1. Orthographic
Writing

2. TOPICS
Views selection
Alignment of views
Orthographic writing steps
Basic dimensioning
Tangency and intersections

3. View Selection

4. VIEW SELECTION STEPS
1. Orient the object to the best position relative to a glass box.
2. Select the front view.
3. Select adjacent views.

5. STEP 1 : Orient the Object
The object should be placed in its natural position.
The object should present its features in actual size and shape in orthographic views.
GOOD
NO !

6. STEP 2 : Select a Front View
The object’s longest dimension should be presented as a width.
First choice
Second choice
Waste more space
GOOD
Inappropriate

7. STEP 2 : Select a Front View
The adjacent views that are projected from the selected front view should appear in its natural position.
Inappropriate

8. STEP 2 : Select a Front View
Choose the view that have the fewest number of hidden lines.
GOOD
Inappropriate

9. STEP 3 : Select an Adjacent View
Choose the view that have the fewest number of hidden lines.
GOOD
Inappropriate
GOOD
Inappropriate

10. STEP 3 : Select an Adjacent View
Choose the minimum number of views that can represent the major features of the object.
Necessary
Hole’s location can be specified on the same view.
Easy to understand
Difficult to interprete.
Necessary

11. STEP 3 : Select an Adjacent View
Choose the views that are suitable to a drawing space.
POOR
Not enough space
for dimensioning.

12. STEP 3 : Select an Adjacent View
Choose the views that are suitable to a drawing space.
GOOD

13.       Example : View selection mislead to… Size descriptionH W
F.V. H W D
F.V. & T.V.
Three views
F.V. & R.S.V.   
Size description   
Shape description

14. ONE-VIEW DRAWING Flat part having a uniform thickness. Unnecessary
These 2 views provide only information about the part thickness !

15. ONE-VIEW DRAWING Cylindrical-shaped part. Unnecessary Repeat !
Infer from CL
Unnecessary

16. TWO-VIEW DRAWING
There exists an identical view.
Repeat !
Unnecessary

17. TWO-VIEW DRAWING
The 3rd view has no significant contours of the object.
Unnecessary

18. TWO-VIEW DRAWING
The 3rd view has no significant contours of the object.
Unnecessary

19. Alignment of Views

20. ORTHOGRAPHIC VIEWS 1st angle system Right Side View Front View
Top View

21. Orthographic Writing Steps

22. WRITING STEPS
1. Select the necessary views
2. Layout the views.
3. Project the views.
4. Dimension the views.

23. 1. SELECT THE NECESSARY VIEWS
TOP
FRONT

24. 2. LAYOUT THE VIEWS 1:1 A4 Choose an appropriate scale 152 64 25 45

25. PROJECT THE VIEWS

26. DIMENSION THE VIEWS x x z y y x x y y PART NAME NOTES
1. Dimensions in millimeters.
2. ….

27. Basic Dimensioning

28. COMPONENTS 1. Extension lines 2. Dimension lines 3. Leader lines10 27
10 Drill, 2 Holes
R16
2. Dimension lines
3. Leader lines
4. Dimension numbers 17
5. Local notes 43

29. Tangencies and Intersections

30. TANGENT & INTERSECTION

31. TANGENT & INTERSECTION
No line is formed when curved surface tangent to a plane surface.
Line is formed when curved surface intersects a plane surface.
No line
tangent
intersect
No line
tangent
intersect

32. TANGENT & INTERSECTION
limiting element
tangent
tangent
tangent
plane
intersect

33. TANGENT & INTERSECTION
No line
tangent
tangent
tangent
tangent
No line
tangent
No line

34. FILLET AND ROUND
To draw the arc, we must find the location of the center of that arc.
How do we find the center of the arc?

35. To draw an arc of given radius tangent to two perpendicular lines
arc radius r r r

36. To draw an arc of given radius tangent to two perpendicular lines
arc radius r
center of the arc
Starting point
Ending point

37. To draw an arc of given radius tangent to two lines
arc radius r r r + +

38. To draw an arc of given radius tangent to two lines
arc radius r
T.P.1
T.P.2

39. To draw a line tangent to a circle at a point on the circle
Given C

40. To draw a line tangent to a circle from a point outside the circle
Given
mark a tangent point C

41. When circle tangent to other circle
Tangent point R1 C1 R2 C2
R1 + R2
The center of two circles and tangent point lie on the same straight line !!!

42. To draw a circle tangent to two circles I+
Given + C2 + C1
Example

43. To draw a circle tangent to two circles I
Given
Two circles and the radius of the third circle = R + + C2 C1

44. To draw a circle tangent to two circles I
Given
Two circles and the radius of the third circle = R
R + R2
center of the arc
R + R1 R2 C R R1 + + C2 C1
Repeat

45. When circle tangent to other circle
Tangent point R1 R2 C1 C2
R2  R1
The center of two circles and tangent point must lie on the same straight line !!!

46. To draw a circle tangent to two circles II+
Given + C2 + C1
Example

47. To draw a circle tangent to two circles II
Given
Two circles and the radius of the third circle = R + + C2 C1

48. To draw a circle tangent to two circles II
Given
Two circles and the radius of the third circle = R R R2 R1 + +
R – R2 C2 C1
R – R1 C
Repeat

49. To draw a circle tangent to two circles III
Given
Two circles and the radius of the third circle = R R2 R1 + C2 + C1
R + R2
R – R1 C

50. Class Assignment: 01

51. Class Assignment: 02

52. Class Assignment: 03

53. Class Assignment: 04

54. Class Assignment: 05

55. Class Assignment: 06