Basic Drafting Standards And Standardssetting Organizations

In the United States, the American National Standards Institute (ANSI) and the International Organization for Standardization (ISO) have adopted drafting standards that are voluntarily accepted and widely used throughout the world. These standards incorporate and complement other architectural/engineering standards developed and accepted by professional organizations such as the American Institute of Architects (AIA), the American Society of Mechanical Engineers (ASME) and others. Some large firms have adopted their own standards to suit their individual needs.

ANSI Standards for Blueprint Sheets

Most architectural-drafting offices in the United States use ANSI standard sheet sizes as shown in Table 1.1. ANSI Y14.2, Y14.3, and Y14.5 are the standards that are commonly used in the U.S.:

1. In the U.S. letter-size paper is an architectural (first series) A-size sheet. It is 8.5 x 11 inches. An engineer's (second series) A-size sheet is 9 x 12 inches.

2. B-size sheets are double the size of A sheets (11 x 17—also called tabloid—or 12 x 18 inches).

3. C-size sheets are double the size of B sheets (17 x 22 or 18 x 24 inches).

4. D-size sheets are double the size of C sheets (22 x 34 or 24 x 36 inches), and so on.

Table 1.1 ANSI (American National Standards Institute) standard recommended sheet sizes.

U.S. ENGINEERING

DIMENSIONS (inches)

DIMENSIONS (mm)

ANSI A

8.5 ;

11

215.9 >

279.4

ANSI B

11 >

17

279.4 >

< 431.8

ANSI C

17 >

22

431.8 >

558.8

ANSI D

22 >

34

558.8 >

863.6

ANSI E

34 >

44

863.6

< 1117.6

U.S. ARCHITECTURAL

DIMENSIONS (inches)

DIMENSIONS (mm)

ARCH A

9 >

12

228.6 >

304.8

ARCH B

12 >

18

304.8 >

457.2

ARCH C

18 >

24

457.2 >

609.6

ARCH D

24 >

36

609.6 >

< 914.4

ARCH E

36 >

48

914.4 >

< 1219.2

MISCELLANEOUS

DIMENSIONS (inches)

DIMENSIONS (mm)

LETTER

8.5

11

215.9 >

< 279.4

LEGAL

8.5

14

215.9 >

355.6

U.S. GOVERNMENT

8

11

203.2 >

279.4

STATEMENT

5

8.5

139.7 >

< 215.9

ISO Standards

The metric drawing sizes correspond to international paper sizes, in Europe and many other countries ISO (International Standards Organization) metric measurements are used (Table 1.1). The ISO defines a set of standard metric line widths for drafting. For example, the ISO A series of sheet sizes is based on a constant width to length ratio of 1: V2. Thus, each smaller sheet size is exactly half the area of the previous size, so that if we cut an A0 sheet in half, we get two A1 sheets; if we cut an A1 sheet in half, we get two A2 sheets; and so on. In Figure 1.2 the A0 size is defined as having an area of 1 square meter. This lets us express paper weights in grams per square meter.

The relationship of 1: V2 is particularly important for reduction onto microfilm or reduction and enlargement on photocopiers. Metric equipment including microfilm cameras, microfilm printers, photocopiers, as well as drawing pen sizes are designed around this ratio. This simplifies the process of archiving drawings, resizing, and modifying drawings.

Like the ISO A-series sheet sizes, the pen sizes increase by a factor of two, which allows additions and corrections to be made on enlargements or reductions of drawings. Each width is assigned a color code. The color code corresponds to that for the matching lettering stencil. Line widths and color codes are standardized across all manufacturers.

Other Standard-Setting Organizations

As previously mentioned, ANSI and ISO are the two main drafting-standard-setting bodies. However, there are other organizations that have developed engineering standards that complement these. Like

Page Print Sizes
Figure 1.4 Diagram showing ISO (International Standards Organization) metric sheet sizes.

the ANSI, the American Society of Mechanical Engineers (ASME) has standardized drawing-sheet sizes that are designated by letter and published in MIL-STD-100A. ASME also published the ASME Y14.5M-1994 Dimensioning and Tolerancing standard. Other standard-setting organizations include the American Institute of Architects (AIA), the Canadian Standards Association (CSA), the American Welding Society (AWS), and others. Moreover, some large firms have adopted their own standards to suit their individual needs. In the final analysis, the drawing-sheet sizes you use are determined by the needs of your employer or client and your need to economically lay out required information.

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