Orthographic drawing

Orthographic drawing

GA and detail drawings are produced by the use of a drawing technique called orthographic projection. This is used to represent 3-D solids on the 2-D surface of a sheet of drawing paper so that all the dimensions are true length and all the surfaces are true shape. To achieve this when surfaces are inclined to the vertical or the horizontal we have to use auxiliary views, but more about these later. Let us keep things simple for the moment.

First angle projection

Figure 2.42a shows a simple component drawn in isometric projection. Figure 2.42b shows the same component as an orthographic drawing. This time we make no attempt to represent the component pictorially. Each view of each face is drawn separately either full size or to the same scale. What is important is how we position the various views as this determines how we `read' the drawing.