Unit 2 Vizualizing Shapes 13 Copyright Goodheart-Willcox Co., Inc. To explore third-angle projection further, imagine an object placed in a glass box. Each of the box’s six sides represents a viewing plane. Projectors extend the views from the object to the fl at surfaces of the glass box. This produces six principal views of the object—top, bottom, front, rear, right side, and left side views. In multiview drawings, however, only three primary views are typically used—the top, front, and right side views. Figure 2-2B shows the three primary views projected in the third-angle. Note how the projectors transfer each view to their respective glass surface. On a drawing, the third-angle symbol indicates a third-angle projection, as shown in Figure 2-2C. In Figure 2-3, the surfaces of the box are unfolded to show the six principal views. Visualize, then, the unfolding of the glass box: 1. The front surface remains stationary. 2. The other surfaces hinge and rotate toward the front viewing surface. As the six surfaces are unfolded, the projected views of the top, front, and right side become fl at, like a sheet of drafting paper, as shown in Figure 2-4. First-angle projection is the drawing standard used in many international countries. A drawing viewed and projected from the fi rst quadrant is a fi rst-angle projection. See Figure 2-5A. With fi rst- angle projection, the object is between the viewer and the viewing plane. The viewer transmits the views onto the viewing plane located to the opposite side of the object. See Figure 2-5B. On a drawing, a fi rst-angle symbol indicates a fi rst- angle projection, as shown in Figure 2-5C. Like third-angle projection, the front view is stationary, but the surfaces are unfolded away from the front view and fl attened to show six principal views. See Figure 2-6. Compare Figure 2-4 and Figure 2-6, notice that all the views except for the front view are reversed from each other. The front view is the only common view between the two types of projections. Goodheart-Willcox Publisher The front view surface remains stationary, while the other five view surfaces unfold. Figure 2-3