Engr. Faisal Nadeem Saher

PhD Research Scholar, UMP

saher.gis@gmail.com

http://saherfn.weebly.com/notes.html

BAA1112 ENGINEERING DRAWING

ORTHOGRAPHIC

LESSON OUTCOME

After this class, students should be able to do the following:

Understand the principles of first and third angle orthographic projection

Produced a detailed orthographic drawing of a component including all necessary information

ORTHOGRAPHIC PROJECTION

Engineering drawing are normally intended to indicate the shape and size of component or object

All components or objects have three dimensions; ie: length, breadth an depth

The use of technique called orthographic projection is to present the three dimensions object in two dimensions to convey an impression of shape for the component or object

ORTHOGRAPHIC PROJECTIONS

Orthographic Projections are a collection of 2-D drawings that work

together to give an accurate overall representation of an object The views are positioned relative to each other according to either

of two schemes: first-angle or third-angle projection They differ only in the position of the plan, front and side views

Third-angle Projection

First-angle Projection

First and Third Angle Projections

* Note: Only third angle is discussed in this course

First Angle Projection is used in Europe and most of the world. However America and Australia use a method known as Third Angle Projection.

1st and 3rd Angle of Projection

In First Angle Projection we place our object in the First Quadrant (see above figure). This means that the Vertical Plane is behind the object and the Horizontal Plane is underneath the object.

Defining the Six Principal Views or Orthographic

Views

Which Views to Present? Projection of view only needs combination of three

direction of views to complete the object shape; front, plan & side view

View direction is the front view of the object

General Guidelines The view with the biggest area compare to other view. Normally the longest dimension is chosen as the width (or depth) Pick a Front View that is most descriptive of object/the view with most information about the object shape

Glass Box Approach: Designation of third angle views

Place the object in a glass box

Freeze the view from each direction (each of the six sides of the box) and unfold the box

Glass Box Approach: Designation of third angle views

Glass Box Approach: Designation of third angle views

Glass Box Approach: Designation of third angle views

Glass Box Approach: Designation of third angle views

Glass Box Approach: Designation of third angle views

Glass Box Approach: Designation of third angle views

Understanding Section and Cutting Plan

Example of Orthographic Drawing [3rd Angle Projection]

Class Exercise 1 Prepare Orthographic drawing with 3rd Angle of projection using suitable scale.

Class Exercise 2 Prepare Orthographic drawing with 3rd Angle of projection using suitable scale.