- The Nominal Size of lettering is defined by the height (h) of the outline contour of the upper-case (capital).
- Central Line is the imaginary line in the middle of each line or line element which is a constitutive part of a graphic character set.
- If we consider d as the width of the line element and h as the height of the line element, then the two standard ratios for d/h are: 1/14 and 1/10, which are feasible because they result in a minimum number of line thicknesses.
- Location of Central Lines- The nominal size (h) and the spacing between characters (a) shall be taken as the basis for defining the central line.
- Range of Nominal Sizes -The range of nominal sizes are 2.5 mm ;3.5mm ; 5 mm; 7 mm; 10 mm; 14 mm; 20 mm;
- The multiple of 1.414(square root of 2) is the range of heights for lettering is derived from the standardized progression of dimensions for paper sizes.
- Lettering Angle-The lettering may be vertical (upright) or inclined (sloped) to the right at 75° from the horizontal.
- The spacing between two characters may be reduced by half, if this gives a better visual effect.
- various letters are divided into no. of parts so that dimensions will be accurate.
- The size of letter is described by its height. According to the height of letters, they are classified as :
Lettering A
| Characteristic | Parameter | Ratio | Dimensions(mm) | ||||||
|---|---|---|---|---|---|---|---|---|---|
| Lettering Height (Height of capitals) | h | (14/14)h | 2.5 | 3.5 | 5 | 7 | 10 | 14 | 20 |
| Height of lower case letters (without stem or tail) | c | (10/14)h | - | 2.5 | 3.5 | 5 | 7 | 10 | 14 |
| Spacing between characters | a | (2/14)h | 0.35 | 0.5 | 0.7 | 1 | 1.4 | 2 | 2.8 |
| Minimum spacing of base characters | b | (20/14)h | 3.5 | 5 | 7 | 10 | 14 | 20 | 28 |
| Minimum spacing between words | e | (6/14)h | 1.05 | 1.5 | 2.1 | 3 | 4.2 | 6 | 8.4 |
| Thickness of lines | d | (1/14)h | 0.18 | 0.25 | 0.35 | 0.5 | 0.7 | 1 | 1.4 |
Lettering B
| Characteristic | Parameter | Ratio | Dimensions(mm) | ||||||
|---|---|---|---|---|---|---|---|---|---|
| Lettering Height (Height of capitals) | h | (10/10)h | 2.5 | 3.5 | 5 | 7 | 10 | 14 | 20 |
| Height of lower case letters (without stem or tail) | c | (7/10)h | - | 2.5 | 3.5 | 5 | 7 | 10 | 14 |
| Spacing between characters | a | (2/10)h | 0.5 | 0.7 | 1 | 1.4 | 2 | 2.8 | 4 |
| Minimum spacing of base characters | b | (14/10)h | 3.5 | 5 | 7 | 10 | 14 | 20 | 28 |
| Minimum spacing between words | e | (6/10)h | 1.5 | 2.1 | 3 | 4.2 | 6 | 8.4 | 12 |
| Thickness of lines | d | (1/10)h | 0.25 | 0.35 | 0.5 | 0.7 | 1 | 1.4 | 2 |