Page 20 - CITS - ED - Mechanical

ENGINEERING DRAWING - CITS

• C as centre and radius 30 (R10 + R20), draw arcs cutting the arcs R35 at C and C .
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• C and C as centers, with R20, draw arcs forming the arc tangential curves to the circles.
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Exercise 1.10 to 1.12
Follow the procedures of the above exercises and draw the parts involving circles and arcs available in the work
book. (Ex.1.10 to 1.12)
Exercise 1.13

Construct an ellipse by concentric circle method. Major axis 80 mm. Minor axis 40 mm. (Fig 10)

Fig 10

• Draw the major axis AB (80 mm) and minor axis CD (60 mm), bisecting at right angle at 0.
• '0' as centre OA and OC as radius, draw two concentric circles.
• Draw a number of radial lines through '0' (say 12) cutting the two circles.
• Mark the points on the outer circle as a,b,c.

• Similarly mark the corresponding intersecting points on inner circle as a',b',c'.
• From points such as a,b,c... draw lines parallel to minor axis.
• From points such as a', b',c'.... draw lines parallel to the major axis to intersect with the corresponding vertical
lines at points P , P P .... etc.
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• Join all these points with a smooth curve by free hand or using "french curve" and form the ellipse.
• To find the 'Foci' - with half the major axis (a) as radius and with 'C' on the minor axis as centre, draw an arc
cutting the major axis, at two points, mark them as F F the focus points of the ellipse.
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Exercise 1.14
Construct an ellipse by four centre method - Major axis = 80 mm and Minor axis = 40 mm - Type A. (Fig 11)
• Draw the major axis A A and minor axis B B .
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• Set off B M and B M equals to A B .
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• Join A B and set off B B equal to a-b (a = OA , b = OB )
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• Draw a bisector on A B which intersects A A at M .
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• Similarly obtain M . M & M as centres and B M as radius, draw arcs P P & P P .
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• M M as centres and M P as radius, draw arcs P P & P P and complete the ellipse.
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CITS :Engineering Drawing (Mechanical) - Exercise 1