An engineering drawing is a technical drawing that shows the shape, structure, dimensions, tolerances, accuracy, and other requirements needed to manufacture a product or part. They are also known as mechanical drawings, manufacturing blueprints, and drawings.
Engineering drawings can be divided into four main categories: General arrangement drawings Detail drawings Assembly drawings Auxiliary views
Here are some types of projections used in engineering drawings: Orthographic projection: A way of representing a 3D object by using several 2D views of the object. The most commonly used views are top, front, and right side. Isometric projection: A method for visually representing three-dimensional objects in two dimensions in technical and engineering drawings. In an isometric drawing, the three axes form 120° angles with each other. Dimensioning: The process of defining the size, form, and location of geometric features and components on an engineering drawing.
A common use is to specify the geometry necessary for the construction of a component and is called a detail drawing. Usually, a number of drawings are necessary to completely specify even a simple component.
These drawings are linked together by a "master drawing." This "master drawing" is more commonly known as an assembly drawing.
The assembly drawing gives the drawing numbers of the subsequent detailed components, quantities required, construction materials and possibly 3D images that can be used to locate individual items.
Although mostly consisting of pictographic representations, abbreviations and symbols are used for brevity and additional textual explanations may also be provided to convey the necessary information.
The process of producing engineering drawings is often referred to as technical drawing or drafting (draughting).
Drawings typically contain multiple views of a component, although additional scratch views may be added of details for further explanation. Only the information that is a requirement is typically specified.
Key information such as dimensions is usually only specified in one place on a drawing, avoiding redundancy and the possibility of inconsistency.
Suitable tolerances are given for critical dimensions to allow the component to be manufactured and function.
More detailed production drawings may be produced based on the information given in an engineering drawing.
Drawings have an information box or title block containing who drew the drawing, who approved it, units of dimensions, meaning of views, the title of the drawing and the drawing number.
Until the 1970s, all engineering drawing was done manually by using pencil and pen on paper or other substrate (e.g., vellum, mylar). Since the advent of computer-aided design (CAD), engineering drawing has been done more and more in the electronic medium with each passing decade. Today most engineering drawing is done with CAD, but pencil and paper have not entirely disappeared.
Some of the tools of manual drafting include pencils, pens and their ink, straightedges, T-squares, French curves, triangles, rulers, protractors, dividers, compasses, scales, erasers, and tacks or push pins. (Slide rules used to number among the supplies, too, but nowadays even manual drafting, when it occurs, benefits from a pocket calculator or its onscreen equivalent.) The tools also include drawing boards (drafting boards) or tables.
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