Mechanical pencil

A ratchet-type mechanical pencil

A mechanical pencil is an implement for writing or drawing in which the solid marking core (usually graphite based and called pencil lead, but coloured pigments and other solid substances are also used) is not bonded to the outer casing, and is designed such that the core is to be extended as its point is worn away. Mechanical pencils are known by many alternative names, some of the most common alternatives being propelling pencil, automatic pencil, drafting pencil, technical pencil, clicky pencil, clutch pencil and leadholder.

Mechanical pencils are often designed and used to provide lines of constant thickness without requiring sharpening, making them well suited to applications like technical drawing and writing.

History

The mechanical pencil was invented in Britain in 1822 by Sampson Mordan 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 the 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, 0.3. Even a 1.4 mm mechanism was available, and 0.4 and 0.2 versions are now produced.

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

Metal propelling pencil

A ratchet 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. This was the most common type in the earlier part of the twentieth century.
• 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

Leadholder tip

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 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.

Types of Lead Thickness

Different lead thicknesses are used, depending largely on users' preferences. Generally, the most used leads for mechanical pencils are 0.5mm and 0.7mm. By using such a width, most users will produce a distinct line, allowing sharp writing and drawing. However, due to 0.7mm being thicker than 0.5mm, many users prefer 0.5mm due to the sheer precision and fine trail it produces.

The most commonly available lead thicknesses are 0.3mm, 0.5mm, 0.7mm, 0.9mm and 2mm, but there are more sizes. Like standard pencils, leads for mechanical pencils are available in a range of hardness grades although the range of grades is usually less than with standard pencils.

Further reading

• Deborah Crosby, Victorian Pencils: Tools to Jewels, Schiffer Publishing Ltd., Atglen, PA, 1998.

External links

• Sharp's history of the mechanical pencil
• History and development of Keeran's and Hayakawa's pencil styles
• Dave's Mechanical Pencils (Blog about mechanical pencils. Includes reviews.)
• Leadholder Museum (History and Images of Leadholders)
• Parkercollector.com (Detailed information about most pen models made by the Parker Pen Company.)