Technical drawing tool

The ancient Egyptians are known to have used wooden corner rulers. Ancient Nuragic people in Sardinia used compasses made of bronze, like the one displayed in showcase 25 in the Nuragic department of the National Archeological Museum G. A. Sanna in Sassari. In ancient Greece, evidence has been found of the use of styli and metal chisels, scale rulers and triangle rulers. Excavations in Pompeii have found a bronze tool kit used by the Romans, which contained triangle rulers, compasses and a ruler to use with a pen. Although a variety of styli were developed in ancient times and were still being used in the 18th century, quills were generally used as the main drawing tool. Styli were also used in the form of ivory or ebony pencils. Protractors have been used to measure and draw angles and arcs of a circle accurately since about the 13th century, although mathematics and science demanded more detailed drawing instruments. The adjustable corner ruler was developed in the 17th century, but a feasible screw-tightened version not until the 1920s. In the 17th century, a stylus that could draw a line with a specific width called a ruling pen was developed. The stylus had two curved metal pieces which were joined by a screw. Ink was trickled between the blades, from which it flowed evenly across the paper. The basic model was maintained for a long time, with minor modifications, until the 1930s when the German technical drawing pens came to the market. Artists (including Leonardo da Vinci and Albrecht Dürer, Nicholas Bion and George Adams) generally made drawing tools for themselves. Industrial production of technical drawing instruments started in 1853, when Englishman William Stanley (1829–1909) founded a technical manufacturing company in London. Even then, however, most tools were still made by hand. In the 1930s the equipment available expanded: drawing apparatus and Rapidograph-drawing pens appeared, improving the line quality and, especially, producing consistent line width. In addition to the Rapidograph stylus, a more traditional Grafos-type stylus was used for a long time, where different line widths were achieved by changing the pen nib. For instance in Finland Grafos was commonly used as a primary drawing tool still in the early 1970s. Equipment changed radically during the 1990s, when computer-aided design almost completely ousted drawing by hand. Technical design has changed from drawing by hand to producing computer-aided design drawings, where drawings are no longer "drawn", but are built from a virtually-produced model. Drawings are not necessarily produced in hard copy at all, and if they are needed they are printed automatically by a computer program. Hand-drawn designs however are still widely used in the draft design stage. == Drawing tools ==

Pencil Traditional and typical styli used for technical drawing are pencils and technical pens. Pencils in use are usually mechanical pencils with a standard lead thickness. The usual line widths are 0.35 mm, 0.5 mm, 0.7 mm and 1.0 mm. Hardness varies usually from HB to 2H. Softer lead gives a better contrast, but harder lead gives a more accurate line. Bad contrast of the lead line in general is problematic when photocopying, but new scanning copy techniques have improved the final result. Paper or plastic surfaces require their own lead types. In most cases, the final drawings are drawn with ink, on either plastic or tracing paper. The pen is generally a Rapidograph-type technical pen, a marker pen that draws lines of consistent width (so-called steel marker pen). The pen has an ink container which contains a metal tube, inside which is a thin metal needle or wire, the soul. Ink is absorbed between the needle and the tube wall, preventing an excessive amount of ink from being released. The needle has a weight and by waving the pen back and forth the needle is released and the ink can run. Originally, the tank was filled from an ink bottle; newer pens sometimes alternatively use ink cartridges. Each line width has its own stylus. The line width is standardized: In Finland, the most commonly used set is , , , , and . Separate styli are used for tracing paper and plastic, because plastic requires a harder pen tip. To function well they require regular maintenance, the finest marker pens in particular. Drafting board The drawing board is an essential tool. Paper will be attached and kept straight and still, so that the drawing can be done with accuracy. Generally, different kind of assistance rulers are used in drawing. The drawing board is usually mounted to a floor pedestal in which the board turns to a different position, and also its height can be adjustable. Smaller drawing boards are produced for table-top use. In the 18th and 19th centuries, drawing paper was dampened and then its edges glued to the drawing board. After drying the paper would be flat and smooth. The completed drawing was then cut free. == Drawing materials ==

Drafting paper Silk-paper-like translucent drafting paper that wrinkles when wetted. It is primarily suitable for pencils and felt tip pens. Pencil marks can be corrected to some extent with an eraser. Thick draft paper Sandwich-paper-like, thin translucent sheet of paper. Manufactured in different strengths, the surface may be slightly polished. This paper also wrinkles upon wetting. Suitable for pencil and felt tipped pens, and with limitations for technical pens. An eraser can be used for pencil lines. Ink is difficult to erase without damage. Cloth Drafting linen was formerly used for technical drawings. It was durable and held up to handling, but it was difficult to use in modern whiteprints for reproduction, and shrinking was a concern. Tracing paper Polished sandwich paper-like, translucent thick paper, which comes in different strengths. Wrinkles upon wetting. Suitable for both graphite pencils and technical pens. An eraser or sharp scraper tool is used for corrections. Tracing tube Translucent plastic film, which is usually of gray or a light khaki shade. Common types are 0.05, 0.07 and 0.10 mm thick. These films are also used in photocopying. The most commonly used materials are polyesters, and sometimes also PVC or polycarbonate; arguably, a proprietary eponym or genericized trademark for this is called Mylar. Inks Drawing inks can be divided into two groups: India ink and polymer inks. India ink is used on paper and drafting film plastics. The most commonly used India ink is a colloidal mixture of water and carbon black. Dry transfer Dry transfer decals can speed the production of repetitive drawing elements such as borders, title blocks, line types, shading, and symbols. They were frequently used in the production of schematic drawings, maps, and printed circuit board artwork, for example. Dry transfer lettering such as Letraset was used especially in lettering larger size document annotations, or when consistency of lettering was especially required. ==Reproduction==

Many copies of technical drawings may be required in the construction of a project. Reproductions must be accurate as to size and shape, but for many purposes need not be permanent. The blueprint process was first used for mechanical reproduction of drawings. Drawing offices may use diazo or whiteprint processes. Where the volume of drawings reproduced justifies the cost of the machine, a large format photocopier using xerography can reproduce drawings at lower cost than re-plotting them. == See also ==