Engineering Drawing

1. Chapter 9 Dimensioning
 Graphical entities on engineering drawings describe shape and position;
 Dimensions describe the size and location of features of an object.

2. The thick lines used for the figures
The thin ,solid lines used for the dimensions
The extension lines are thin, dark, solid . A gap about 1.5mm out of the object

3. The shape dimensions
45
Φ20
10
43
24
Length, width, height, diameter
width
height
length

4. The position dimensions
55
85
60
15
32
20
12
2×Φ10

5. 45
23
29
18
29
18
45
23
OK
!
NO
!
 The shorter dimensions are nearest to the object outline.
 Dimension lines should not cross extension lines.

6. OK!
NO!
 Dimension should be lined up and grouped together as much as possible.

7. 3.2
1.20.8
 In crowded conditions, gaps may be left in extension lines.

8. 12
36
40 25
12
36
40 25
correct Poor practice
 In general, avoid dimensioning to hidden lines.

9. ￠ 19 ￠ 19 ￠ 19
￠ 19
￠ 19
Too small angle
￠ 19
NO !
CORRECT !

10. If radian< ,not diameter, radius!!!!
0
180
R23.5
R6 R3
R0.5

11. ￠ 19
￠ 19
PREFERED POOR PRACTICE
 Dimensions should not be placed on a view unless doing so
promotes the clearness of the drawing --- placed outside the view.

12.  The vertical dimensions (height) are placed between front and side views.
 The horizontal dimensions (length) are placed between top and front views.
 The width dimensions are placed on top or side views.

13. 28
10
54
20
38
20R34￠ 22
R34
20
38
28
20
54
10
CORRECT NO
 The dimensions should be given where the shapes are shown clearly !!!