Problem 12.8 : Draw the projections of a circle of 50 mm diameter resting on the HP on point A

on the circumference. Its plane inclined at 45º to the HP and (a) The top view of the diameter AB

making 30º angle with the VP (b) The diameter AB making 30º angle with the VP

1a

2

34

5

6

7b

8

910

11

12

1’

a’2’

12’

3’

11’

4’

10’

5’

9’

6’

8’

7’

b’

1’

a’

2’

12’

3’

11’

4’

10’

5’

9’

6’

8’

7’

b’

X Y45º

11 a1

21

121

31

111

41

101

51

91

61

81

b171

30º

a111

21

121

31

111

41

101

51

91

61

81

b171

a1’11’21’

31’

41’

51’

61’b1’71’

81’

91’

101’

111’

121’

11

21

121

31

111

41

101

51

91

61

81

71

22’

32’

42’

52’

62’72’82’

92’

102’

112’

122’12’

Ø β

The difference in these two problems is in step 3 only.

In problem no12.8(a) inclination of TV of that AB is given, It could be drawn

directly as shown in 3rd step.

While in 12.8(b) angle of AB itself i.e. it’s TL, is given. Hence here angle of

TL(ab2) is taken, locus of b2 is drawn and then LTV I.e. a1 b1 is marked and

final TV was completed.Study illustration carefully.

b2

a1

b1