 Welcome to Interpreting Engineering Drawings, Orthographic Projection 1, Third Angle Projection. Technical information about the shape and size of a part is communicated through the use of drawings. Simple parts normally require drawings showing only one view of the part. However, as the shape of a part becomes more complex, a one-view drawing may not be sufficient to explain the size and shape of the part. Orthographic Projection is a drawing method that allows object features to be projected onto an imaginary plane. Let's imagine that this plane is a pane of glass. If we place an object behind the pane of glass, we're able to trace the object's outline by projecting its features onto the glass, which is our imaginary plane. Before we begin drawing, we need to choose our first view. When choosing the front view, select the view that has the best shape or the most contours, shows the most natural position or use, displays the most stable position, provides the longest dimension, and contains the least hidden features. Select the view that best represents the front view. View A is the best choice. Now, let's place the object behind the glass and trace the outline. Move this pane of glass to the side. On the next page, you will place view B behind the pane of glass and trace its outline. This is the projected outline of the side view or profile view of the object. Notice that there is a dashed line in this view. Since the cutout is not visible, a hidden line is placed in the view to show a hidden edge. Let's select view C to trace the top view of the object. We can show all of the features of this object with three views, the front view, the side view, and the top view. To show how orthographic projection works, we will move the panes and place imaginary hinges between them. This method of projecting views onto an imaginary plane is also known as the glass box theory. Add all necessary dimensions, and it's ready for fabrication. Any person working in a manufacturing role will be required to interpret drawings through the use of orthographic projection. This is commonly referred to as blueprint reading. You have completed this learning activity, interpreting engineering drawings, orthographic projection 1, third angle projection.