SMLease Design

Mechanical Product Design & Development Partner

Blog posts : "engineering drawings"

Why 2nd angle and 4th Angle Projection is not Used

To understand why 2nd and 4th angle projection is not used? First we need to understand the concept of orthographic projection system.

Theoretically there are four projection system, out of which only 1st and 3rd angle projection system are used because of limitation of 2nd and 4th angle projection system.



How Projection System Works

To understand how projection system works We can consider a point in 1st and 3rd

quadrant (ref. image on right)

Consider Point A in 1st quadrant that lies in between observer and projection plane. Front view of point A will be in vertical plane(V.P.) and top view will be on horizontal plane. To get front and top view in 2D plane, as per rule, horizontal plane need to be rotated by 90 degree in clockwise direction. 


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First Angle And Third Angle Projection

Orthographic Projection

Orthographic projection is a method of projection to draw engineering 2D drawings for an object using parallel lines to project different views on to a 2D plane.

Object can be placed in any of four quadrant. First angle and third angle projections are commonly used for making engineering drawing because of the limitation of 2nd and 4th angle projection.


First Angle Projection  


  • In the 1st angle projection, Object is placed in the 1st quadrant and the object lies in between the observer and plane of projection.
  • Front view is projected on vertical plane and top view on horizontal plane.
  • To get drawing views in 2D plane horizontal plane is rotated in clockwise direction, which brings top v…

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