First Angle and Third Angle Projection

Understanding 1st and 3rd angle projection, requires knowledge of Orthographic projection. In this article, first we will understand, what is orthographic projection? Afterwords we will understand, how to draw a projection view using 1st and 3rd angle projection.

What is Orthographic Projection ?

Most engineers use orthographic projection method to draw 2D engineering drawings.

Orthographic projection uses parallel lines, to project different views on to a 2D plane.

Objects are placed only in 1st or 3rd quadrant due to limitation of 2nd and 4th quadrant projection system.

First Angle Projection  

In the 1st angle projection, object lies in 1st quadrant and in between observer and plane of projection.

To draw drawing  views, Front view is projected on vertical plane and top view on horizontal plane.  

To draw views on 2D plane, horizontal plane is rotated in clockwise direction. This rotation brings top view in the bottom of projected front view.

Right side view is projected on vertical left plane. While left side view is projected on vertical right plane.

To draw right side view on 2D plane, left plane is unfolded towards left side. As a result, Right Side View is projected on left side of front view.

Similarly Left side view is projected on the right side of front view.

3rd Angle Projection 

In 3rd angle projection, object lies in third quadrant and the projection plane lies in between the observer and object.

For drawing views, Front View is projected on vertical plane and top view on horizontal plane.

To draw views in 2D plane, horizontal plane is rotated in clockwise direction. This rotation brings top view in top of projected front view.

In the same way, we projected views in first angle projection.

Right side view is projected on vertical right plane. While left side view is projected on vertical left plane.

To draw right side view on 2D plane, Right plane is unfolded towards right side, As a result, Right side view is projected on right side of front view.

Similarly left side view id projected on left side of front view. 

Bottom View is projected on the bottom plane and view is placed on bottom of front view

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