Unit 5 Multiview Drawings 85 Copyright Goodheart-Willcox Co., Inc. same as those obtained in third-angle projection, but the arrangement on the drawing is different. In essence, the top view is positioned below the front view and a right side view is positioned on the left side of the front view. Figure 5-21 shows a compar- ison between first-angle and third-angle projection for the six principal views of a simple object. In summary, the individual views are the same for both angles of projection. The only dif- ference between the two types is the arrangement of views on the drawing. The ASME and ISO stan- dard symbols to indicate third-angle and first-angle projection are shown in Figure 5-22. The size of the smaller end of the cone should be about the same size as the main lettering on the print. The circular view can be positioned on either side of the trape- zoidal view as long as the orientation of the symbol matches the angle of projection illustrated. One of the two versions of the symbol should be included in the title block for drawings that are read within the international community. Computer-Generated Views In current practice, the views on drawings and prints are often created automatically from 3D models designed with CAD solid modeling soft- ware. There are many benefits to creating views in this manner, including the following: • Ease of construction at any scale, and using either first-angle or third-angle projection. • Ease of updating drawings. As the features of the 3D model change, the drawing views are updated automatically. • Accuracy in representing the geometry. • Intelligent association between the model and the annotations, such as the dimensions, callouts, and thread notes. In Figure 5-23, a front view was created first, and then two additional views were added, as well as a pictorial view to help the print reader visualize the object more easily. The drawing views are linked to the 3D model file. For example, if the size of the threaded hole or the depth of the slot is changed, all of the views update automatically. Goodheart-Willcox Publisher Figure 5-21. The six principal views in third-angle projection compared to first-angle projection. Third-Angle Projection First-Angle Projection Top Top Front Front Right side Right side Left side Left side Rear Rear Bottom Bottom Goodheart-Willcox Publisher Figure 5-22. The type of projection for a drawing is indicated by one of these two symbols appearing in the title block. First-Angle Projection Third-Angle Projection