Difference between First Angle Projection vs Third Angle Projection
This is one of the most common topics of discussion in the community of mechanical engineers and designers alike. Beginners who are new to the concept of orthographic drawings often get confused about the two and if you’re one of them, you’re not alone. Ask any professional with hands-on experience of design and tools, he or she will say this is nothing but the means of representing three-dimensional objects in two dimensions. First and third angle projection are nothing but ways of describing what an object looks like from different directions. This is called orthographic projection and orthographic is nothing but engineering drawings or plan views. Now that you understand the concept of orthographic projections, let’s discuss the difference between first and third angle projection.
What is First Angle Projection?
In the first angle projection, the object is placed in the 1st quadrant. The object is positioned at the front of a vertical plane and top of the horizontal plane. First angle projection is widely used in India and European countries. The object is placed between the observer and projection planes. The plane of projection is taken solid in 1st angle projection.
What is Third Angle Projection ?
In the third angle projection, the object is placed in the third quadrant. The object is placed behind the vertical planes and bottom of the horizontal plane. Third angle projection is widely used in the United States. The projection planes come between the object and observer. The plane of projection is taken as transparent in 3rd angle projection.
Difference between First Angle Projection vs Third Angle Projection:
| Sr.no | First Angle Projection | Third Angle Projection |
| 1 | The object is imagined to be in the first quadrant. | The object is imagined to be in third quadrant. |
| 2 | The object lies between the observer and plane of projection. | The plane of projection lies between the observer and object. |
| 3 | The plane of projection is assumed to be non transparent. | The plane of projection is assumed to be transparent. |
| 4 | Front view is at the top of the horizontal axis. | Front view at the bottom of the horizontal axis. |
| 5 | When view are drawn in their relative position Top view comes below Front view, Right side view is drawn to the left side of elevation. | When view are drawn in their relative position Top view comes above Front view, Right side view drawn to the light side of elevation. |
| 6 | A First Angle Projection drawing is identified by the first angle projection symbol. The angle of projection symbol typically appears in angle of projection block near to Title block. | A Third Angle Projection drawing is identified by the third angle projection symbol. The angle of projection symbol typically appears in angle of projection block near to Title block. |
| 7 | It is widely used in Europe, India, Canada. | It is widely used in United State and Australia. |
Summary of First Angle Projection vs Third Angle Projection
Both first angle and third angle projection are the two ways of drawing in orthographic that usually consists of three different views of an object in two dimensions. They are used to obtain engineering drawings for clarity. For the first angle projection the observer is placed on the left side of the object which puts the object right between the plane of projection and the observer. For the third angle projection, the observer is located on the right side of the object which puts the plane of projection exactly between the object and the observer. Although both are graphical methods used in engineering drawings, they differ in the way they position their views.
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