This document provides information about isometric and orthographic projections used in engineering drawings. It includes examples of isometric views of objects and their corresponding orthographic projections. Key points covered include: - Isometric projection shows a 3D object with length, breadth and height represented at 30 degree angles. Hidden lines are shown with dashed lines. - Orthographic projection uses front, top and side views. The first angle projection places the front view on the left and other views arranged around it. The third angle projection places views in the opposite arrangement. - Exercises are provided to identify hidden and visible lines/planes in examples and understand the relationship between corresponding points in orthographic views.

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2. ENGINEERING DRAWING N2
ISOMETRIC PROJECTION
ORTHOGRAPHIC PROJECTION
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3. 1. Isometric Projection
Isometric Projection is the three dimensional
drawing of an object. The length, breadth and
height of the object are represented in three
directions as shown in Figure 1 below.
Taking point A as reference point, the line AF
is at an angle 30 0 measuring anti- clockwise
from the positive x axis.
Similarly, the edges or lines AD and AB are at
90 degrees and 150 degrees from the positive
x axis respectively. Careful observation should
be given to the fact that all edges or lines are
parallel to any one of these lines (AF, AD &
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4. -X 30 0
90 0
30 0 X
B
C
A
D
E
F
Y
A
B
C
D
E
F
G
H
H
Fig 1 Fig 2
A
H
Fig 3
J
D
Fig 4
N
E
B
C
D
G
E
F
H
I
J
K
L
M
O
Q
A
B
C
I
G
F
H
G
Right Hand ViewLeft Hand View
Top View
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5. -X 30 0
90 0
30 0 X
B
C
A
D
E
F
Y
A
B
C
D
E
F
G
H
H
Fig 1 Fig 2
A
H
Fig 3
J
D
Fig 4
N
E
B
C
D
G
E
F
H
I
J
K
L
M
O
Q
A
B
C
I
G
F
H
G
Right Hand ViewLeft Hand View
Top View
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6. 1.1 Planes, Lines and Points.
As shown in Figure 1, there are three visible
planes or faces of the object namely:
a) ADEF
b) ADCB
c) DCGE
An edge or a line is an intersection of two
planes.
a) The Edge or line DA is the intersection of
planes ADCB and ADEF.
b) The Edge or line CB is the intersection of
planes ADCB and BCGH.
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7. 1.2 Hidden Details
The lines BH, GH and FH have been
represented by dash lines because these lines
are not visible. The following faces are visible.
a) ADEF
b) ADCB
c) DCGE
The faces of the object
a) ABHF
b) BCGH
c) GHFE
are also not visible.
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8. Exercise 1
1. a) State the hidden edges or lines in
Figures 2, 3 and 4.
b) State the visible and hidden planes or faces
of the objects in Figures 2, 3 and 4.
c) State the visible edges or lines in Figures 2,
3 and 4.
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9. 2. Orthographic Projection
Orthographic Projection is the two
dimensional views of an object based on:
a) the front view
b) The end view
c) The top view (plan)
As shown in figure 2 and taking the edge DA
of Fig 1 as reference point, the right hand
view is usually known as the front view.
The left hand view is the end view because
you are viewing the object from the left
hand side of the edge DA.
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10. Orthographic Projection
The plan is drawn by looking from the top of
the object taking the right hand view as
reference.
2.1 First Angle Projection
We shall start by drawing the First Angle
Projection of Figure 1. In Orthographic
Projections, the Front view is the
reference view.
10

11. Front View D, C E, G C,G E, D End View
A,B F, H B, H A, F
Plan
Fig 5 D,A E, F
C,B G, H
450
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11

12. Please take note of the position of the right
hand view and the front view on the first angle
projection.
As shown on figure 5, the front view is drawn on
the left hand side.
Similarly, the end view is drawn on the right
side of the front view. Imagine these views
being projected on a screen behind the object.
This is illustrated in Figure 6 below.
The plan is drawn below the front view. This is
based on the fact that you are looking at the
top view and projecting the plan on the screen
below.12/18/2017 12

13. The following observations are based on the
First Angle Orthographic Projection of fig 5.
2.1.1 Front View:
The Point C lies behind Point D. They are
actually the same point.
The Point G lies behind Point E. They are
actually the same point.
Similarly, the following pairs of points are the
same point.
Points A and Point B.
Point F and Point H.
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14. 2.1.2 End View:
Likewise, the following pairs of points are one
and the same point.
a)Points C and Point G.
b) Point D and Point E.
c) Point B and Point H.
d) Point A and Point F.
Point G is behind Point C.
Point E is behind Point D.
Figure out the last two pair of points based on
the diagrams.
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15. Exercise 2. *****************
Plan: You are required to
a)Points A and Point D.
b) Point B and Point C.
c) Point B and Point H.
d) Point A and Point F.
Point G is behind Point C.
Point E is behind Point D.
Figure out the last two pair of points based on
the diagrams.
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16. B
C
A
D
E
F
Y
H
Fig 6
Fig 8 Fig 9
G
Fig 7
Right Hand ViewLeft Hand View
Top View
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17. Front View End View
Fig 10 First Angle Projection of Fig 2 Fig 11a
Fig 12 Both holes are through holes Fig 13a
A
F
B
D
E
G
H
I
K
L
M
P
Q
D,C
E,G
A,B F,H
C,B
Plan D, A E,F
G,H
D,EC,G
A,FB,H
D C
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18. Fig 13b Isometric View (Hidden details)
A
B
C
DE
F
G
H
I
J
K
L
M
N
O
Fig 14 a First Angle projection of Fig 13
Plan
Front End
M,N P,O N,O M,P
L,K
I,J
H,G
P
E,F
A,B D,C B,C A, D
F,G E, H
J,K I,L
Fig 11b Isometric View (Hidden details)
A
B
C
D
E
F
G
H
I
J
K
L
M
N
O
P
Q
S
Fig 14 b Third Angle projection of Fig 13
Plan
End Front
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19. 12/18/2017 19

20. First Angle Projection Third Angle projection
Plan
Front
View
End
View
Plan
End
View
Front
View
Fig 14 a Fig 14 b
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21. 2.2 Third Angle Projection of Fig 13
The following statements explains Fig 14b.
In Third Angle projection:
a) The front view is drawn on the same side
from which it is viewed in the isometric
projection.
b) The end view is drawn on the same side from
which it is viewed.
c) Finally, the plan is projected and drawn above
the front view.
Observe the letter notation (fig 14a) that was
used to illustrate the simple object.
(fig 1 and fig 5)12/18/2017 21

22. The plan should be drawn in both First and Third
Angle projections by viewing from the Front
View in the isometric projection.
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23. Fig 3 Fig 4
70
50
80 70
50
60
40
40
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24. Fig 8 Fig 9
301010
60
15
80
2015
70
60
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