Engineering Lettering Lettering is an essential element in both traditional drawing and CAD drawing. Graphic communication is often not enough to completely describe an object. Lettered text is often necessary to provide detailed specifications about the drawn object. And there are a number of formal rules that apply to the placement of lettering. Commercial Gothic, also called sans-serif Gothic, is the lettering style of most interest to engineers. It is plain and legible. While admittedly not as beautiful as many other styles, sans-serif letters are comparatively easy to make.
They may be drawn in outline and then filled in. C. W. Reinhardt, formerly chief draftsman for Engineering News, developed alphabets of capital and lowercase inclined and “vertical letters, based on the old Gothic letters. For each letter, he worked out a systematic series of strokes. Reinhardt’s development of single-stroke letters was the first step toward standardization of technical lettering. In 1935, the American National Standards Institute (ANSI) suggested letter forms that are now generally considered as standard. Lettering is freehand drawing and not writing.
Therefore, the six fundamental strokes and their direction for freehand drawing are basic to lettering. The horizontal lines are drawn to the right and all vertical, inclined, and curved strokes are drawn downward. Either vertical or inclined letters may be used, but only one style should appear on any one drawing. Vertical letters are perhaps slightly more legible than inclined letters, but they are more difficult to execute. Both vertical and inclined letters are standard, and the engineer or drafter may be called on to use either. Background areas between letters and words should appear approximately qual, and words should be clearly separated by a space equal to the height of the lettering. Only when special emphasis is necessary should the lettering be underlined. Also, it is not desirable to vary the size of the lettering according to the size of the drawing except when a drawing is to be reduced in reproduction. To meet design or space requirements, letters may be narrower and spaced closer together. In this case, they are called compressed or condensed letters. If the letters are wider than normal, they are referred to as extended letters. Letters also vary as to thickness of the stems or strokes.
Letters having very thin stems are called lightface, while those having heavy stems are called boldface. In any style of lettering, uniformity is essential. Uniformity in height, proportion, inclination, strength of lines, spacing of letters, and spacing of words ensures a pleasing appearance. Uniformity in spacing of letters is a matter of equalizing spaces by eye. The background areas between letters, not the distances between them, should be approximately equal. Space words well apart, but space letters closely within words. Make the spaces between words approximately equal to a capital O.
Uniformity in height and inclination is promoted by the use of light guide lines. As guide in lettering, extremely light horizontal lines are necessary to regulate the height of letters. In addition, light vertical or inclined lines are needed to keep the letters uniformly vertical or inclined. A simple method of spacing horizontal guidelines is to use a scale or bow dividers. Another convenient instrument for drawing guide lines for lettering, dimension figures and section lines is the lettering triangle. Uniformity in strength of lines can only be obtained by the skilled use of properly selected pencils and pens.
Either pencils or pens can be used in lettering. Pencil letters are best made with a medium-soft lead with a conical point or with a suitable thin-lead mechanical pencil. Pencil lettering should be executed with a fairly soft pencil such as an F or H for ordinary paper. The choice of a pen for lettering, in contrast, is determined by the size and style of the letters, the thickness of stroke desired, and the personal preference of the drafter. Good lettering involves artistic design, in which the white and black areas are carefully balanced to produce a pleasing effect.
Letters are designed to look well, and some allowances must be made for errors in perception. If the upper portions of certain letters and numerals are equal in width to the lower portions, the characters appear too-heavy. To correct this, the upper portions are reduced in size where possible, thereby producing the effect of stability and a more pleasing appearance. On working drawings, vertical capital letters are commonly made %” (3. 22 mm) high, with the space between lines of lettering from three fifths to the full height of the letters.
For inclined capital letters, the spacing of horizontal guidelines is the same as for vertical capital lettering. The ANSI-recommended slope of 2 in 5 (or 68. 2’ with horizontal) may be established by drawing a “slope triangle” and drawing the guide lines at random with the T-square and triangle. When large and small capitals are used in combination, the small capitals should be three fifths to two thirds as high as the large capitals. On the other hand, lowercase letters have four horizontal guide lines, called the cap line, waist line, base line and drop line.
Strokes of letters that extend up to the cap line are called ascenders and those that extend down to the drop line, descenders. In spacing horizontal guide lines, the ratio of the distance between the base and waist lines with the distance between the base and cap line may vary from 2:3 or 3:5. The order and direction of strokes and the proportion of inclined lowercase letters are the same as those of vertical lowercase letters. Complete guide lines should be drawn for whole numbers and fractions, especially for beginners.
Fractions are twice the height of the corresponding whole numbers. Make the numerator and the denominator each about three fourths as high as the whole number to allow ample clear space between them and the fraction bar. For dimensioning, the most commonly used height for whole numbers is %” (3. 22 mm), and for fractions %” (6. 4 mm). Today, various forms of press-on lettering and special lettering devices are available. In addition, all computer-aided drafting systems have the capability to produce letters of different heights and styles and to make changes as required.
In whatever way the lettering is applied to the drawing and whatever styles of lettering is used, the lettering must meet the requirements for legibility and microfilm reproduction. It should be remembered that good lettering is always accomplished by conscious effort, though good muscular coordination is of great assistance. There are three necessary aspects of learning to letter –knowledge of the proportions and forms of letters and the order of strokes, knowledge of composition or spacing, and persistent practice with continuous effort to improve. Reference: Giesecke, F. (2001). Technical Drawing. Singapore: Pearson Education Asia.