physics

Mechanical pencil

Mechanical pencil is a physics topic covered in the lgStudy science library. This page brings together a partial reference excerpt, illustrations, worked examples, real-world applications and a short study plan, so you can understand Mechanical pencil rather than just read about it. In short: A mechanical pencil or clutch pencil is a pencil with a replaceable and mechanically extendable solid pigment core called a "pencil lead" (), which is often made of graphite and not bonded to the outer casing, thus the user can mechanically extend it, as it is worn away from use. Mechanical pencils often include erasers.

Key takeaways

Mechanical pencil belongs to physics; place it in that map before memorising details.
Learn the definition first, then one example that makes the definition concrete.
Connect Mechanical pencil to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of Mechanical pencil from memory before moving on to harder problems.

Reference excerpt

A mechanical pencil or clutch pencil is a pencil with a replaceable and mechanically extendable solid pigment core called a "pencil lead" (), which is often made of graphite and not bonded to the outer casing, thus the user can mechanically extend it, as it is worn away from use. Mechanical pencils often include erasers. Mechanical pencils were first used in the 18th century. The first mass-produced mechanical pencil, the Eversharp (originally "Ever Sharp"), was patented in 1913 by Charles R. Keeran Other names include: microtip pencil, automatic pencil, drafting pencil, technical pencil, draughting pencil, click pencil (generally refers to a specific brand), pump pencil, leadholder, Pacer (Australian English, ca. the 1980s), propelling pencil (British and Australian English, often refers to higher-end mechanical pencils), pen pencil (Indian English), and lead pencil (Bangladeshi and American English). Mechanical pencils are used to provide lines of constant width, without need of sharpening, for tasks such as technical drawing as well as for clean looking writing. They are also used for fine-art drawing. Since they do not have to be sharpened, they are also popular with students.

History

Conrad Gessner described a lead holder pencil in 1565, but the lead had to be manually advanced and sharpened. The earliest extant datable example of a mechanical pencil was found aboard the wreckage of HMS Pandora, which sank in 1791. The first patent for a refillable pencil with lead-propelling mechanism was issued to Sampson Mordan and John Isaac Hawkins in Britain in 1822. After buying out Hawkins' patent rights, Mordan entered into a business partnership with Gabriel Riddle from 1823 to 1837. The earliest Mordan pencils are thus hallmarked SMGR. After 1837, Mordan ended his partnership with Riddle and continued to manufacture pencils as "S. Mordan & Co". His company continued to manufacture pencils and a wide range of silver objects until World War II, when the factory was bombed. Between 1822 and 1874, more than 160 patents were registered pertaining to a variety of improvements to mechanical pencils. The first spring-loaded mechanical pencil was patented in 1877. Two of the most popular 19th-century lead sizes were 1.5 and 1.03 mm, "VS" and "M", respectively. Many other sizes were in use, however, before the Eversharp's success made its .046 inch lead size a de facto standard (this size has been variously metricized as 1.1, 1.18, and 1.2 mm, all nominal sizes). Thinner .036 inch (0.9 mm) lead was introduced in the later 1930s and gradually became the new standard, eventually being displaced by 0.7 mm. Many thinner sizes later became available, as well as thicker leads such as 1.4 and 2.0 mm. The first modern mechanical pencil was the Eversharp (originally "Ever Sharp"), invented by Charles R. Keeran who applied for the key patent in 1913. It has been described as "the first mass-produced mechanical pencil to combine a simple propelling mechanism with large lead capacity and robust, ergonomically sound design ... that redefined the mechanical pencil as a mass-market product, to the extent that "eversharp" came to be widely used as a generic term for a mechanical pencil." More that 12,000,000 Eversharp pencils had been sold by the early 1920s, and its design was widely copied. A pioneering mechanical pencil in Japan was invented in 1915 by Tokuji Hayakawa, a metalworker who had just finished his apprenticeship. It was patented in Japan in 1920 and marketed as the "Ever-Ready Sharp Pencil". Although it has been claimed that large numbers were sold, surviving Ever-Ready Sharps are rare. In 1923, the Hayakawa Brothers factory was destroyed in the Great Kantō earthquake. By 1924, Tokuji Hayakawa had turned his attention to the manufacture of radios, but his first invention was immortalized in the name of his new company: Sharp.

Mechanism types

… excerpt ends here. Continue reading the full article.

Illustrations

Worked examples

Example 1 — a first encounter with Mechanical pencil

Start with the simplest possible case. Write down what Mechanical pencil claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In physics, the smallest case is usually a single object, a single equation or a single measurement. Check that every symbol or term in your sentence has a meaning in that case.

Example 2 — changing one variable

Take the situation from Example 1 and change exactly one quantity: double it, halve it, or set it to zero. Predict what should happen to Mechanical pencil before you calculate. Comparing your prediction with the result is the fastest way to find out whether you understand the idea or only the words.

Example 3 — an exam-style question

Typical questions about Mechanical pencil ask you to (a) state it precisely, (b) apply it to given data, and (c) explain a limitation. Practise writing all three answers in under five minutes; the third part is what separates a full-mark answer from an average one.

Applications of Mechanical pencil

In research: Mechanical pencil appears in physics research whenever the underlying quantities have to be modelled precisely. Papers usually cite it as a starting assumption and then explore where it breaks down.
In technology and industry: Engineering practice reuses Mechanical pencil in design rules, simulations and safety margins. Knowing the idea lets you read a specification sheet and understand why the numbers look the way they do.
In the classroom: Mechanical pencil is common in secondary-school and first-year university syllabi. It links to neighbouring topics Mechanisms (engineering), Pencils, Writing implements, so understanding it makes those chapters shorter.
In everyday life: Look for Mechanical pencil outside the textbook — in sport, cooking, traffic, electronics or the sky above you. An example you found yourself is remembered far longer than one you were given.

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How to study Mechanical pencil in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what Mechanical pencil means in your own words.
Compare your version with the excerpt and mark what you missed.
Work through the three examples above with pen and paper.
Explain Mechanical pencil out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is Mechanical pencil in simple terms?

Why does Mechanical pencil matter?

Because it connects several physics ideas at once: it gives you a definition you can apply, a quantity you can calculate, and a way to check whether a result is plausible.

How should I study Mechanical pencil?

Read the excerpt, restate it from memory, then work through the examples and applications listed on this page. The five-step study plan above takes about twenty minutes.

What does this page cover?

It gives you a compact reference excerpt plus original lgStudy explanations, examples, applications and study material on Mechanical pencil.