Six Principal views

The plane of projection can be oriented to produce an infinite number of views of an object.  However, some views are more important than others.  These principal views are the six mutually perpendicular views that are produced by six mutually perpendicular planes of projection and is shown in figure 12. Imagine suspending an object in a glass box with major surfaces of the object positioned so that they are parallel to the sides of the box, six sides of the box become projection planes, showing the six views – front, top, left, right, bottom and rear.

Object is suspended in a glass box producing six principal views: each view is perpendicular to and aligned with the adjacent views.

Figure 12. Shows the six perpendicular views of an object

The glass box is now slowly unfolded as shown in figure 13. After complete unfolding  of the box on to a single plane, we get the six views of the object in a single plane as shown in figure 14. The top, front and bottom views are all aligned vertically and share the same width dimension where as the rear, left side, front and right side views are all aligned horizontally and share the same height dimension.

Figure 14 shows  the views of the object with their relative positions after the box has been unfolded completely on to a single plane.