1. Chapter 4
Orthographic
Writing

2. Contents Orthographic writing Additional examples on a view selection
Overall steps
Suggestions on a view selection
Additional examples on a view selection
Alignment of views (Projection systems)
Basic dimensioning
Primary auxiliary view

3. Orthographic writing
Contents

4. Overall steps 1. Select the necessary views
152
1. Select the necessary views 64
Top
25~40
2. Layout the selected views on a drawing sheet. 45
Front
152
Choose a drawing scale
(say 1:1)
3. Complete each selected views. x y z
Top
4. Complete the
dimensions and notes.
Front y y

5. View selection procedures
1. Orient the object to the best position relative to a glass box.
2. Select the front view.
3. Select adjacent views.

6. Suggestions : Orient the object
1. The object should be placed in its natural position.
2. The orthographic views should represent the true size and true shape of an object (as much as possible).
GOOD
NO !

7. Suggestions : Select the front view
1. The longest dimension of an object should be presented as a width (in a front view).
First choice
Inappropriate
Second choice
Good
Use more space

8. Suggestions : Select the front view
2. The adjacent views project from the selected front view should be appeared in a natural position.
Inappropriate

9. Suggestions : Select the front view
3. It has the fewest number of hidden lines.
Good
Inappropriate

10. Suggestions : Select an adjacent view
1. Choose the view that has the fewest number of hidden lines.
Inappropriate
Inappropriate

11. Suggestions : Select an adjacent view
2. Choose the minimum number of views that can represent the major features of the object.
All information is placed
on a single view.
Necessary
Hole’s information is placed on a separated view.
Necessary

12. Suggestions : Select an adjacent view
3. Choose the views that are suitable to a drawing sheet.
Poor
Not enough space
for dimensioning.
Choose another adjacent view.
Good
Change orientation of the
selected views.
Good

13. Summary View selection has 3 steps
Orient
the object
Select
front view
Select
adjacent view
In practice, drafter should consider all recommendations
simultaneously before start to draw.

14. Additional examples on a view selection
Contents

15. Notes Generally, three views orthographic drawing
is selected to describes an object’s information.
In some specific case, a necessary view may be less or more than three views.
Later chapter

16. Object that requires only one-view
Flat (thin) part having a uniform thickness such as a gasket, sheet metal etc.
Cylindrical-shaped part.
Example
1 Thick
Adjacent views provide only a
part’s thickness !

17. Object that requires only one-view
Flat (thin) part having a uniform thickness such as a gasket, sheet metal etc.
Cylindrical-shaped part.
Example
Example
Repeat !
Infer from CL

18. Object that requires only two-view
Identical adjacent view exists.
The 3rd view has no significant contours of the object.
(provides no additional information)
Example
Repeat !

19. Object that requires only two-view
Identical view exists.
The 3rd view has no significant contours of the object.
(provides no additional information)
Example 1

20. Object that requires only two-view
Identical view exists.
The 3rd view has no significant contours of the object.
(provides no additional information)
Example 2

21. Class activity : View selection
Select a necessary view ? 3 2 5 1 6 4

22. Class activity : View selection
Select a necessary view ? 3 2 5 1 6 4

23. Class activity : View selection
Select a necessary view ? 3 2 5 6 1 4

24. Alignment of views
Contents

25. Projection systems 1. First angle system 2. Third angle system
- European countries - ISO standard
First
quadrant
2. Third angle system
- Canada, USA, Japan, Thailand
Transparent
planes
Opaque
planes
Third
quadrant

26. (transparent planes/glass box)
Orthographic views
1st angle system
(Opaque planes)
3rd angle system
(transparent planes/glass box)

27. Orthographic views   1st angle system 3rd angle system Folding line

28. Views arrangement 1st angle system 3rd angle system Top View
Right Side View
Front View
Front View
Right Side View
Top View

29. Projection symbols
1st angle system
3rd angle system d
1.7d
2.2d

30. Basic dimensioning
Contents

31. Dimensioning components10 27
10 Drill, 2 Holes
1. Extension lines
R16
2. Dimension lines
3. Leader lines
4. Dimension numbers 17
5. Local notes 43

32. Primary auxiliary view
Contents

33. Necessity
Auxiliary view is needed when it is desirable to show the true size and shape of a surface that is not parallel to
anyone of the principal planes of projection.
True size can not be observed
from these principal views.

34. Use of auxiliary view
In practice, an auxiliary view is usually a partial view
showing only the desired information.
Example
Complete view
Partial view d d d d

35. Types of an auxiliary view
Primary auxiliary views may be classified into 3 types
by their relative to the principal views.
1. Adjacent to front view
2. Adjacent to top view
3. Adjacent to side view

36. Auxiliary view adjacent to front view
Glass box and revolution
View arrangement
Width
&
Depth
True size
of an inclined plane
Width & Height
&
True length
of edge view
Height
&
Depth

37. Example 1 Do you remember? Depth dimension of the auxiliary view
can be read from top view or side view.
Auxiliary
plane

38. Example 2 Hidden lines of the holes are omitted for clarity. ReferenceB C
Reference
line A D C B A
Start
Prefer
distance

39. Auxiliary view adjacent to top view
Glass box and revolution
View arrangement
True size
of an inclined plane
Width & Depth
&
True length
of edge view
Width
&
Height
Height
&
Depth

40. Auxiliary view adjacent to side view
Glass box and revolution
View arrangement
Width
&
Depth
Height & Depth
&
True length
of edge view
Width
&
Height
True size
of an
inclined plane

41. Example
Start C B
Prefer
distance A
Reference
line A B C