Mechanical pencil#Types

Image: Sampson Mordan 1822 pencil-holders patent.png

Conrad Gessner described a lead holder pencil in 1565, but the lead had to be manually adjusted to sharpen it.Henry Petroski, The Pencil:A History of Design and Circumstances, Random House, 2011 Random House, 2011 {{ISBN|0307772438}} The earliest extant datable example of a mechanical pencil was found aboard the wreckage of HMS Pandora, which sank in 1791.National Geographic Magazine, Vol. 168, No. 4 (October 1985), p. 450 (illustrated p. 451)

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.{{cite web | url = http://www.leadholder.com/main-history.html | archive-url = https://web.archive.org/web/20070824085520/http://www.leadholder.com/main-history.html | url-status = dead | archive-date = 24 August 2007 | title = History of Leadholders | publisher = Leadholders.com | date = 4 January 2008 | accessdate = 27 February 2008 }}{{cite web | url=http://markhillcollects.blogspot.com/2009/04/sampson-mordan-pencils.html | title=Sampson Mordan Pencils| publisher=Mark Hill Collects: The 20th Century Design and Collectibles Blog| date=30 April 2009 | accessdate=12 December 2009}} 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 are now 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.{{patent|US|1130741|"C. B. Keeran, Lead Pencil, Application Filed Oct.10, 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."{{cite journal | url = http://www.vintagepens.com/Eversharp_history.htm | title = A Tale of Two Pencils: Keeran's Eversharp & Hayakawa's Ever-Ready Sharp | journal = The PENnant | date = Winter 2001 | first = David | last = Nishimura | publisher = Pen Collectors of America}} 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.{{cite web | url = http://sharp-world.com/corporate/info/his/only_one/index.html | work = Product Story | title = 1915: Hayakawa Mechanical Pencil | publisher = SHARP Corporate | date = | access-date = 8 August 2015}}{{cite web | url = http://sharp-world.com/corporate/info/his/h_company/1915_1919/index.html | title = 1915-1919 : Invention of Ever-Sharp Pencil | publisher = SHARP Corporate | date = | access-date = 30 March 2009}} 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.

Some present-day manufacturers are: Pentel, Pilot, Tombow, Uni-ball and Zebra of Japan; Faber-Castell, Lamy, Rotring and Staedtler of Germany; Koh-i-Noor Hardtmuth of the Czech Republic; Bic of France; Monami of South Korea; PaperMate and Parker of USA; Caran d'Ache of Switzerland and numerous Chinese as well as other Asian and European manufacturers.

Image:Mechpencil05.jpg Sharp ratchet drafting pencil disassembled, showing three 0.5 mm graphite leads.]]

Image:Staedtler 925-25 05 Mechanical Pencil.JPG 925-25 05, assembled (top) and disassembled (bottom).]]

File:Pentel Graphgear 0.5mm explosion.jpg

File:Rotrinclose.jpg 600 metal body with matte coating.]]

Mechanical pencils can be divided into two basic types: those that both hold the lead and can actively propel it forward, and those that only hold the lead in position.

Screw-based pencils advance the lead by twisting a screw mechanism, which moves a propelling pin or lead carrier down the barrel of the pencil. Lead is not fed from an internal reservoir, but must be replaced manually, usually from the front. This was the most common type up until the earlier part of the mid-twentieth century. Most have a mechanism that retracts the lead when twisted the other way, but many older designs do not and the lead must be pushed back into the pencil manually.

A clutch pencil (or leadholder) tends to use thicker leads (2.0–5.6 mm) and generally holds only one piece of lead at a time. A typical clutch pencil is activated by pressing the eraser cap on the top, to open the jaws inside the tip and allow the lead to freely drop through from the barrel (or back into it when retracting). Because the lead falls out freely when the jaws are opened, its forward movement cannot be controlled except by external means. This can be easily done by keeping the tip of the pencil a few millimeters above a work surface or the palm of one's hand. Some clutch pencils do have mechanisms which incrementally advance the lead, such as the Alvin Tech-Matic leadholder, but these are not normally considered to be in the same category as most pencils with propelling mechanisms.

Ratchet-based or "repeater" pencils are a variant of the clutch pencil, in which the lead is held in place by two or three small jaws inside a ring at the tip. The jaws are controlled by a button on the end or the side of the pencil. When the button is pushed, the jaws move forward and separate, allowing the lead to advance. When the button is released and the jaws retract, the "lead retainer" (a small rubber device inside the tip) keeps the lead in place, preventing the lead from either falling freely outward or riding back up into the barrel until the jaws recover their grip. Other designs use a precisely-fitted metal sleeve to guide and support the lead, and do not need a rubber retainer.

In one type of ratchet-based pencil, shaking the pencil back and forth causes a weight inside the pencil to operate a mechanism in the cap. A button may be present on the top or side of the pencil, to allow the user to advance the lead manually when necessary. Another variation advances the lead automatically. In this design, the lead is advanced by a ratchet but only prevented from going back into the pencil, just held from falling by a small amount of friction. The nib is a spring-loaded collar that, when depressed as the lead is worn away, extends out again when pressure is released.

An advanced ratchet type has a mechanism that rotates the pencil lead 9 degrees counter-clockwise every time the lead is pressed on to the paper (which counts as one stroke), to distribute wear evenly. This auto-rotation mechanism keeps the lead 50% narrower than in the common propelling mechanical pencils, resulting in uniform thickness of the lines written onto the paper. The design was first patented by Schmidt of Germany, and later developed by Mitsubishi Pencil Company of Japan, and named Kuru Toga under the Uni brand.[http://www.mpuni.co.jp/product/category/sharp_pen/kurutoga/index.html Kurutoga Website] Kuru Toga, which in Japanese, means "spinning to a taper". {{webarchive |url=https://web.archive.org/web/20090919122735/http://www.mpuni.co.jp/product/category/sharp_pen/kurutoga/index.html |date=19 September 2009 }} This type of pencil is most suited for Asian languages that have multiple strokes per letter or word, where the pencil is frequently lifted off the paper. The mechanism is less suitable for cursive writing used in western scripts. Another recent auto-rotation movement by Uni rotates the lead 18 degrees per stroke (or 20 strokes per complete revolution), which is better suited for western scripts.

There exist protection mechanisms that prevent the lead from breaking (within certain limits) when excessive pressure is exerted while writing. A mechanism employed in the DelGuard system by Zebra of Japan causes the lead sleeve to extend outward when excessive pressure is applied at an angle. When excess vertical pressure is applied on the lead, the lead is automatically retracted inwards.

Higher-end mechanical pencils often feature a lead hardness grade indicator and sometimes feature a retractable lead guide pipe. This allows the lead guide pipe to retract back into the pencil body, which will keep it protected in storage and during transit and makes it 'pocket-safe'.

File:Faber-Castell TK lead sharpener and 2 mm pencil lead.jpg and 2mm pencil lead in a clutch-type leadholder.]]

File:Caran dache fixpencil 0012.jpg holder by Caran d'Ache.]]

In spite of the name, pencil leads (also called cores) do not contain the toxic chemical element lead, but are typically made with graphite and clay, or plastic polymers. The downside of mechanical leads are that they are not as strong as traditional pencils. Wooden pencil lead is bonded to the outer wooden case, therefore providing more lead protection and strength. This changed in 1962, when Pentel launched new mechanical pencils with the diameters of 0.5mm and 0.7mm. These pencils contained a new type of lead formulated with polymers that act as a binder to strengthen the lead. This polymer replaced the clay in mechanical pencil lead and made it easier for manufacturers to produce lead with smaller diameters.{{Cite web |last=Sola |date=2014-12-15 |title=Pentel Black Polymer 999 |url=https://pencilsandotherthings.wordpress.com/2014/12/15/pentel-black-polymer-999/ |access-date=2023-08-01 |website=pencils and other things |language=en}}{{Cite web |title=製品開発ストーリー シャープ用替芯 |url=https://www.pentel.co.jp/corporate/product-story/lead-mechanicalpencil/ |access-date=2023-08-01 |website=ぺんてる株式会社 |language=ja}}

Compared to standard pencils, mechanical pencils have a smaller range of marking types, though numerous variations exist. Most mechanical pencils can be refilled, but some inexpensive models are meant to be disposable and are discarded when empty.

File:Lead container.jpg

File:A container of 0.50 milimeter polymer mechanical pencil leads 20230315 184725.jpg

Mechanical pencil mechanisms use only a single lead diameter. Some pencils, such as the Pentel Function 357, place several mechanisms within the same housing, so as to offer a range of thicknesses (in this case three: 0.3, 0.5 and 0.7 mm). 1.00 mm leads also exist, but they are very rare.

Different sizes of lead diameters are available to accommodate various preferences and pencil builds, as shown in the table below. The most common lead sizes are 0.5 mm and 0.7 mm, whose line widths provide a favourable balance between precision and strength. Less common lead sizes can range from 0.2 mm up to 5.6 mm. Pentel has also previously demonstrated a prototype 0.1 mm pencil.{{Cite web|url=http://www.nichima.co.jp/news/entry/1747.html|title=ニュース - 文マガ|website=www.nichima.co.jp|access-date=7 May 2017}}

Pencils with sub-millimeter leads can usually hold multiple leads at the same time, reducing the frequency of refills. One exception was the Pentel 350 E, possibly Pentel's first mechanical pencil,{{cite web |url=http://www.leadholder.com/lh-thin-pentel-350.html |title=Pentel 350 Series Mechanical Pencil {{!}} Leadholder |publisher=Leadholder.com |accessdate=14 November 2010 |url-status=dead |archiveurl=https://web.archive.org/web/20110626050201/http://leadholder.com/lh-thin-pentel-350.html |archivedate=26 June 2011 }} which could only hold a single stick of 0.5 mm lead. Refill leads can be bought in small tubes and inserted into the barrel as needed.

The bracketed values in inches were found by calculation and rounded to 3 decimal places.

The diameters, however, are not exact. The exact diameter is usually slightly larger. The Japanese JIS standard for mechanical pencil leads, states that the actual diameter for "0.5 mm" lead (for example), should range from 0.55 mm to 0.58 mm.

For sub-millimeter diameter leads, the standard length of the cylindrical stick for all grades is 60 mm. However, some manufacturers make leads that are 75 mm long, for selected grades.

As with non-mechanical pencils, the leads of mechanical pencils are available in a range of hardness ratings, depending on the user's desired balance between darkness and durability. A commonly-used mechanical pencil lead is identical in density, but not in thickness to a traditional HB (US#2) pencil lead. The hardness depends on the proportion of polymer or resin and graphite in the lead.{{Cite web |date=2023-07-04 |title=Pencil {{!}} Graphite, Wood & Lead {{!}} Britannica |url=https://www.britannica.com/technology/pencil-writing-implement |access-date=2023-07-28 |website=www.britannica.com |language=en}} It is determined by a numerical scale: the higher the number, the harder the lead. Similarly to standard wooden pencils, the lead is distinguished by grading scales. H stands for hardness; as they are typically harder and produce a light gray color. B stands for blackness; they produce a darker color and are typically softer. F stands for fine; it is in between H and HB on the lead grading scale.{{Cite web |title=Making Sense of Pencil Leads |url=https://cowans.org/blogs/cowans-art-knowledge-know-how/making-sense-of-pencil-leads |access-date=2023-07-29 |website=Cowan Office Supplies |language=en}} Compared to standard pencils that have 24 grades of lead, there are only 10 grades of mechanical pencil lead, ranging from 4H-4B.{{Cite web |title=The Right Pencil Lead Grade and Hardness For Every Scenario {{!}} Unsharpen |url=https://unsharpen.com/best-pencil-lead-grade/ |access-date=2023-07-31 |website=unsharpen.com}}

Mechanical pencils with colored leads are less common, but do exist. Crayola's "Twistable" product line includes two different types of colored pencils (erasable and non-erasable) with mechanical feed mechanisms that are dispensed by twisting, but does not offer refill leads. Several companies such as Pentel, Pilot, and Uni-ball (Mitsubishi Pencil Co.) currently manufacture colored refill leads in a limited range of diameters (0.5 mm, 0.7 mm, or 2.0 mm) for their own products, as well as "variety packs" consisting of different colors of leads for those who want to trial different colors of lead. Koh-i-Noor makes mechanical colored pencils with replaceable leads in 2.0, 3.15 and 5.6 mm sizes.[http://www.penciltalk.org/2009/07/koh-i-noor-2-0mm-leadholders-and-colour-leads Koh-I-Noor 2.0mm leadholders and colour leads]. pencil talk. Retrieved on 14 October 2011.

• Technical drawing tools

{{Reflist|30em}}

• Deborah Crosby, Victorian Pencils: Tools to Jewels, Schiffer Publishing Ltd., Atglen, PA, 1998
• Jonathan A. Veley, "The Catalogue of American Mechanical Pencils", Greyden Press, 2011

{{Sister project links|auto=yes|wikt=yes|commonscat=yes}}

• [http://sharp-world.com/corporate/info/his/only_one/index.html Sharp's history of the mechanical pencil]
• [http://www.vintagepens.com/Eversharp_history.htm History and development of Keeran's and Hayakawa's pencils]
• [https://web.archive.org/web/20061109115543/http://www.leadholder.com/ Leadholder Museum] (History and images of Leadholders)
• [https://web.archive.org/web/20141222022355/http://www.sampsonmordan.com/ Sampson Mordan.] First patent for a mechanical pencil
• [http://www.pantagraph.com/news/local/inventor-never-got-rewards-of-pencil-business/article_1941d5f0-ec13-11e2-83ac-001a4bcf887a.html Inventor never got rewards of pencil business - Pantagraph] (Bloomington, Illinois newspaper)

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