Any view not projected onto one of the principal planes is an auxiliary view.
A primary auxiliary view is a view projected to a plane perpendicular to one
of the three principal planes (top, front, or side) and inclined to the other two
planes. A view projected from a primary auxiliary view on a plane inclined
to all three principal planes of projection is referred to as a secondary
The purpose of an auxiliary view is to show the true shape
and size of an inclined surface of an object since inclined surfaces are not
parallel to any planes in multiview projections and appear foreshortened.
The method of projecting the image of an object to an auxiliary plane is
identical to the method used for projecting an image to one of the principal
planes; that is, the projectors are parallel and the observer is positioned an
infinite distance away from the object.
To draw a primary auxiliary view, follow this table:
Draw two adjacent principal views, one of which must show the
inclined surface as an edge.
Lightly draw a reference line (AB) parallel to the edge view of the
Lightly draw a reference line (CD) between the two principal
views. Use AB and CD to locate points in the auxiliary view.
Draw projectors from the inclined edge rotating reference line AB
parallel with the inclined surface. These projectors are
perpendicular to the inclined edge and the reference line as shown
in figure 3-44.
Using a compass or dividers, transfer distances from reference line
CD to the various points in the side view.
Darken all object outlines of the primary auxiliary view and erase
all projectors and reference lines. The completed primary auxiliary
view shows the true shape of the inclined surface.
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