In section drawings, all visible edges and contours behind the cutting plane
are shown. The exception is if the visible line or contour does not add to
clarity in the representation. Since sectional views are meant to replace or
define hidden lines, hidden lines should not appear in sectional views. The
exception to this edict is when the hidden line is necessary for clarity and
using it will allow you to omit a view.
Figure 3-62 illustrates correct and incorrect examples of lines in sectioning.
Figure 3-62.Correct and incorrect lines in a sectional view.
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