1. TA 101: Technical Arts 2015-16 II Dr. Prishati Raychowdhury
Department of Civil Engineering
IIT Kanpur
Office: FB 336; Phone: 6692

2. Orthographic Projections with Dimensions
Lecture 5
Orthographic Projections with Dimensions

3. Review
(a)
(b)
Object in FIRST quadrant
Object in THIRD quadrant

4. Review (a) (b) Third Angle Projection First Angle Projection
RIGHT VIEW
FRONT VIEW
TOP VIEW
Third Angle Projection
First Angle Projection

5. Example: Orthographic Projection

6. Why Projection Method is ImportantF 1 1a 2 2a 3 3a 5 4a 5a 6 6a 7 7a 8a 9a
10a 1a 2a 3a 4a 5a 6a 7a 8a 9a
10a cT bT dT aT eT hT fT gT
450 2 2a 10
10a aR bR hR cR gR fR dR eR

7. Terminology
Convention/Terminology for Civil Engineering /Infrastructure related drawings:
Top view: Plan View (or Plan)
Front view: Front Elevation
Side/Profile view: Side Elevation

8. A typical architectural drawing

11. Dimensioning To describe various features of an object
Size (width, height, depth etc.)
Position of features (e.g. holes) with respect to edges, other holes etc.

12. Purpose of Dimensioning
To make the drawing easier to understand by the manufacturer or builder
Make the drawing simpler, cleaner and more legible
Simpler to draw, redraw or reproduce
Appropriate number of dimensions
Not too many
Not too few

13. Dimensioning Four aspects of dimensioning Unit?
Lines
Symbols
Figures
Notes
R 250
Ø 254, 200 deep
320 95
Unit?
400 thick 95
190
All dimensions in m/cm/mm/FT/inch

14. Dimensioning How many dimensions per view?
The object should be able to be manufactured or built
Most objects: 3 dimensions
Cylinders: 2 dimensions
Sphere: 1 dimension

15. Dimensioning Basics Dimension line should not touch the object
Front view 95
Letter size: 6 mm
Pencil: H
Units not written
Red: Extension line
Blue: Dimension line
Gap between extension line and object: mm
All dimensions in mm

16. Dimensioning Basics Which view to dimension?
Show dimensions in the view that shows the most relevant features
R 250
Ø 254
320 95 95
140
190

17. Dimensioning Basics
A dimension should not be repeated
[e.g. if a dimension is given in the front view, it is not shown again in another view] A D E C B D E

18. Dimensioning Basics
Place dimensions outside the view, as far as possible
R 250
R 250 50 50 25 25 20 20 75 75

19. Dimensioning Basics
Take dimensions out from visible outlines than from hidden lines

20. Dimensioning Basics
Dimensions should be unidirectional as much as possible

21. Dimensioning Basics
Give dimension from Baseline / finished surface / centerline of a hole

22. Dimensioning Basics
Give dimension from Baseline /finished surface /centerline of a hole
Except when centerline (or axis of symmetry) passes through center of hole
Ø 150
2 holes, Ø 50
R 50
R 100
250
500
100 80 30

23. Types of Dimensions
Two types
Size
Location D B B C D E A F

24. Types of Dimensions
Two types
Size
Location P A B C

25. Dimensioning a Length Depending on available space Half Arrows Arrows
2500
250 80 40
Dots
800
160
Lines
500 90
260
190 50

26. Placing of Dimensioning
Only two sides are preferable
Dimensions read from the bottom and from the right

27. Placing of Dimensioning
Arrow and text A A
Dimensions read from the bottom and from the right C C B B D D E E

28. Placing of Dimensioning
Orientation of dimensioning text A A
Dimensions read from the bottom and from the right C C B B D D E E
Unidirectional
Aligned

29. Placing of Dimensioning
Zones for allowed alignments
Leader lines, Arrows, text
Avoid
30-45º
150
120 90
Avoid

30. Placing of Dimensioning
Narrow spaces A A C
Dimensions read from the bottom and from the right C B B D D E E
Unidirectional
Aligned

31. Arrangement of Dimensions
Two basic styles
Parallel Dimensions
Chain Dimensions

32. Arrangement of Dimensions
Combined style

33. Dimensioning Diameters
Most appropriate view
Ensure clarity
Precede with “” to distinguish from length

34. Dimensioning Radii Arcs of circles
Precede with “R” to distinguish from length
R 100
260
R 30
250

35. Dimensioning Dimensioning in limited spaces 6 3 22 19 4.8 5 22 ø26 18
21.5 12
300’ 45”
Dimensioning in limited spaces

36. Example 1: Arrangement of Dimensions

37. Example 2: Over-dimensioning
Do not provide too many dimensions

38. Example 3: Positioning Choose appropriate location J H I Ø G Ø G R 20F B A

39. First Angle Projection

40. ? VIEW
FRONT VIEW
TOP VIEW
SCALE 1:2

41. Next Topic: Isometric Projections
Thank you..
Next Topic: Isometric Projections