Engineering Drawing: First angle projection and Third Angle Projection

Engineering Drawing is the language of Engineers. Having a good communication skill is one important qualities for a successful career. If you want yourself to be a Successful Engineer sound knowledge in Engineering Drawing is a Must.

Al though there are various important things to learn in Engineering drawing we will first learn to understand the difference between the First angle projection and Third angle projection. In later posts we can learn more on this.

Projection refers to the view of the object on a plane. The Design Engineer who imagines a object does it in the form of 3D. However while presenting his imagination to a manufacturing engineer he needs to present it in the form of 2D. Since 3D drawing on a paper will not be able to show all the details of the Object.

Technically the 3D drawings are identifies as Isometric Drawings and the 2D Drawings are Identifies as Orthographic Drawings.

To ensure complete details of the 3D object is communicated, the 2D drawing has many views such as Front View, Top View, Bottom View, Right Hand Side  View, Left hand Side View etc.

To have a standard method in preparing the 2D drawings on a paper the Views are drawn using two methods, they are First Angle Projection and Third Angle Projection

The angle of projection is identified based on the quadrant the object that is placed for projection of Views.

First Angle projection

If the object is placed in the First Quadrant for viewing the projections, the angle of projection is identified as First angle Projection. In First angle projection the Object is placed in between the Viewer and the Plan.

In simple terms if the Order is Viewer – Object – Plan is First Angle Projection.

First Angle projection

In the above image we can see that the Object is placed in between the Viewer and the Plan.

The Standard symbol to represent First Angle Projection is

First Angle Projection

Third Angle Projection

If the object is placed in the Third Quadrant for viewing the projections, the angle of projection is identified as Third angle Projection. In Third angle projection the Plan is placed in between the Object and the Viewer.

In simple terms if the Order is Viewer – Plan – Object is Third Angle Projection.

Third Angle projection

In the above image we can see that the Plan is placed in between the Viewer and the Object.

The Standard symbol to represent Third Angle Projection is

Third Angle Projection

I hope this post would have helped you in understanding the differences between the First Angle Projection and Third Angle Projection. Leave your comments below on what was your key learning from this post. Also write to us if you have any questions further.

There are some very good books to read on this topic, however here are below few highly recommended books which are simple and clear to understand.

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