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Orthographic Projection is a way of drawing an object from different directions. Usually a front, side and plan view are drawn so that a person looking at the drawing can see all the important sides. Orthographic drawings are useful especially when a design has been developed to a stage whereby it is almost ready to manufacture. IMPORTANT: There are two ways of drawing in orthographic - First Angle and Third Angle. They differ only in the position of the plan, front and side views. Below is an example of third angle projection. |
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Opposite is an L-shaped object. In the previous section it was drawn in first angle orthographic projection but below it is drawn using the more popular third angle projection. |
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The position of the three views differs compared to first angle orthographic projection. Look at the first angle projection - what are the main differences ? Study the animation below this may help in working out the differences. |
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THIRD ANGLE PROJECTION |
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Another example of third angle orthographic projection is shown below. Follow the blue, red and green guidelines as the front, side and plan view are constructed. |
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The final arrangement of the views are shown in the drawing below. Notice how the symbol for third angle orthographic projection has been added and the paper has a title block and borderline. |
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Carefully study the symbols shown below. Normally when drawing in first or third angle projection a symbol is drawn which clearly shows which angle of projection has been used. |
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