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Lecture 3Saturday 10 October 2015 1
ENGINEERING GRAPHICS
1E9Lecture 3: Isometric
Projections
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Lecture 3Saturday 10 October 2015 2
What is ISOMETRIC?
It is a method of producing pictorial viewof an object showing all three faces of theobject simultaneously.
It is a type of parallel projection
It is a type of axonometric projection
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Lecture 3Saturday 10 October 2015 3
Axonometric Projections
Observer at infinity
Projectors parallel to each other and perpendicularto projection plane
Object is inclined with respect to projection plane
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Lecture 3Saturday 10 October 2015 4
Types of AxonometricProjections
Isometric Projection
Dimetric Projection
rimetric Projection
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Lecture 3Saturday 10 October 2015 5
Isometric Projections
!ll angles between axonometric axes aree"ual
he three coordinate axes of the objectappear e"ually foreshortened #about $%&thof true length'
Te !n"#es $et%een !ny t%o of tetree coor&in!te !xes is 1'()
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Lecture 3Saturday 10 October 2015 6
Isometric Termino#o"y
he three coordinate axes are called isometricaxes
!ny line parallel to isometric axesis called
isometric line
! non-isometric line is a line not parallel toany one of the three isometric axis
In isometric projection of cube( the faces of thecube and any plane parallel to them is calledisometric planes
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Lecture 3Saturday 10 October 2015 7
Isometric Sc!#e
rue lengths of the edges of the object aree"ually foreshortened
)orrect isometric projection can be drawn
using an isometric scale #always smallerthan ordinary scale'
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Lecture 3Saturday 10 October 2015 8
Isometric *r!%in"
Isometric Projection*Drawing preparedwith isometric scale onisometric axes
Isometric Drawing*Drawing prepared
with ordinary scaleon isometric axes
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Lecture 3Saturday 10 October 2015 9
Steps+
Step 1Isometric s+etches begin with definingisometric axes( three lines( one verticaland two drawn at $,- from the horiontal.
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Lecture 3Saturday 10 October 2015 10
Steps+
Step 'hree lines of the isometric axes representthe three primary dimensions of theobject* width( height( and depth
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Lecture 3Saturday 10 October 2015 11
Steps+
Step ,Draw the font face of the isometric bloc+.
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Lecture 3Saturday 10 October 2015 12
Steps+
Step -
Draw the rest of the isometric bloc+.
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Lecture 3Saturday 10 October 2015 13
Steps+
Step .
!dd details to the bloc+ starting from thefront face. hen add details to the otherfaces.
S d 10 O b 201 14
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Lecture 3Saturday 10 October 2015 14
Steps+
Step /
Dar+en all visible lines to complete theisometric s+etch. #ma+e sure thatconstruction lines are light'
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Lecture 3Saturday 10 October 2015 15
!xonometric projection shows all $ dimensions( length( widthand height.
he isometric lines are only drawn to scale. Objects
composed entirely of isometric lines can be drawn by ta+ingall measurements parallel to main edges of the enclosing box.
/on0isometric lines are drawn by transferring the ordinates#which are on isometric lines' of the end of the lines
Inclined and obli"ue surfaces are drawn using endcoordinates. 1ox construction and offset measurements arecommon methods
In an isometric drawing( an angle never appears in its truesie. !ngles( irregular curves re"uire special techni"ues
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Lecture 3Saturday 10 October 2015 16
O$jects %it Norm!# S0rf!ces
2a+e an Isometric Drawing with corner !at the bottom
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Lecture 3Saturday 10 October 2015 17
O$jects %it Norm!# S0rf!ces
Lect re 3 Saturday 10 October 2015 18
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Lecture 3Saturday 10 October 2015 18
O$jects %it O$#i0e S0rf!ces
2a+e an Isometric Drawing with corner !at the bottom
NON-ISOMETRIC INE
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Lecture 3Saturday 10 October 2015 19
O$jects %it O$#i0e S0rf!ces
Lecture 3 Saturday 10 October 2015 20
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Lecture 3Saturday 10 October 2015 20
O$jects %it Non2isometric3ines
2a+e an Isometric Drawing with apex !facing front
Lecture 3 Saturday 10 October 2015 21
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Lecture 3Saturday 10 October 2015 21
O$jects %it Non2isometric 3ines
/on0isometric lines are drawn with box constructionand offset measurements
/on0isometric lines are not drawn in true length inisometric drawing #1! is shorter than )! in thisdrawing'
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Lecture 3Saturday 10 October 2015 22
Irre"0#!r O$jects
2a+e an Isometric Drawing of the followingirregular object #pyramid'
Lecture 3 Saturday 10 October 2015 23
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Lecture 3Saturday 10 October 2015 23
Irre"0#!r O$jects
O! and O1 offsets help to locate apex O
)omplete box construction may not beneeded in each case
Lecture 3 Saturday 10 October 2015 24
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Lecture 3Saturday 10 October 2015 24
O$jects %it Circ0#!r Geometry
! circle in a orthographic projection will appear asan ellipse in an isometric drawing.
Instead of actual ellipses often approximate ellipsesare drawn for isometric drawing.
3our0centre ellipses are used to approximate ellipseson isometric planes.
Ho% to &r!% fo0r2centre e##ipse???
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Lecture 3Saturday 10 October 2015 25
Approxim!te E##ipse
Draw the isometric centre lines of the circle. 4sing the
centre lines( draw an isometric s"uare with sides e"ual to thediameter of the circle.3rom the near corners of the box( draw two large arcs withradius 5( using the two red points as centres.Draw the two smaller arcs with radius r( using two green points
as centres.
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Lecture 3Saturday 10 October 2015 26
Cy#in&er
Lecture 3 Saturday 10 October 2015 27
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Lecture 3Saturday 10 October 2015 27
O$jects %it Circ0#!r Geometry
Lecture 3 Saturday 10 October 2015 28
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Lecture 3Saturday 10 October 2015 28
O$jects %it Non2Circ0#!r C0r4e&S0rf!ces
2a+e an Isometric Drawing of the followingcurved object
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ectu e 3 y
O$jects %it Non2Circ0#!r C0r4e& S0rf!ces
! line that appears as a noncircular curve in a normal
orthographic view of an object appears as a non0isometric linein an isometric drawing.
)urves may be drawn using a series of points by measuringalong the normal lines in the orthographic view #offsetmeasurements' and transferring these points on isometric
drawing !ccuracy increases with number of points