Orthographic Projection in Engineering Drawing

Introduction

• Purpose: Produce 2D and 3D drawings of parts or components.
• Projection System: Orthographic projection to show all views (front, side, top, etc.) on 2D planes (X and Y planes).

Quadrant System

• Planes: X (horizontal) and Y (vertical) planes.
• Quadrants: Plane divided into four infinite regions, known as quadrants.
  • Designated anticlockwise from the upper right corner (1st quadrant) to lower right corner (4th quadrant).

Orthographic Projection Rules

• Projection Method: First angle and third angle methods.
• Purpose: Widely used in the design industry.

First Angle Method

• Quadrant Placement: Object placed in the first quadrant.
• Projections:
  • Front View: Projected on the vertical plane.
  • Top View: Projected on the horizontal plane.
  • Left Side View: Projected on a parallel profile plane on the right of the object.
  • Right Side View: Projected on a parallel profile plane on the left of the object.
• Drawing Sheet Arrangement:
  • Front view is on top.
  • Top view is on the bottom.
  • Left-hand side view is on the right of the front view.
  • Right-hand side view is on the left of the front view.

Third Angle Method

• Quadrant Placement: Object placed in the third quadrant.
• Projections:
  • Front View: Projected on the vertical plane between the viewer and the object.
  • Top View: Projected on the horizontal plane.
  • Right Side View: Projected on the right profile plane.
  • Left Side View: Projected on the left profile plane.
• Drawing Sheet Arrangement:
  • Front view is on the bottom of the XY line.
  • Top view is above the XY line.
  • Left-hand side view is on the left of the front view.
  • Right-hand side view is on the right of the front view.

Symbols and Methods

• Symbols: Used to represent first angle and third angle methods.

Reasons for Not Using Second and Fourth Angle Methods

• Overlap Issue: In second and fourth quadrants, views overlap making it impractical.

Conclusion

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