Orthographic, Oblique

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Orthographic, ObliqueIsometric Projections

• Created by
• Carpentry Joinery Section
• Granville TAFE.

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Statement of Objectives

• The student will be able to-
• Reproduce oblique, isometric orthographic
  representations of objects
• Draw the plan view, front and side elevation of a
  particular object given either the isometric or
  oblique representation.
• Draw an isometric or oblique representations of
  an object given the plan, front and side
  elevation.
• State the need for using scales when drawing an
  object.
• Draw the plan of an object at a scale of 12 and
  15
• Find the measurements from a plan when a scale
  is given but no measurements are given on the
  plan.

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Any object can be drawn.

• The purpose of drawing may be to show the object
  either as a picture or to show it in a way that
  would enable someone to make it.

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In the building Trade drawings serve two purposes

1. Cottages can be drawn as a pictorial by an
   architect.
2. Or drawn by a builder to show what it will look
   like when finished.

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In the building Trade drawings serve two purposes
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Housing joints can be shown the same way for
similar reasons.

• Through housing joint

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Cottages can be drawn orthographically

• This shows internal details such as-
• Room sizes and spacing.
• Orthographic projections is from one aspect only.
• This gives the builder the information required
  to do the job.

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Cottages can be drawn orthographically
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This also applies to a simple housing joint for
the same reason
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Pictorial drawings most commonly used in the
building trade are either ISOMETRIC OR OBLIQUE
PROJECTION

• They are probably used more in freehand sketches
  on the job, than detailed drawings.

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Pictorial drawings most commonly used in the
building trade are either ISOMETRIC OR OBLIQUE
PROJECTION
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Isometric projection is a method used to depict
three sides of an object.

• ( ISO meaning equal, metric meaning measure)
• An isometric drawing shows length, width
  thickness.
• However any lines which are not parallel to the
  length, width thickness are not true
  measurements.
• For example the diagonals of a square or
  rectangle are equal on the actual object , but do
  not appear so in isometric.
• The vertical lines are drawn vertically and the
  angle is 30 degrees.

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Isometric projection is a method used to depict
three sides of an object.
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Oblique projection is another method of showing
three sides of an object in one drawing.

• An oblique drawing shows one view in true
  proportion.
• The sides of an object are drawn full size and at
  a angle of 45 degrees.
• To PROPORTION the drawing we halve the
  measurement of the oblique side.

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Oblique projection is another method of showing
three sides of an object in one drawing.
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This can be better illustrated if a cube is drawn
in both isometric oblique projection.

• The diagonals on the face of the oblique drawing
  are equal because this is a true view but not on
  the isometric.

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This can be better illustrated if a cube is drawn
in both isometric oblique projection.
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Orthographic projection is the correct or true
shape of an object drawn on a flat surface.

• It is the main method used to represent an object
  in a drawing.
• It gives three views of the object in three
  separate drawings.
• Gives three basic dimensions, Length, Width
  Thickness
• Gives three views of the object plan, front,
  side elevation

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Orthographic projection is the correct or true
shape of an object drawn on a flat surface.
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The object shown if surrounded by 3 surfaces or
planes (vertical, side vertical horizontal)
each of the 3 views is called projection.

• The three surfaces or planes are to be
  represented on paper as one flat surfaces.

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The object shown if surrounded by 3 surfaces or
planes (vertical, side vertical horizontal)
each of the 3 views is called projection.
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The 3 views of the object on a drawing are
obtained by projecting or throwing points of
the object onto the drawing.

• These projection lines are at 90 degrees to the
  surface of the object. Therefore the view
  obtained will be a true one.

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The plan is obtained by looking down on the
top of the object. (i.e. projecting onto the
horizontal plane.)
The front elevation is projected onto the
vertical plane but looking from the front.
The side elevation is projected onto the side
vertical plane. looking from the side
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Drawing paper represents one flat surface, so if
the objects drawn were laid out flat then the
three views would appear as drawn.

• Projections are made from one view to another.
• Projecting from the plan and front elevation will
  give the side elevation.

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Drawing paper represents one flat surface, so if
the objects drawn were laid out flat then the
three views would appear as drawn.
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Orthographic projection is used for working
drawings it is essential that the sizes or
dimensions are placed onto the drawing.

• Most objects to be drawn are bigger than the
  drawing sheet, then it is necessary to fit or
  scale the object it so it can be placed onto the
  paper.

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Orthographic projection is used for working
drawings it is essential that the sizes or
dimensions are placed onto the drawing.
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To keep the drawing in proportion the actual
dimensions are reduced in the same ratio. This is
called SCALING

• Although the actual measurements are written on
  the drawing they dont actually measure that
  amount on a SCALED drawing.

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To keep the drawing in proportion the actual
dimensions are reduced in the same ratio. This is
called SCALING
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Drawing to scale is the reducing or enlarging by
ratio of an object from its actual size that can
fit onto a working drawing.

• Scaling is a ratio that can be expressed as
  12
  15 110 150 1100
• The scale chosen depends on the size of the
  object and the size of the drawing paper.

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Drawing to scale is the reducing or enlarging by
ratio of an object from its actual size that can
fit onto a working drawing.
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On a scale of 15 the 300 represents 300mm but
to a scale of 15 in represents 60mm
( 300 60 ) 50
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If measurements are indicated on a drawing they
should be used in preference to scaling.

• All dimensions are not shown on a drawing as this
  would clutter the working drawing. If this is the
  case scale matching the drawing can be done but
  accuracy can be compromised.

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If measurements are indicated on a drawing they
should be used in preference to scaling.
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At this stage you should be have some knowledge
of-

1. 3 different types of drawings.
2. How to draw and recognise these types.
3. The purpose of scales.
4. How to use scales.

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Carpenters have to do the actual building which
involves READING plans and interpreting
drawings.Without this knowledge of drawing any
carpenter will find it hard to understand the
plans and therefore hard to build the job.
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