Lecture #2
EGR 110 – Engineering Graphics
Reading Assignment: Ch. D in Engineering Graphics Workbook, Series 1.2 or Series 2
Sketching Assignment: Sketching Assignment #2
Chapter D: Orthographic Projection
Last week we concentrated on sketching multi-view drawings when given an
isometric drawing.
This week we will concentrate on sketching isometric drawings when given
multi-view drawings.
Isometric
Multi-view Drawing
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Lecture #2
EGR 110 – Engineering Graphics
Isometric Sketching
• Isometrics are 2D pictorial drawings that give the impression of being 3D.
• Isometrics are primarily intended for visualization.
• Isometrics are often not scaled since the lengths of lines may be unscaled in
order to give the proper 3D impression.
• Isometric sketches use "isometric axes" as shown.
• Isometric graph paper is commonly used to sketch isometrics. Be sure that
the angled lines form 30 angles with the horizontal and not with the vertical
(i.e., the paper can be used only with portrait or landscape orientation, not
both).
O
O
30
30
Isometric Axes
Isometric Graph Paper
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Lecture #2
EGR 110 – Engineering Graphics
Isometric Sketching (continued)
• Note that lines that are parallel in the actual object will still be parallel.
• Remember with circular features to use the "enclosing box" method.
However, the "enclosing box" will be a parallelogram rather than a square
and the hole or circular feature will appear as an ellipse.
Major axis of ellipse
circle
Minor axis of ellipse
“enclosing box”
ellipse
Circle is tangent to the midpoints
of the “enclosing box”
“enclosing parallelogram”
Ellipse is tangent to the midpoints
of the “enclosing parallelogram”
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Lecture #2
EGR 110 – Engineering Graphics
Possible steps in Isometric Sketching
1. Form the "box" which contains the object using construction lines.
2. Look for normal surfaces (parallel to the principle planes of the box). Normal
surfaces are easiest to sketch first. All normal lines will be parallel to one of
the three isometric axes.
3. Fill in additional details (inclined planes, oblique planes, rounded edges, etc.)
4. For holes or rounded features:
a) Locate the "enclosing parallelogram"
b) Sketch the major and minor axes
c) Locate the midpoints for each side of the "enclosing parallelogram"
d) Sketch the ellipse, making sure that it is tangent to each midpoint.
e) The major axis of the ellipse is along the longest diagonal of the
"enclosing parallelogram" and the minor axis is along the shortest
diagonal.
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Lecture #2
EGR 110 – Engineering Graphics
Example: Sketch an isometric drawing for the 3-view layout below (Problem A-5
in Engineering Graphics Workbook, Series 1).
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Lecture #2
EGR 110 – Engineering Graphics
Example: Sketch an isometric drawing for the 3-view layout below (Problem A-7
in Engineering Graphics Workbook, Series 1).
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Lecture #2
EGR 110 – Engineering Graphics
Example: Sketch an isometric drawing for the 3-view layout below.
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Lecture #2
EGR 110 – Engineering Graphics
Example: Sketch an isometric drawing for the 2-view layout below.
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