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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 view in the bottom of projected front view.
  • Right side view is projected on the left side of front view. Left plane is unfolded towards left side for right side view.
  • left side view is projected on the right side of front view.
  • Bottom View is projected on top of the front view.

 

Projection Views in 1st Angle ProjectionObject Placement in 1st Angle Projection

 

 

Third Angle Projection  

 

  • In 3rd angle projection, object is placed in third quadrant and the projection plane lies in between the observer and object.
  • 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 view in top of projected front view.
  • Right side view is projected on the right plane and it is placed on right side of front view.
  • Bottom View is projected on the bottom plane and view is placed on bottom of front view

 

 

 

Projection Views in 3rd Angle ProjectionObject Placement in 3rd Angle Projection

 

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