1. MENG104 ENGINEERING GRAPHICS
ISOMETRIC PROJECTION

2. ISOMETRIC PROJECTION
Isometric drawing is another way of presenting designs/drawings in three dimensions. The example opposite has been drawn with a 30 degree set square. Designs are always drawn at 30 degrees in isometric projection.
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3. Isometric projection is a method for visually representing three- dimensional objects in two dimensions in technical and engineering drawings. It is an axonometric projection in which the three coordinate axes appear equally foreshortened and the angles between any two of them are 120 degrees.
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4. SCALE ADJUSTMENT IN ISOMETRIC VIEWS
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5. HOW TO MAKE AN ISOMETRIC DRAWING
Step 1
If the starting point is not given, begin your drawing about 1” up from the title block and 2/3’s across the page from the left margin
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6. Step 2
From the starting point, draw lines 30 deg. to the left, 30 deg. to the right, and 90 deg. up with light construction lines.
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7. Place the length measurement on the “30 deg. to the left” line,
Step 3
Place the length measurement on the “30 deg. to the left” line,
the thickness measurement on the “30 deg. to the right” line, and
the height measurement on the “90 deg. up” line
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8. Erase excess lines back to each mark.
Step 4
Erase excess lines back to each mark.
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9. Step 5
Draw construction lines 30 deg. to the left and 30 deg. to the right from the height mark.
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10. Draw lines 90 deg. up from both ends
Step 6
Draw lines 90 deg. up from both ends
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11. Erase excess lines back to each intersection.
Step 7
Erase excess lines back to each intersection.
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12. Convert all construction lines to visible lines
Step 8
Draw construction lines 30 deg. to the left and 30 deg. to the right from each end until they intersect.
Convert all construction lines to visible lines
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13. Characteristics of isometric projections
All lines parallel to axes 1, 2 and 3 are isometric lines. 2 3 1
120º
The isometric lines are angled at 30º.
The lines not parallel to axes 1, 2 and 3 are non-isometric lines.
The sides of the cube and all planes parallel to them are isometric planes.
Axes 1, 2 and 3 form 120º angles between one another.
The projection is isometric (equal measures) because the height of axis 1, the length of axis 2 and the width of axis 3 are all proportionally reduced.
Characteristics of isometric projections

14. Sketch from an actual object
STEPS
1. Positioning object.
2. Select isometric axis.
3. Sketch enclosing box.
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.

15. Circle & Arc in Isometric
Four-center method is usually used when drawn an isometric ellipse with drawing instrument.
Sketching Steps
1. Locate the center of an ellipse.
2. Construct an isometric square.
3. Construct a perpendicular bisector from each tangent point.
4. Locate the four centers.
5. Draw the arcs with these centers and tangent to isometric square.

16. How to draw an ellipse composed of four arcs using a compass
1- Trace an isometric square.
2- Find the center of the square using diagonals, then trace the axis lines.
3- Finally, trace the median lines. The meeting point of the medians shows the center of the four arcs of the circle.
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17. Showing circles and arcs of circles in isometrics
Circles and arcs of circles on isometric planes are shown in isometric projection using ellipses within an isometric square.
The sides of the square are equal to the diameter of the circle and each side of the circle touches the square.
To draw a circle in isometric perspective on the computer, use a modified circle inserted into an isometric square.
To draw it as a sketch or with a compass, draw four arcs of the circle in an isometric square.

18. ORTHOGRAPHIC MULTI-VIEW PROJECTION
How to draw an object containing rounded parts
«Construction box»
ORTHOGRAPHIC MULTI-VIEW PROJECTION
ISOMETRIC PROJECTION

19. EXAMPLE 6.1
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20. EXAMPLE 6.2
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21. EXAMPLE 6.3
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