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Chapter 4Orthographic
Writing
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TOPICS
Views selection
Orthographic writing steps
Alignment of views
Tangency and intersections
Basic dimensioning
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View Selection
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STEP 1 : Orient the Object
The object should be placed in its natural position.
NO !
The object should presents its features in actual
size and shape in orthographic views.
GOOD
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STEP 2 : Select a Front ViewChoose the view that have the fewest number of
hidden lines.
GOOD Inappropriate
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STEP 3 : Select an Adjacent View
GOOD
Inappropriate
Inappropriate
GOOD
Choose the view that have the fewest number of
hidden lines.
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Choose the minimum number of views that can
represent the major features of the object.
STEP 3 : Select an Adjacent View
Necessary
Necessary
Hole’s location can be
specified on the same view.
Difficult to interprete.
Easy to understand
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Choose the views that are suitable to a drawing
space.
STEP 3 : Select an Adjacent View
GOOD
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Example : View selection
Shape description
Size description
F.V.
W D
W
H
Dmislead to…
F.V. & T.V. Three views F.V. & R.S.V.
H
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ONE-VIEW DRAWING
Flat part having a uniform thickness.
Unnecessary These 2 views provide only information
about the part thickness !
1 Thick
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ONE-VIEW DRAWING
Cylindrical-shaped part.
Unnecessary
Repeat !
Infer from CL
Unnecessary
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TWO-VIEW DRAWING
There exists an identical view.
Repeat !
Unnecessary
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The 3rd
view has no significant contours of the object.
TWO-VIEW DRAWING
Unnecessary
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TWO-VIEW DRAWING
Unnecessary
The 3rd
view has no significant contours of the object.
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Alignment of Views
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PROJECTION SYSTEMS
1. First angle system
2. Third angle system
First Quadrant
Third
Quadrant
- European country
- ISO standard
- Canada, USA,
Japan, Thailand
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ORTHOGRAPHIC PROJECTION
1st angle system 3rd angle system
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ORTHOGRAPHIC VIEWS
1st angle system 3rd angle system
Front View
Front View
Right Side View
Right Side View
Top View
Top View
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First angle systemThird angle system
PROJECTION SYMBOLS
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PROJECTION SYMBOLS
d 1.7d
2.2d
Suggested proportion
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Orthographic WritingSteps
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WRITING STEPS
1. Select the necessary views
2. Layout the views.
3. Project the views.
4. Dimension the views.
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1. SELECT THE NECESSARY VIEWS
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DIMENSION THE VIEWS
NOTES
1. Dimensions in millimeters.2. ….
PART NAME
x
x
x x
y
y
y
y
z
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TRANSFERINGTHE DEPTH DIMENSION
2. Use miter line
45
Views too close
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Basic Dimensioning
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1. Extension lines
2. Dimension lines
3. Leader lines
4. Dimension numbers
5. Local notes
COMPONENTS
10 27
43
10 Drill, 2 Holes
R16
1 7
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Tangencies andIntersections
G & S C O
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No line is formed when curved surface tangent
to a plane surface.
No line
No line
TANGENT & INTERSECTION
Line is formed when curved surface intersects
a plane surface.
tangent
tangent
intersect
intersect
TANGENT & INTERSECTION