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Engineering drawing

An engineering drawing is a type of drawing that is technical in nature, used to fully and clearly define requirements for engineered items, and is usually created in accordance with standardized conventions for layout, nomenclature, interpretation, appearance (such as typefaces and line styles), size, etc.

Engineering drawings are often referred to as "blueprints." However, the term is an anachronism, and is due to the fact that most copies of engineering drawings were formerly made using a chemical printing process that yielded graphics on blue-colored paper.

The process of producing engineering drawings, and the skill of producing them, is often referred to as technical drawing, although technical drawings are also required for disciplines that would not ordinarily be thought of as parts of engineering.

Table of contents
1 Common features of engineering drawings
2 Multiple views and projections
3 Showing Dimensions
4 Notes
5 Sizes of Drawings

Common features of engineering drawings

A variety of line styles are used to graphically represent physical objects. Types of lines include the following:

Here is an example of an engineering drawing. The different linetypes are colored for clarity.
Black = object line and hatching
Red = hidden line
Blue = center line
Magenta = phantom line or cutting plane

Multiple views and projections

In most cases, a single view is not sufficient to show all necessary features, and several views are used. Types of views include the following:

Showing Dimensions

The required sizes of features are conveyed through use of dimensions. Distances may be indicated with either of two standardized forms of dimension: linear and ordinate.

Sizes of circular features are indicated using either diametral or radial dimensions. Radial dimensions use an "R" followed by the value for the radius; Diametral dimensions use a circle with forward-leaning diagonal line through it, called the diameter symbol, followed by the value for the diameter. A radially-aligned line with arrowhead pointing to the circular feature, called a leader, is used in conjunction with both diametral and radial dimensions. All types of dimensions are typically composed of two parts: the nominal value, which is the "ideal" size of the feature, and the tolerance, which specifies the amount that the value may vary above and below the nominal.


Notes--textual information--are also typically included in drawings, specifying details not otherwise conveyed. Notes are almost always in completely uppercase characters, for uniformity and maximal legibility after duplication of the drawing, which may involve substantial reduction in size. Leaders may be used in conjunction with notes in order to point to a particular feature or object that the note concerns.

Sizes of Drawings

Sizes of drawings typically comply with either of two different standards, metric or U.S. customary, according to the following tables:

Metric Drawing Sizes (mm)
A4210 X 297
A3297 X 420
A2420 X 594
A1594 X 841
A0841 X 1189

U.S. Customary Drawing Sizes
A8.5" X 11"
B11" X 17"
C17" X 22"
D22" X 34"
E34" X 44"

The metric drawing sizes correspond to international paper sizes. The U.S. customary "A-size" corresponds to "letter" size, and "B-size" corresponds to "ledger" size.

ANSI Y14.2, Y14.3, and Y14.5 are standards that are commonly used in the U.S.

See also: