Lecture 5 Tuesday 18 April 2023 1

ENGINEERING GRAPHICS1E7

Lecture 5: Isometric Projections

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Isometric Terminology

• The three coordinate axes are called isometric axes

• Any line parallel to isometric axes is called isometric line

• A  non-isometric line is a line not parallel   to   any   one   of   the three isometric axis

• In isometric projection of cube, the faces of the cube and any plane parallel to them is called isometric planes

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Notes

• Objects composed entirely of isometric lines can be drawn by taking all measurements parallel to main edges of the enclosing box.

• In  an  isometric  drawing,  an angle never appears in its true size.

• Non-isometric lines are drawn by transferring the ordinates (which are on isometric lines) of the end of the lines

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Objects with Normal Surfaces

Make an Isometric Drawing with corner A at the bottom

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Objects with Normal Surfaces

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Objects with Oblique Surfaces

• Make an Isometric Drawing with corner A at the bottom

NON-ISOMETRIC LINE

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Objects with Oblique Surfaces

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Objects with Non-isometric Lines

• Make an Isometric Drawing with apex A facing front

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Objects with Non-isometric Lines

• Non-isometric lines are drawn with box construction and offset measurements

• Non-isometric lines are not drawn in true length in isometric drawing (BA is shorter than CA in this drawing)

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Irregular Objects

• Make an Isometric Drawing of the following irregular object (pyramid)

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Irregular Objects

• OA and OB offsets help to locate apex O

• Complete box construction may not be needed in each case

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Notes

• Axonometric projection shows all 3 dimensions, length, width and height

• The isometric lines are only drawn to scale.

• Inclined and oblique surfaces are drawn using end coordinates

• Angles, irregular curves require special techniques

• Box construction and offset measurements are common methods