There are many times when the interior details of an object cannot be seen from the outside (figure 9). It should not really be a surprise that
a convention is required to give additional details
about the interior of an object. Many common
examples can be seen every day - items that look
as though they may be constructed In similar
ways when viewed solely with the information
available from the outer surface.
We can get around this by pretending to cut the object on a plane and showing the “sectional view“. The sectional view is applicable to objects like engine blocks, where the interior details are
intricate and would be very difficult to understand through the use of "hidden" lines (hidden lines are, by convention, dotted) on an orthographic or isometric drawing.
Imagine slicing the object in the middle (figure 10)
Take away the front half (figure 10) and what you have is a full section view - In isometric section and in orthographic section (figure 11)
Orthographic drawings are also essential when patent drawings are filed as details within these can describe features far better than words alone. These are also labelled.
Engineering Drawing and Sketching