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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

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TANGENT & INTERSECTION

intersect

tangent

tangenttangent

plane

limiting element