What Are Third Angle Orthographic Drawings?

Third angle orthographic drawings are two dimensional drawings of objects typically used for the development of manufactured products. The drawings are completed for various angles.

As working drawings, orthographic drawings or projections are usually completed of the front view, side view and plan view of the given object. The plan view encompasses the whole object from above. Third angle orthographic projections are one of two conventions for these types of drawings. First angle projection is usually used in Europe, while third angle projections are used in Australia and America.

In third angle orthographic drawings, the object is placed in what is called the third quadrant. This means that the vertical plane is in front of the object and the horizontal plane is above it. This is in contrast to first angle orthographic drawings or projections, which place the object in front of the vertical plane and above the horizontal plane.

Orthographic working drawings are usually produced when an object or product is nearly ready for manufacture and are used by engineers in designing the manufacturing details and actual process. Because the differences between first angle and third angle drawings are minimal, most engineers are able to interpret and use both types in practice.