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.

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.

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.

THIRD ANGLE PROJECTION

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.

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.

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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