Technical Drawing

Also known as drafting, technical drawing is the practice of creating accurate representations of objects for architectural and engineering needs. A practitioner of the discipline is known as a drafter. Today the mechanics of the drafting task have considerably changed through the use of CADD computer systems, but regardless of whether a drawing is drawn manually or with computer assistance, it must be reproducible.

Manual Drafting

Basic drafting procedure consists of placing a piece of paper (or other material) on a smooth surface with right-angle corners and straight sides--typically a drafting table. A sliding straightedge commonly known as a t-square is then placed on one of the sides, allowing it to slide across the side of the table and over the surface of the paper (Figure 2.1). Parallel lines can be drawn by simply moving the t-square and running a pencil or technical pen along the edge. The t-square is also used as a means to hold other tools such as set squares or triangles. To do this, the drafter places one or more triangles of known angles on the t-square (which is itself at right angles to the edge of the table) and then draws lines to the angles chosen on the sheet. Modern drafting tables (which in the United States are rapidly being replaced by CAD stations) come equipped with a parallel rule that is supported on both sides of the table to slide over the tracing paper. Since it is secured on both sides of the drafting table, lines drawn along the edge are parallel.

The drafter also has other tools at his/her disposal that are used to draw curves and circles, including compasses (used for drawing simple arcs and circles) and French curves (which typically consist of a piece of plastic with complex curves on it). Another tool used is the spline, which is a piece of rubber-coated articulated metal that can be manually bent to most curves. Figure 2.2 is an illustration of some of the templates and instruments used in manual drafting.

Drafting templates allow the drafter to consistently recreate recurring objects in a drawing without continuously having to reproduce them from scratch. This is particularly useful when using common symbols: for example, in the context of stagecraft, a lighting designer will typically draw from the United States Institute for Theatre Technology (USITT) standard library of lighting-fixture symbols to indicate the position of a common fixture across multiple positions. Templates can usually be purchased from various vendors, usually customized to a specific task, but it is also not uncommon for a drafter or designer to create customized templates.

This basic drafting system requires an accurate table, and careful attention should be given to the positioning of the tools. A common error is to allow the triangles to push the top of the t-square down slightly, thereby throwing off all the angles. Even tasks as simple as drawing two angled lines meeting at a point require a number of moves of the t-square and triangles. In general, drafting often proves to be a time-consuming process.

A solution to these problems was the introduction of the so-called mechanical drafting machine, an application of the pantograph that allowed the drafter to make an accurate right angle at any point on the page quite quickly. These machines often included the ability to change the angle, thereby removing the need for the use of triangles as well.

In addition to the complete mastery of the mechanics of drawing lines, circles, and text onto paper (with respect to the detailing of physical objects), the drafting effort requires a proficient understanding of geometry, trigonometry, spatial comprehension, and above all a high standard of precision and accuracy as well as close attention to detail.

What Square
Figure 2.1 A drafter using a typical drawing board, t-square, and other instruments (after Muller, Edward J., et al.: Architectural Drawing and Light Construction, 5th ed., Englewood Cliffs: Prentice Hall, 1999).
Construction Tools Names
Figure 2.2 Some of the tools, aids and materials used in manual drafting (from Montague, John: Basic Perspective Drawing: A Visual Approach, 3rd ed., New York: John Wiley and Sons, 1998).


Lettering is used on construction drawings as a means to provide written information. A construction sketch or drawing without lettering rarely communicates an adequate description of the object. It is almost always necessary to provide additional labels, notes, and dimensions to clarify the size, type of materials, and location of the component. Drawings are therefore a means of communication of information to others, and text generally is one of the main mediums to transmit information in the form of notes, titles, dimensions, etc. Lettering should enhance a drawing by making it easy to interpret and pleasant to look at; it should not detract from the drawing or be illegible or unsightly to look at. Legibility and consistency are the key ingredients to good lettering. Architectural lettering is often done using all uppercase letters, and abbreviations are commonly used to save space and drafting time (refer to the abbreviation list in the Appendix). When necessary, specific notes can be placed close to the item being identified or connected to it with leader lines.

Although most of the lettering done today on construction drawings is computer-generated, skill in freehand lettering adds style and individuality to a designer's work. And in any style of lettering, uniformity is important. This applies to height, proportion, strength of lines, spacing of letters, and spacing of words. Letters should be spaced by visually equalizing the background areas between the letterforms and not by mechanically measuring the distance between the extremities of each letter (Figure 2.3). The use of light horizontal guidelines (using a hard lead such as a 4H) should be practiced to control the height of letters, while light vertical or inclined guidelines are required to keep the letters uniform. Words should be spaced well apart, while letters should be spaced closely within words.

A cursory examination of the various alphabets and typefaces in use today clearly shows that the vast majority fit into one of four basic classifications as outlined below (Figure 2.4):

• Roman: perfected by the Greeks and Romans and later modernized in the 18th century, the Roman alphabet displays enormous grace and dignity and is considered by many to be the most elegant typeface family.

• Gothic: this alphabet is the base from which our single-stroke technical lettering has evolved and is the primary style used by the majority of today's designers. It is an easily read and simply executed style that has been in use for many years as a commercial, block-type letter. Its main characteristic is the uniformity in width of all of the strokes. Modifications of this letter include inclined, squared, rounded, boldface, lightface, and serif.

• Script: script alphabets are cursive in nature and resemble handwriting. The lowercase letters are interconnected when used within words or sentence beginnings. Their characteristic free-flowing strokes impart a sense of delicacy and personal temperament and are not considered appropriate for general use in technical drawing.

• Text (Old English): originally used by European monks for recording religious manuscripts, this alphabet is characterized by the use of strokes of different width, due to the original employment of a flat quill pen. This alphabet is rarely used in modern work and is not considered suitable for technical drawing because it is difficult to read and draw.

All of the above typefaces can be produced in italic (which has inclined, lightface, and curved characteristics). The character of the typeface used should always be appropriate to the design being presented. Today there is a large body of well-designed typefaces available in the form of pressure-sensitive dry-transfer sheets in addition to computerized typography.


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Correct spacing of equal areas Incorrect spacing of letter forms

Correct spacing of equal areas Incorrect spacing of letter forms


Figure 2.3 Examples of some of the more popular typefaces used today.



Figure 2.4 Most alphabets currently in use can be classified into four basic categories: Roman, gothic, script and text.

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  • Fatima
    What are the tools use for technical drawing?
    2 years ago
    What are the material use for technical drawing?
    2 years ago
  • ted
    What are building and drawing codes?
    8 months ago
  • pasi
    What are the types of drawing codes in technical drawing?
    7 months ago
  • harrison
    Which is more important building codes or architectural drawings?
    6 months ago
  • adriana udinesi
    What are the building codes for technical drawing?
    5 months ago
  • zahra
    What are drafting materials?
    1 month ago

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