Engineering drawing

Engineering drawing introduction:
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. Its purpose is to accurately and unambiguously capture all the geometric features of a product or a component. The end goal of an engineering drawing is to convey all the required information that will allow a manufacturer to produce that component.
Engineering drawings are often referred to as "blueprints" or "bluelines". However, the terms are rapidly becoming an anachronism, since most copies of engineering drawings that were formerly made using a chemical-printing process that yielded graphics on blue-colored paper or, alternatively, of blue-lines on white paper, have been superseded by more modern reproduction processes that yield black or multicolour lines on white paper.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

Common features of engineering drawings:
Drawings convey the following critical information:
Geometry – the shape of the object; represented as views; how the object will look when it is viewed from various standard directions, such as front, top, side, etc. Dimensions – the size of the object is captured in accepted units. Tolerances – the allowable variations for each dimension. Material – represents what the item is made of. Finish – specifies the surface quality of the item, functional or cosmetic. For example, a mass-marketed product usually requires a much higher surface quality than, say, a component that goes inside industrial machinery. A variety of line styles graphically represent physical objects. Types of lines include the following:
visible – are continuous lines used to depict edges directly visible from a particular angle. hidden – are short-dashed lines that may be used to represent edges that are not directly visible. center – are alternately long- and short-dashed lines that may be used to represent the axes of circular features. cutting plane – are thin, medium-dashed lines, or thick alternately long- and double short-dashed that may be used to define sections for section views. section – are thin lines in a pattern (pattern determined by the material being "cut" or "sectioned") used to indicate surfaces in section views resulting from "cutting." Section lines are commonly referred to as "cross-hatching." Lines can also be classified by a letter classification in which each line is given a letter.
*)Type A lines show the outline of the feature of an object. They are the thickest lines on a drawing and done with a pencil softer than HB.
*)Type B lines are dimension lines and are used for dimensioning, projecting, extending, or leaders. A harder pencil should be used, such as a 2H.
*)Type C lines are used for breaks when the whole object is not shown. They are freehand drawn and only for short breaks. 2H pencil
*)Type D lines are similar to Type C, except they are zigzagged and only for longer breaks. 2H pencil
*)Type E lines indicate hidden outlines of internal features of an object. They are dotted lines. 2H pencil
*)Type F lines are Type F[typo] lines, except they are used for drawings in electrotechnology. 2H pencil
*)Type G lines are used for centre lines. They are dotted lines, but a long line of 10–20mm, then a gap, then a small line of 2mm. 2H pencil
*)Type H lines are the same as Type G, except that every second long line is thicker. They indicate the cutting plane of an object. 2H pencil
*)Type K lines indicate the alternate positions of an object and the line taken by that object. They are drawn with a long line of 10–20mm, then a small gap, then a small line of 2mm, then a gap, then another small line. 2H pencil.
*)The ISO standard considers a projection on the opposite direction, like an X-ray radiography; the top view is under the front view, the right view is at the left of the front view... This is called First Angle Projection.
*)The American standard (called Third Angle Projection) places the left view on the left and the top view on the top.