Post on 24-May-2015
description
Chapter 9 Dimensioning
Graphical entities on engineering drawings describe shape and position;
Dimensions describe the size and location of features of an object.
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
The shape dimensions
45
Φ20
10
43
24
Length, width, height, diameter (radius)
width
height
length
The position dimensions
55
85
60
1532
20
12
2×Φ10
45
23
2918
2918
45
23
OK!
NO!
The shorter dimensions are nearest to the object outline.
Dimension lines should not cross extension lines.
OK!
NO!
Dimension should be lined up and grouped together as much as possible.
3.2
1.20.8
In crowded conditions, gaps may be left in extension lines.
12
36
40 25
12
36
40 25
correct Poor practice
In general, avoid dimensioning to hidden lines.
￠ 19 ￠ 19 ￠ 19
￠ 19
￠ 19
Too small angle
￠ 19
NO !
CORRECT !
If radian< ,not diameter, radius!!!!0180
R23.5
R6 R3
R0.5
￠ 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.
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.
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 !!!