engineering graphics

1. PROJECTIONS OF PLANES
A plane is a two-dimensional geometrical entity
It has length and width but no thickness
For practical purposes, a flat face of an object may be treated as a
plane
Information usually given:
1. Shape of the plane
2. Inclination of it’s surface with one of the reference planes
3. Inclination of one of it’s edges with the other reference plane will
be given
1

2. POSITIONS OF PLANES
1. Plane parallel to one RP and perpendicular to other
Case (i): Plane in the HP and away from the VP
Case (ii): Plane in the VP and away from the HP
Case (iii): plane away from both the RPs and parallel to HP and perpendicular
to VP
Case (iv): plane away from both the RPs and parallel to VP and perpendicular
to HP
2. Plane inclined to one RP and perpendicular to other
Case (i): plane away from both the RPs and inclined to HP and perpendicular
to VP
Case (ii): plane away from both the RPs and inclined to VP and perpendicular
to HP
3. Plane inclined to both the planes

3. CASE OF A RECTANGLE
SURFACE PARALLEL TO HP AND PERPINDICULAR TO VP
VP
For T.V.
a’ d’
b’ c’
For
F .V.
a d
b c
HP

4. CASE OF A RECTANGLE
SURFACE INCLINED TO HP AND PERPINDICULAR TO VP
VP d’
c’
For Tv
a’
b’
For
Fv a1 d1
b1 c1
HP

5. CASE OF A RECTANGLE.
SURFACE INCLINED TO HP AND INCLINED TO VP
For T.V. VP
d1’ c1’
a1’ b1’
d1
Fo
r F. V
. c1
a1
5
HP b 1

6. Rectangle 30mm and 50mm Read problem and answer following questions
sides is resting on HP on one 1. Surface inclined to which plane? ------- HP
small side which is 300 inclined 2. Assumption for initial position? ------// to HP
to VP,while the surface of the 3. So which view will show True shape? --- TV
plane makes 450 inclination with 4. Which side will be vertical? ---One small side.
HP. Draw it’s projections. Hence begin with TV, draw rectangle below X-Y
drawing one small side vertical.
Surface // to Hp Surface inclined to Hp
d’c’ c’1 d’1
c’d’
a’b’
a’ b’ 450 b’1 a’1 Y
X 300
a a1 d1
a1
d Side
Inclined
to Vp
b1
b c b1 c1
d1
6
c1

7. A regular pentagon of 30 mm sides is resting Read problem and answer following questions
on HP on one of it’s sides while it’s opposite HP
1. Surface inclined to which plane? -------
vertex (corner) is 30 mm above HP. 2. Assumption for initial position?//HP
------
Draw projections when side in HP is 300 TV
3. So which view will show True shape? ---
inclined to VP. Hence begin with TV,draw pentagon below
X-Y line, taking one side vertical.
SURFACE INCLINATION INDIRECTLY GIVEN
SIDE INCLINATION DIRECTLY GIVEN:
ONLY CHANGE is
the manner in which surface inclination is described:
One side on Hp & it’s opposite corner 30 mm above Hp. d’ d’1
Hence redraw 1st Fv as a 2nd Fv making above arrangement.
Keep a’b’ on xy & d’ 30 mm above xy. c’e’ c’1
30 e’1
X b’ a’ c’e’ d’ a’
b’ a’1 b’1 Y
300
e1 a1
e
e1
a a1 b1
d d1
d1 c1
b b1
c c1 7

8. CIRCULAR LAMINA INCLINED AT AN ANGLE 45O TO FRONTAL PLANE
AND PERPENDICULAR TO TOP PLANE (USE IIIRD. ANGLE)
• Since the circular lamina is (Tutorial 5, qs. 3)
TV: Top View
to be inclined at 45 to the
o
frontal plane (FV), draw it FV: Front View
initially parallel to the frontal d, f
e
T d, f
e
plane. T c, g c, g
b,h b, h
45O 45O
• Next, rotate the TV by 45o a e a
b, h c, g d, f
and draw an identical new
TV
• For projection, divide the c’
c’
circle in FV into sections b’ d’ b’ d’
and project the points in the
a’ e’ a’ e’
TV
• With a as center and ab, ac, h’
g’
f’ h’ f’
ad as radii, draw arcs to the F F g’
new positions.
• Project corresponding From the new TV project points into
points into the new TV and the new FV to get points on the
circumference of the lamina 8
FV

9. Drawing the side view
w
w
T
F O w
T 45o
F O w
RSV
RSV
With O as center draw curves (1/4
Draw a line from O at 45o to the
circle) to project the corners
horizontal axis to project the corners
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10. Examples of projections of a triangular plane
III rd angle
X X A X X
TV TV TV TV
C
B A A C B
B C B
3 cm
A
Z Z Z Z
A A
3 cm A
B
B C
A C
B C B C
Y FV Y FV FV FV
Vertical plane 3 Horizontal Inclined plane Oblique plane (not
cm from frontal plane 3 cm perpendicular perpendicular to any
plane from top plane to top plane principal plane)
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