21) What do you mean by Break Lines ? 

It is used to limit a broken section. For short break an uneven freehand thick line is recommended and for long breaks a long thin ruled dashes joined by freehand ‘ Zig Zags’ are used.

22) What are Phantom Lines ?

These are thin lines composed of long dashes with pair of short dashes. Phantom Lines used to show adjacent parts, alternate positionsand the lines of motion.

23) State the difference between Size dimension and Location dimension ?

(a)Size Dimension :It describes the size of an object such as length ,width, thickness, depth, diameter etc.
(b)Location Dimension: A location dimension describes the location of constructional parts within an object .It includes location of holes, slots, grooves etc.

24) What is a functional dimension ?

This is expressed directly on the drawing which is essential to the function of the product.

25) What is the main advantage of chain dimensioning ?

Chain dimensioning can be used where the possible accumulation of tolerance does not cause danger to the functional requirement of the part.

26) Where is draft angle used ?

Generally draft angle is used in moldings and drop forgings, parts of which maybe left un-machined.

27) How are screw threads specified ?

It should be specify pitch and dimension with tolerances and also the distance to the end of full(parallel)threads.

28) What is a Polygon ?

It is plane closed figure having many sides and angles. A regular polygon has equal sides and equal angles.

29) Define Ellipse ?

It is a plane curve formed by a point moving so that the sum of its distances from two fixed points (foci) is constant and equal to major axis.

30) Define Parabola ?

Parabola is a curve which is generated by a point moving along a path equidistant from a point (focus)and a straight line(directrix).