Principle of orthographic projection First and third angle projection

1. P R E S E N T E D B Y M R . D . H A L L
Orthographic Projection

2. Orthographic projection
 Orthographic projection is the most common method
employed in engineering to produce the drawings
giving details from which components are made.

3. Types of Orthographic projections
Two angles are used in ORTHOGRAPHIC
projections. These are known as FIRST ANGLE
projection and THIRD ANGLE projection.
 1st Angle projection – commonly used through out
Europe and the rest of the world.
 3rd Angle projection- commonly used in the USA.

4. Types of Orthographic projections
 In either First Angle or third Angle orthographic
projection, the object which is to be drawn is placed
in one of the angles formed by a vertical plane
crossing a horizontal plane.

5. Planes
A plane can be regarded as a flat surface. Orthographic
projection depends upon the projection of views on to
planes.
Vertical Plane
Horizontal Plane

6. Meaning of Orthographic
 If two planes meet at right angles to each other they
are said to be “orthogonal “. The word orthographic
is made up from the two words orthogonal and
graphical. The word graphical refers to the drawings
necessary for producing orthographic projections.

7. Angles formed by Vertical and Horizontal planes
Look in this direction to see plan
Lookinthisdirectiontoseefrontview

8. Front View
 The object is then viewed looking at its front and
what is seen is projected onto the vertical plane. The
resulting drawing is called the “front view”.

9. Plan
The object is also viewed from above and what is
seen is projected onto the horizontal plane. This
drawing is called a “plan”.

10. Intersection of Vertical and Horizontal planes
2nd Angle
(not used)
First
Angle
Third
Angle
4th Angle
(not used)
Look in this direction to see plan
Lookinthisdirectiontoseefrontview
(b) Vertical and horizontal planes as seen from
arrow A
(a) Pictorial view of Planes

11. First Angle
Vertical Plane
Horizontal Plane
The vertical plane (VP)
and horizontal plane (HP)
are shown in their First
Angle position. The two
planes are at right angles
to each other.

12. Object placed in 1st Angle
Front
view
Plan

13. Front view and Plan projected to VP and HP in 1st
angle
Front view
Plan
Plan
Front view
The resulting front
view on the VP and
the Plan on the HP
projected in the
direction of the
viewing

14. 1st Angle projection
Two plane swung to lie in the
same flat surface showing
the front elevation(view) and
plan.

15. Two views 1st Angle projection
The resulting First Angle
orthographic drawing giving
two views of the OBJECT.

16. Three views 1st angle projection
Steps in obtaining three view Orthographic
projection

17. Three views 1st angle projection
The object placed in position in the
right angle formed by the two
Vertical Planes and Horizontal
Plane.

18. Three views 1st angle projection
The resulting Three Views
projected in the direction of
the viewing

19. Three views 1st angle projection
Three plane swung to
lie in the same flat
surface

20. Three views 1st angle projection
The resulting First
Angle orthographic
drawing giving the three
views of the OBJECT

21. Three views 1st angle projection
 The line joining the two VPs and HP are not shown.
 The PLAN lies exactly below the FRONT VIEW. The
PLAN is in -line with the FRONT view.
 The END view is exactly on the right-side or left- side
of the FRONT view. The END view is in-line with the
front view.
 The END view on the right of the Front view is the
view seen from the left of the front view.
 The British Standard symbol for 1st Angle is
included.

22. Multi-view 1st angle projection
END view looking from
the right side of the
object

23. Multi-view 1ST ANGLE PROJECTION
The resulting First
Angle orthographic
drawing with the
END view looking
from the right side of
the front view.

24. Multi-view 1st angle orthographic
projection
END view looking
from the left side of
the object

25. Multi-view 1st angle orthographic projection
The resulting First
Angle orthographic
drawing with the
END view looking
from the left side of
the front view.

26. Four view orthographic projection
LOOK IN THIS
DIRECTION TO SEE
END VIEW 1
LOOK IN THIS
DIRECTION TO SEE
END VIEW 2
LOOK IN THIS
DIRECTION TO SEE
FRONT VIEW
LOOK IN THIS
DIRECTION TO SEE
PLAN

27. Four views placed in 1st angle

28. Third Angle Orthographic Projection
3rd
Angle
3rd
Angle

29. Third Angle Projection (VP and HP)
The vertical plane (VP)
and horizontal plane (HP)
are shown in their Third
Angle position. The two
planes are at right angles
to each other.

30. HP swung to lie in same plane as VP
To form a two
dimensional surface,
it is imagined that
the HP is swung to
lie in the same plane
as the VP-as if the
two planes were
hinged together.

31. Isometric view of part of a Jig Clamp
A pictorial drawing
of the part of JIG
CLAMP.

32. Object Placed in 3rd Angle
PLAN
FRONT VIEW
The Jig Clamp is
placed in position in
the right angle
formed by the VP
and HP. The two
direction of viewing
are shown by
arrows

33. Front view and Plan projected on the VP and HP
The resulting front
view on the VP and
plan on the HP
projected in the
direct direction of
viewing

34. Front view and Plan projected on the VP and HP
The two
planes
swung to lie
in the same
flat surface

35. Front view and Plan spaced on a drawing

36. 3rd Angle Three View Projection
A second VP
is added to
the VP and
HP in their
3rd Angle
position

37. Placing the three planes into a two-dimensional
flat surface
1st Stage
The second
VP is swung
through a
right angle to
lie in the
same
surface as
the first VP.

38. Placing the three planes into a two-dimensional
flat surface
2nd Stage
HP is swung
through a
right angle to
lie in the
same
surface as
the first VP.

39. Object placed in third angle
The Object is
placed in the
angles formed by
the two VPs and
the HP. The three
directions of
viewing to obtain a
front view, an end
view and a plan
are shown by
arrows
Front View
Plan
Left side
End View

40. Front view, end view and plan projected from
direction of viewing
Resulting front
view and end view
on the two VPs
and plan on the
HP resulting from
projecting from the
three directions
viewing.

41. Three views 3rd Angle projection
The three planes
carrying the three
views swung so as
to lie in the same
flat surface

42. Third Angle Orthographic Projection
Third Angle
Orthographic
drawing giving the
three views of the
JIG CLAMP.

43. Object placed in third angle
Right side
End View
Front View
Left side
End View
Plan

44. 4 View 3rd Angle Projection

45. 3rd Angle Projection
 The Plan lies exactly above the Front View. The Plan
is inline with the Front view
 The End view on the left of the Front view is the view
seen as viewed from the left of the Front view. The
End view is in-line with the Front view.
 The British Standard Symbol for 3rd Angle projection
is included.

46. THE PROJECTION SYMBOL (SIGN)
The pictorial view of the
frustum of a cone is
shown. The front view
and end view of the
frustum is used to
develop the orthographic
projection symbol.

47. THE PROJECTION SYMBOL (SIGN)
The frustum is placed in
the 1st Angle position.

48. THE PROJECTION SYMBOL (SIGN)
The resulting Front
view and End view of
the frustum of the
cone drawn in 1st
Angle projection.

49. 1st ANGLE PROJECTION SYMBOL (SIGN)

50. THIRD ANGLE PROJECTION SYMBOL (SIGN)

51. CONSTRUCTION OF PROJECTION SYMBOL

52. Machine part