For describing any object completely through its orthographic projections, it is important to select a number of views. The number of views required to describe any object will depend upon the extent of complexity involved in it. The higher the symmetry, the lesser the number of views required.
Some objects with cylindrical, square or hexagonal features or, plates of any size with any number of features in it may be represented by a single view. In such cases, the diameter of the cylinder, the side of the square, the side of the hexagon or the thickness of the plate may be expressed by a note or abbreviation. Square sections are indicated by light crossed diagonal lines. Figure given below shows some objects which may be described by one-view drawings.
Some objects which are symmetrical about two axes may be represented completely by two views Normally, the largest face showing most of the details of the object is selected for drawing the view from the front. The shape of the object then determines whether the second view can be a view from above or a side view.
In general, most of the objects consisting of either a single component or an assembly of a number of components, are described with the help of three views. In such cases, the views normally selected are the views from the front, above and left or right side.