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A mechanical pencil (US English)〔(mechanical pencil – definition. American English definition of mechanical pencil by Macmillan Dictionary ). Macmillandictionary.com. Retrieved on 2011-10-14.〕 or a propelling pencil (UK English)〔(propelling pencil ). Cambridge Dictionary on-line〕 is a pencil with a replaceable and mechanically extendable solid pigment core called a "lead" . The lead, often made of graphite, is not bonded to the outer casing, and can be mechanically extended as its point is worn away. Other names include automatic pencil, drafting pencil, technical pencil, click pencil, clutch pencil, leadholder, pen pencil (Indian English), lead pencil (Bangladeshi English), and pacer (or spacer), or the most common, pump lead. Mechanical pencils are used to provide lines of constant width without sharpening in technical drawing and in writing quick neat writing. They have also been used for fine-art drawing.〔(【引用サイトリンク】 Artistic Realism Art Studio: Graphite pencil, charcoal and pastels fine art by David and Faith Te, works in progress, and updates to www.artisticrealism.com: Archive for the ‘Pencil Drawing Tutorials’ )〕〔(【引用サイトリンク】 title= ''In the Land of Polio (or Headhunters) he Weeps for and is in Love with the Girl Who Disappeared'', mechanical pencil drawing by Daniel C. Boyer )〕 Mechanical pencils were first used in the 18th century, with many designs patented in the 19th and 20th centuries. ==History== Conrad Gesner described a leadholder 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 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. After 1837, Sampson Mordan ended the 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 and a twist-feed mechanism was developed in 1895. The 0.9 mm lead was introduced in 1938, and later it was followed by 0.3, 0.5 and 0.7 sizes. Eventually, 1.3 and 1.4 mm mechanisms were available, and 0.4 and 0.2 versions are now produced. The mechanical pencil became successful in Japan with some improvements in 1915 by Tokuji Hayakawa, a metal worker who had just finished his apprenticeship. It was introduced as the "Ever-Ready Sharp Pencil". Success was not immediate, since the metal shaft—essential for the pencil's long life—was unfamiliar to users. However, the Ever-Ready Sharp began selling in huge numbers after a company from Tokyo and Osaka made large orders. Later, Tokuji Hayakawa's company got its name from that pencil: Sharp.〔 At nearly the same time in the US, Charles R. Keeran was developing a similar pencil that would be the precursor of most of today's pencils. Keeran's design was ratchet-based, whereas Hayakawa's was screw-based. These two development histories – Hayakawa and Keeran – are often mistakenly combined into one. Keeran patented his lead pencil in 1915 and soon afterwards arranged production.〔 After some improvements, his design was marketed as the "Eversharp" pencil by the Wahl Adding Machine Company; by the early 1920s, Wahl had sold more than 12,000,000 Eversharps.〔 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Mechanical pencil」の詳細全文を読む スポンサード リンク
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