CE 100: CIVIL ENGINEERING DRAWING

Shaika Sharkia Lecturer, Department of Civil Engineering

University of Asia Pacific (UAP), Dhaka

ISOMETRIC PROJECTION

CHAPTER – 5

“Iso” means „equal‟ and

“metric projection” means

„a projection to a reduced

measure‟. An isometric

projection is one type of

pictorial projection in which

the three dimensions of a

solid are not only shown in

one view, but also their

dimension can be scaled

from this drawing.

ISOMETRIC PROJECTION

REGULAR HEXAGON

R

30o 45o

120o

120o

120o

B

D

C

H

E

F

G

A

1

1

1

2

30o 30o

Isometric Axes: AD, AE & AB

Isometric Lines: EH, BF etc.

Non-isometric Lines: DB

Isometric Planes: ADHE & 1 (in Fig. 1)

Non-isometric Planes: Plane 2 (in Fig. 2)

Fig. 1

Fig. 2

ISOMETRIC SCALE

Isometric Length = 0.81 × Actual Length

D

90o

B

C

0

1

2

3

3

2

1

0

45o 30o

A

AC

AB

2

1 = cos 45o =

AD

AB

2

3 = cos 30o =

= AC

AB

AD

AB

2

1

2

3

AC

AB×

AB

AD =

2

1×

3

2

AC

AD =

3

2 = 0.81

AD = 0.81 × AC

Draw the isometric projection of a rectangular prism of base 50 mm × 10 mm

and height 75 mm, when it rests with its base on H.P and one its of

rectangular faces is parallel to V.P

75 mm

DA CB

da cb

FRONT VIEW

50 mm

Aa Bb

Cc Dd

40 mm

TOP VIEW

3

2 1

1

2

3

Y

Z

R

X

45o 30o

a

b

c

d

A

B

C

D

30o 30o 30o 30o

Difference between Isometric Projection & Isometric View

Isometric View Isometric Projection

Drawn to actual scale Drawn to isometric scale

When lines are drawn parallel to

isometric axes, the true lengths

are laid off.

When lines are drawn parallel to isometric

axes, the lengths are foreshortened to 0.81

time the actual lengths.

ORTHOGRAPHIC

PROJECTION

ISOMETRIC

PROJECTION ISOMETRIC

VIEW

B

D

C

H

E

F

G

A

B

D

C

H

E

F

G

A

B

E F

A

Front View

D A

H E

Left View

B C

F G

Right View

D C

A B

Top View

C

H G

D

Back View

B

D

C

H

E

F

G

A

B

E F

A

Right View

D A

H E

Front View

B C

F G

Back View

D

C

A

B

Top View

C

H G

D

Left View

TO PREPARE ISOMETRIC VIEW

Box Method

Co-ordinate or Offset Method

Offset Method

Four-centre method

BOX METHOD

The isometric projection of solids like cube, square and

rectangular prisms are drawn directly when their edges

are parallel to the three isometric axes. The isometric

projection of all other types of prisms and cylinders are

drawn by enclosing them in a rectangular box. This

method is called Box method.

CO-ORDINATE METHOD OR OFFSET METHOD

The isometric projections of pyramids and cones are

generally drawn by Co-ordinate or Offset method

EXAMPLES OF BOX

METHOD

E

D

C

A′

E′

D′

C′

B′

A

B

30o 30o

B

C

D

E

A

1.5"

ISOMETRIC VIEW OF A REGULAR PENTAGONAL PRISM (Resting on one of its faces on H.P)

2.5"

F′

A′

E′

D′

C′ B′

E F

D

C A

B 30o 30o

ISOMETRIC VIEW OF A REGULAR HEXAGONAL PRISM (Resting on one of its faces on V.P)

D

B

C

D E

A

1.0"

3"

EXAMPLES OF FOUR-CENTRE

METHOD

C

R D

S

P A

B

Q

O1

O2

30o 30o

ISOMETRIC VIEW OF A CYLINDER (Lying on H.P)

1"

C

R

D

S

P

A B

Q

30o 30o

ISOMETRIC VIEW OF A CYLINDER (Lying on V.P)

1"

O1 O2

EXAMPLES OF CO-ORDINATE

OR OFFSET METHOD

The isometric view of a hexagonal pyramid of side of base 30 mm and

height 75 mm, when it is resting on H.P such that an edge of the base is

parallel to V.P

A

B

Q

C

R D

E

F

S

P

O

O1

A

B

C

D

E

F

O

O1

30 mm

y

F C

S E D R

P A B Q

OO1

F AE BD C

O

75 mm

Draw the isometric projection of a cone of base 40 mm diameter and

height 58 mm when it rest with its base on H.P

O

A BD

C

x

x

40 mm OO1

O

A B

C D

Q

R

S

P

O1

O

O1

A B

C D

Q

R

S

P

58 mm

DRAW FRONT, LEFT, RIGHT

& TOP VIEW FROM A

ISOMETRIC VIEW

30o 30o

6"

10"

10"

6"

6"

1′ – 6"

Landing

3′

Riser

Tread

1′ – 6"

1

10"

10"

1′ – 6"

TOP VIEW

FRONT VIEW 10"

10"

1′ - 6"

LEFT VIEW

3 ′

6 "

6"

6"

3 ′

6 "

6"

6"

½"

½"

½"

3"

1¼"

2¾"

2¼"

2

TOP VIEW

½"

2½"

FRONT VIEW LEFT VIEW

3"

½" 1¼"

½"

2¾"

3

1"

3½"

5½"

2¾"

3 ¾"

FRONT VIEW

5½"

3½"

11/8"

2¾"

LEFT VIEW

15/8"

3¾"

TOP VIEW

½"

½"

½"

½"

2.5"

1"

1"

1"

½"

½"

½"

4

½" ½" 1"

1"

1"

1"

TOP VIEW

½"

½"

½"

½"

½"

1.5" ½" ½"

FRONT VIEW

½"

½" 1"

½"

LEFT VIEW

1" 1" 1"

½"

½" 1"

½"

1" 1" 1"

RIGHT VIEW

5 1"

1"

½"

½"

1"

1"

1"

FRONT VIEW

½"

½"

½"

½"

1" 1"

TOP VIEW

1"

1"

1" 1"

LEFT VIEW

½"

½"

½"

½"

1" 1"

RIGHT VIEW

½"

½"

½"

½"

1" 1"

1"

1"

1"

1"

½"

½"

½"

1"

1"

½"

½"

1"

6

1 1 1

½

½

½

FRONT VIEW

1 1

½

½

½

LEFT VIEW

½

½

½

1 1

RIGHT VIEW

1

1

1 1 1

TOP VIEW

1 -6

10 -0

3 -0

3 -0

15 -0 2 -6

4 -8

5 -0

5 -0

2 -6

12 -6

16 -8

14 -6

7 -0

7

7 -0

2 -0

1 -0

3 -6

3@6 =1 -6

1 -0 5 -0 5 -0 5 -0 1 -0 1 -1 1 -1

FRONT VIEW

1 -0 3@10 =2 -6 3 -0 4 -9 4 -9

4 -0

3 -0

4 -6

3 -0

3@6 =1 -6

LEFT VIEW

Draw isometric view from the given orthographic projections.

Draw isometric view from the given orthographic projections.

Draw isometric view from the given orthographic projections.

Thank You