Orthographic 1, Lecture notes of Engineering Drawing and Graphics

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Orthographic Projection

Theory of Projection

Projection - means throw forward

• invented by French scientist Monge in the year 1800

Perspective Isometric Oblique

Pictorial Projection

Methods of Projection

Orthogonal Projection

Oblique Projection

• Projectors are parallel to each other

but not perpendicular to projection

plane

• An oblique projection shows front

and top surfaces that include the

three dimensions of height, width,

and depth.

• The front or principal surface of

an object (the surface toward the

plane of projection) is parallel to the

plane of projection.

• Effective in pictorially representing

objects

45º

60º

Full scale

Full scale

Full scale

Full scale

Half scale

radius = 1

Isometric Oblique

30º 30º

Orthographic (Orthogonal)

The object is at rest

and two coordinate

axes are visible in any

one view

(PP projection plane)

Multiview Projections

The six views

First angle and Third angle projections – BIS Conventions

How to draw plan and elevation?

How to draw end view?

Third Angle Projection

How to draw plan and elevation?

In 3rd angle projection planes are transparent and

objects are viewed through them

First angle projection Vs Third angle projection

Example 1

50

80

25

ᶲ 30

50

All dimensions in mm

Scale 1: