ED-1 Course - Drawing Sizes

Understanding an electrical drawing (did you know?): Drawings sizes 

1- single-sheet Drawings
There have been many standard sizes of paper at different times and in different countries, but today the two widespread systems in use is the international standard (A4 and its siblings) and ANSI system.

A- The international standard: ISO 216
The international paper size standard, ISO 216, is based on the German DIN 476 standard for paper sizes. ISO paper sizes are all based on a single aspect ratio of square root of 2, or approximately 1:1.4142. as in fig.1


The base A0 size of paper is defined to have an area of one m². With the given aspect ratio of square root of two, this corresponds to a piece of paper which its longer side is one metre multiplied by the square root of the square root (that is, the fourth root) of two and the shorter side being the inverse of this value. Rounded to millimetres the A0 paper size is 841 by 1,189 millimetres (33.1 × 46.8 in).

Successive paper sizes in the series A1, A2, A3, and so forth, are defined by halving the preceding paper size along the larger dimension. The most frequently used paper size is A4 (210 × 297 mm). see fig.2


The main advantage of this system is its scaling: if a sheet with an aspect ratio of √2 is divided into two equal halves parallel to its shortest sides, then the halves will again have an aspect ratio of √2. Folded brochures of any size can be made by using sheets of the next larger size, e.g. A4 sheets are folded to make A5 brochures. The system allows scaling without compromising the aspect ratio from one size to another—as provided by office photocopiers, e.g. enlarging A4 to A3 or reducing A3 to A4. Similarly, two sheets of A4 can be scaled down and fit exactly 1 sheet without any cutoff or margins. 

B- ANSI paper sizes
In 1996, the American National Standards Institute adopted ANSI/ASME Y14.1 which defined a regular series of paper sizes based upon the de facto standard 8+1⁄2 × 11 in (215.9 × 279.4 mm) "letter" size which it assigned "ANSI A". This series also includes "ledger"/"tabloid" as "ANSI B". see fig.3


This series is somewhat similar to the ISO standard in that cutting a sheet in half would produce two sheets of the next smaller size. Unlike the ISO standard, however, the arbitrary aspect ratio forces this series to have two alternating aspect ratios. The ANSI series is shown below.

With care, documents can be prepared so that the text and images fit on either ANSI or their equivalent ISO sheets at 1:1 reproduction scale.

Other, larger sizes continuing the alphabetic series illustrated above exist, but it should be noted that they are not part of the series per se, because they do not exhibit the same aspect ratios. For example, Engineering F size (28 × 40 in or 711.2 × 1,016.0 mm) also exists, but is rarely encountered, as are G, H, ... N size drawings. G size is 22+1⁄2 in (571.5 mm) high, but variable width up to 90 in (2,286 mm) in increments of 8+1⁄2 in (215.9 mm), i.e., roll format. H and larger letter sizes are also roll formats. see fig.4


2- Multi-sheet Drawings
Multi-sheet drawings are permitted in all sizes.

The first sheet of a Multi-sheet drawing shall always contain the complete Title block, List of Material, Revision Block, and general notes.

All sheets of Multi-sheet drawings shall be of the same letter size. Use of Multi-sheet drawings shall be found to be advantageous for certain types of schematics and diagrams.

Sheet numbering for all first sheets shall include the total number of sheets, as “SHEET 1 OF 1,” “SHEET 1 OF 2,” etc. Numbering of continuation sheets shall be limited to stating the specific sheet number (e.g., “SHEET 2,” “SHEET 3”) without specifying the total number of sheets.

1 comment: