - the tip of the pencil is inserted into the hole of the sharpener and rotated, while the sharpener is held motionless.

A hand-cranked planetary sharpener with spring-driven pencil holder. The small handle behind the crank is the sharpness regulator.

The blade inside the sharpener shaves the wood of the pencil, thus sharpening the tip, while the shavings emerge through a slot along the blade edge. An important feature is a larger clearance hole at the end of the cone allowing sections of the pencil lead which break away to be removed with only minor inconvenience. Such sharpeners can be bare or enclosed in a container to collect the shavings. Enclosed sharpeners can be harder to clear in the event of a blockage. The base of such a sharpener is often made of aluminum, magnesium or hard plastic. Skill is needed to not break the tip of the pencil being sharpened, losing the result of work immediately. While it is more common in sharpeners with cylindrical cutters, some prism sharpeners are also hand-cranked.

Blade sharpeners

A sharpener that uses a razor blade

Unlike prism sharpeners, blade sharpeners do not rotate around the pencil being sharpened and may be viewed as just a special form of knife with increased safety and convenience. Some models directly hold replaceable shaving razor blades, others have permanently fitted blades. Blade sharpeners may require more skill, but they allow one to sharpen the tip of the pencil into any desired shape, whereas prism sharpeners have a fixed sharpening angle and require circular symmetry. While most blade sharpeners are simple and hand operated, some devices in the past were crank operated, using mechanisms to convert crank rotation into linear motion [2].

Cylindrical cutters

A wall-mounted planetary sharpener (casing removed to reveal the mechanism).

A larger, stationary mechanical sharpener can be mounted on a desk or wall and powered by a crank. Typically, the pencil is inserted into the sharpener with one hand and the crank turned with the other. This rotates a set of cylindrical cutters in the mechanism, set at an angle to each other. This quickly sharpens the pencil, with a more precise finish than the simpler blade device. Advanced models have a spring - driven holder for the pencil (the pencil advances inside the mechanism while being sharpened). Some versions also offer a regulator of the desired sharpness (it is not always optimal to make the graphite core needle-sharp). Such sharpeners may be very easy to use even by children but are much more expensive than prism sharpeners. Some such rotary sharpeners have only one burr cylinder. The casing of the sharpener is the repository for the pencil shavings; it needs to be emptied periodically. They are also called "planetary sharpeners", [3] in reference to their use of planetary gears.

Other systems

Jupiter 1 with rotary disk cutters

Some older models like the 1897 German Jupiter 1 used reversible rotary cutter-disks with cutting edges radiating from the center on each side. These were high-end models, quite large and expensive. Others simply used abrasives like sandpaper. In some cases an abrasive was used to shape the graphite core, while the wood was cut some other way.

Electric sharpeners

Battery-operated sharpener.

Electric pencil sharpeners work on the same principle as mechanical ones, but the cylindrical cutter is (or cutters are) rotated rapidly by an electric motor. Some electric pencil sharpeners are powered by batteries rather than being plugged into a building's electrical system, making them more portable.

Razor knife

Artists use a very sharp knife to sharpen pencils and other media by hand. The tip is cut into a triangle shape and then the edges of the triangle are trimmed down. This requires a total of 6 cuts and takes practice to master without breaking the lead.

Specialized pencil sharpeners

Specialized sharpeners are available that operate on non-standard sizes of pencil, such as the large art pencils used in primary schools. Sharpeners that have two holes, one for normal pencils and one for larger art pencils are still fairly common. Some mechanical sharpeners have a large hole with a rotating disk in front of it that has several holes of different sizes.

An artist's or draftsman's pencil sharpener leaves the graphite untouched and sharpens only the wood. (Some models can switch from standard to wood-only by an adjustment.) The graphite lead is then honed to a razor point with a lead pointer which sharpens only the lead without wood. Lead pointers are also used with mechanical leadholders which have removable/refillable leads.

Sharpeners of similar design for use on wax crayons are also available, and sometimes included in boxes of crayons. These often have plastic blades for the softer wax.

Prism sharpener with two holes

Carpenter's flat pencil sharpener.

Carpenters may use carpenter pencils, the shape of which stops them from rolling away, while still providing a constant line width. These pencils were traditionally sharpened with tools conveniently to hand, such as a plane or sandpaper. Rotating pencil sharpeners are now available for these too, where a rotating plastic collar hold the pencil in position.

Because mechanical pencils dispense the graphite stick progressively during use, they do not require sharpening. Such pencils are sometimes called "self-sharpening". But prolonged writing often causes the graphite stick to become lopsided and dull. Specialized versions of pencil sharpener, known as graphite pointers, may be used by drafters and other mechanical pencil users who need constantly sharp points.

External links

• Antique Pencil Sharpeners
• Collector of pencil sharpeners (in French and partly in English)
• Dutch Collector of pencil sharpeners