CENTER-LINES AND PRECEDENCE OF LINES
Center-lines are used to indicate the following:
1. Axes of symmetry for all the symmetrical portions of a view.
2. Axis of a cylinder or a cane.
3. Center of every circular curve must be located by two mutually perpendicular
center-lines. Generally these two center-lines are horizontal and vertical but , in
some cases, these may be circular and radial.
In any view, there are chances of coincidence of different types of lines. Hidden
portions may coincide with visible portions and center-line may be required where
already there is a -full line. Full lines have the first preference because visible features
are more prominent, on the second number are the dashed lines because these are
showing physical features though hidden, and then comes the imaginary lines like
cutting plane symbol and center-lines.
Most commonly cutting plane symbol is given more importance. A line having lower
order of preference is omitted in the portion where the other line with higher order of
preference is present.
