chapter 05 pictorial sketching
DESCRIPTION
engineering graphics lectureTRANSCRIPT
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Chapter 5
Pictorial Sketching
ObjectivesBe able to explain the difference between an
axonometric projection and an oblique
projection.
Be able to explain the difference between an
isometric projection and an isometric
drawing/sketch.
Be able to create an isometric and oblique
sketches from an actual object and multiview
drawing.
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AxonometricAxonometric& ObliqueProjection
Axonometric Projection
B
Parallel & normalto picture plane
AB
CD
Lineof
sightA
B
CD
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Axonometric ProjectionType of axonometric drawing
a
1 Isometric All angles are equal
Axonometric axis
a
b c2. Dimetric Two angles are equal.
b c1. Isometric All angles are equal.
AB
CDA
B
D
Axonometric axis
b
a
c3. Trimetric None of angles are
equal.
C
Axonometric axis
Parallel & obliqueto picture plane
Oblique Projection
A
BC
D
Lineof
sight
A
D
C
B
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Oblique Projection
Oblique drawing angle
A
D
C
B
BA
30o45o 60o
Type of Oblique drawing
1) Cavalier 2) CabinetC D
45o 45o
1) Cavalier 2) Cabinet
Fullscale Half
scale
Isometric ProjectionIsometric Projection& Isometric drawing
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Rotate 45about vertical axis
Isometric Projection
Tilt forward (35o16’)
All edges foreshortenabout 0.8 time.
Isometric DrawingIsometric drawing is a drawing drawn on an isometric
axes using full scale.
Isometric projection(True projection)
Isometric drawing(Full scale)
Forshorten
Full scale
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Positions of Isometric AxesIsometric axes can be arbitrarily positioned to create
different views of a single object.
Regularisometric
Reverse axisisometric
Long axisisometric
View point is lookingdown on the top ofthe object.
View point is lookingup on the bottom ofthe object.
View point is lookingfrom the right (or left)of the object.
Distance in Isometric DrawingTrue-length distances are shown along
isometric lines.
Isometric line is the line that run parallel to
any of the isometric axes.
Nonisometric lines
Isometric axes
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IsometricIsometricSketching
1. Place the object in the position which its shape
and features are clearly seen
Sketch from an actual object
2. Define an isometric axis.
3. Sketching the enclosing box.
4. Estimate the size an and relationship of each
and features are clearly seen.
details.
5. Darken all visible lines.
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STEPS
Sketch from an actual object
1. Positioning object.
2. Select isometric axis.
3. Sketch enclosing box.
4. Add details.
5. Darken visible lines.
1. Positioning object.
Sketch from an actual objectSTEPS
2. Select isometric axis.
3. Sketch enclosingbox.
4. Add details.
5 Darken visible lines
Note In isometric sketch/drawing), hidden lines are omitted
unless they are absolutely necessary to completely
describe the object.
5. Darken visible lines.
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1. Interprete the meaning of lines/areas in
Sketch from multiview drawing
multiview drawing.
2. Locate the lines or surfaces relative to isometric
axis.
Top View
Example 1 : Object has only normal surfaces
Front
Top
Regular H
Front View Side View
Side
WD
H
DW
Bottom View
Bottom
FrontSide
Reverse
DW
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Example 2 : Object has inclined surfaces
DH
y
y
x
Nonisometric line
W
x Front View
A x
x
BC
Example 3 : Object has inclined surfaces
A
y
xB
C
x
y
Nonisometric line
ABC
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x
y
Regular
C
Example 4
A
B
B
C D
E
D FFront View
Reverse
A EF
Circle & Arc in IsometricIn isometric drawing, a circle appears as an ellipse.
Sketching Steps
2. Construct an isometric square.
3. Sketch arcs that connect the
tangent points.
Sketching Steps
1. Locate the center of an ellipse.
tangent points.
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Circle & Arc in IsometricFour-center method is usually used when drawn an
isometric ellipse with drawing instrument.
3. Construct a perpendicular
bisector from each tangent point
Sketching Steps
2. Construct an isometric square.
1. Locate the center of an ellipse.
bisector from each tangent point.
4. Locate the four centers.
5. Draw the arcs with these centers
and tangent to isometric square.
Example 5
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Irregular Curve in Isometric
1 Construct points along the
Steps
1. Construct points along the
curve in multiview drawing.
2. Locate these points in the
isometric view.
3 Sketch the connecting lines3. Sketch the connecting lines.
ObliqueObliqueSketching
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Object Orientation Guidelines
Place complex features (arc, hole, irregular shapesurface parallel to frontal plane.
Object Orientation GuidelinesThe longest dimension of an object should beparallel to the frontal plane.
GOOD GOOD
WORSE WORSE
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Object Orientation Guidelines
Which orientation is better ?
Sketch from actual object
D
ESTIMATE DEPTHESTIMATE LINES
45
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Sketch from multiview drawing
Sketch from multiview drawing
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Sketch from multiview drawing
B
C
D
E
AB
Sketch from multiview drawing
B
C
D
E
AB
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Sketch from multiview drawing
B
D
E
C
AB
Sketch from multiview drawing
B
D
E
C
AB