Technical drawing tools are the tools used for technical drawing, including pens and rulers. Drawing tools may be used for measurement and layout of drawings, or to improve the consistency and speed of creation of standard drawing elements. Many of the tools used for manual technical drawing are obsolescent, where computer-aided drawing has become common.
- Drawing Tools
- Pens
Traditional and typical pens used for technical drawing are pencils and technical pens.
Pencils in use are usually mechanical pencils with a standard lead thickness. General line widths are 0.18 mm, 0.25 mm, 0.5 mm and 0.7 mm. Hardness varies usually from HB to 2H. Softer lead gives a better contrast, but harder lead gives more accurate track. Bad contrast of the lead track in general is problematic at photocopying, but new scanning copy techniques have improved the final result. Paper or plastic surfaces do require their own lead types.
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In most cases, the final drawings are drawn with ink, on either plastic or tracing paper. The pen is generally Rapido graph-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. Previously, the tank was filled from an ink bottle, newer styluses use ink cartridges.
Each line width has its own stylus. Width of the line is standardized: In Finland, the most commonly used set is 0.13 mm, 0.18 mm, 0.25 mm, 0.35 mm, 0.50 mm and 0.70 mm. There are their own style 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
- Drawing 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 cut free. Paper could also be secured to the drawing board with pins. More recent practice is to use self-adhesive tape to secure paper to the board. Some drawing boards are magnetized, allowing paper to be held down by long steel strips. Boards used for overlay drafting or animation may include registration pins or peg bars to ensure alignment of multiple layers of drawing media.
- Drafting Machine
A drafting machine is a device which is mounted to the drawing board. It has rulers whose angles can be precisely adjusted with a controlling mechanism. There are two main types of apparatus: an arm-type parallelogram apparatus based on a hinged arm; and a track-type apparatus which moves on a rail mounted to the top of the drawing board. The accuracy of the arm type apparatus is better in the middle of the board, decreasing towards the edges, whereas a track machine has a constant accuracy over the whole board. The drawing head of a track-type drafting machine slides on bearings in a vertical rail, which in turn is moved along a horizontal, top-mounted rail. Both apparatus types have an adjustable drawing-head with rules attached to a protractor scale so that the angle of the rules may be adjusted.
A drafting machine allows easy drawing of parallel lines over the paper. The adjustable angle between the rulers allows the lines to be drawn in varying accurate angles. Rulers may also be used as a support for separate special rulers and letter templates. The rules are replaceable and they can be for example scale-rules.
Drawing apparatus has evolved from a drawing board mounted parallel ruler and a pantograph, which is a device used for copying objects in an adjustable ratio of sizes.
- Rulers
Rulers used in technical drawing are usually made of polystyrene. Rulers come in two types according to the design of their edge. Straight edge can be used with lead and felt pens, whereas when technical pen is used the edge must be grooved to prevent the spread of the ink.
Architect's scale is a scaled, three-edged ruler which has six different scales marked to its sides. A typical combination for buildings details is 1:20, 1:50, 1:100, 1:25, 1:75 and 1:125. There are their own rulers for zoning work as well as for inch units. Today scale rulers are made of plastic, formerly of hardwood. A pocket-sized version is also available, with scales printed on flexible plastic stripes