A ratchet-type mechanical pencil
A mechanical pencil, propelling pencil or technical pencil is a pencil containing an internal mechanism which pushes or propels the thin graphite lead through the tip. Like standard pencils, there are also mechanical pencils which have a rubber eraser on the end. Mechanical pencils provide lines of consistent thickness, well suited for technical applications such as drafting and writing.
History
The mechanical pencil was invented in Britain in 1822 by Sampson Mordan[1] and Gabriel Riddle. Earliest Mordan pencils are thus hallmarked SMGR. Sampson Mordan continued manufacturing pencils and a wide range of silver objects until World War Two, when their factory was bombed.
Between 1822 to 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 0.7, 0.5 and 0.3 mm versions. Even a 1.4 mm mechanism was available.
Pencil lead for a modern mechanical pencil.
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. The Ever-Sharp began selling in huge numbers, however, after a company from Yokohama made a large order. Later Tokuji Hayakawa's company got its name from that pencil: Sharp.
At nearly the same time, in America, 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 are often combined into one.
Types
A rachet mechanical pencil disassembled, showing three 0.5 mm graphite leads.
A number of different types exist:
- Ratchet-based pencils, in which the lead is advanced by a button on either the end or the side. The button pushes two or three small jaw pieces within the cap forward out of a ring that holds them together as one. The pieces separate, allowing the lead to advance. A small rubber device in the mouth of the tip of the pencil, called a lead retainer, holds the lead in place as the jaws retract, preventing it from either falling free of the pencil or riding back up into the pencil, until the jaws close around the upper portion of the lead.
- A variation of the ratchet-based pencil, in which shaking the pencil back and forth causes a weight inside the pencil to operate a mechanism in the cap. A button may be present.
- 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, pulls out more when pressure is next released.
- Screw-based pencils, in which the lead is advanced by twisting a screw, which moves a slider down the barrel of the pencil.
- Screw-based pencils in which the lead is advanced by friction with the screw.
- Twist-based pencils, in which the lead advances upon twisting the head of the pencil. Many of these have a locking mechanism one way to allow the lead to be pushed back into the pencil.
Most mechanical pencils can be refilled with more graphite but some less-expensive models, especially screw-based designs, are disposable.
Clutch pencil
A Staedtler Mars 780 Leadholder
Clutch pencils (or leadholders) use a thicker solid piece of lead (typically 2-4 mm) and work by pressing down the eraser cap to allow the jaws at the end to open, which in turn allows the lead to freely drop through the barrel. They can typically only hold one whole piece of lead at a time.
The advantage of clutch pencils is that they allow a greater variety of marks to be made.
The disadvantage is that because the lead falls when the jaws are opened, there is no controlled dispensing of the lead and so it is best done a few millimeters over the work surface. However, there are clutch pencils that advance the lead incrementally such as the Alvin Tech-Matic leadholder.
Manufacturers
Footnotes
Further reading
- Deborah Crosby, Victorian Pencils: Tools to Jewels, Schiffer Publishing Ltd., Atglen, PA, 1998.
External links
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