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Engineering Drawing Online Notes , Objective and Interview Questions

An engineering drawing is a type of technical drawing, used to fully and clearly define requirements for engineered items, and is usually created in accordance with standardized conventions for layout, nomenclature, interpretation, appearance 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 drawing, is the most important aspect of mechanical engineering, as it is the fundamental need to develop the design and assembly of a machine. While the interpretation of a component in terms of sketching can be done in various methods, related to Descriptive Geometry, the three most necessary techniques of drawing/projection are:

Orthographic Projection: In this method the object is placed in space in such a way that the front view of it is captured in the vertical plane, and the top view of the same, is captured in the horizontal plane. The projections of the object are perpendicular with the planar screen, and hence, the name ‘orthographic’.

Perspective Projection: This is a simple technique of drawing an object as how one views it. The observer’s eye position, height, and the distance from the object, all influence the outcome of the drawing. Two sub-methods are adopted for this projection technique, namely, Visual Ray Method and Vanishing Point Method.

Isometric Projection: This form of projection gives the total detail of the component under consideration. The basic principle behind isometric projection is that it involves the consideration of three axes that are inclined to each other making equal angles (thus the name since iso- means equal) with each other (120 deg). This is followed by transfer of actual dimensions to the isometric scale involving some basic trigonometric calculations.