Primary Auxiliary Views
Primary auxiliary view sometimes called helper view is used
to clearly and completely explain the shape of the object.
Most objects have sloping or inclined surfaces that are
not perpendicular to the plane of projection. Typical orthographic
view represents these surfaces as distorted and does not
show their true shape. When a sloping surface has an important
feature that should be shown without distortion, an auxiliary
view is used.
Since auxiliary view drawing usually shows only the true-shape
features and detail of the inclined surface, only partial
auxiliary view is necessary to be drawn.
How to make auxiliary view
The regular orthographic view has a line that represents
the edge of the inclined surface. The auxiliary view is
projected, at right angles, from this edge line and drawn
parallel to it.
Figure 2 shows the process of making an auxiliary view
of a symmetrical object.
1. The center plane (AB) is drawn parallel to the inclined
surface and it is used as representation of the reference
plane. This plane appears as a center line (A’B’)
on the top view.
2. The Points of intersection between the inclined surface
and the vertical lines on the top view are numbered, and
than transferred to the edge view of the inclined surface
on the front view.
3. In the top view distances C and D are found from the
numbered points to the center line, and then transferred
on the matching construction lines, measuring them off on
either side of the line AB.
4. Apply this step to other points.
5. Connect and number these points. This will result with
a front auxiliary view of the inclined surface.
Multi Auxiliary View Drawings
Some objects are more complex and may have more than one
surface not at right angles to the plane of projection.
These objects, may required auxiliary view for each such
surface. This kind of drawing is referred to as the multi
auxiliary view drawing.
Representation of circular features in auxiliary
Circular features in auxiliary projection appear elliptical,
not circular. The most commonly used method to draw the
true shape of the curved surface is the plotting of a series
of points on the line. The more points are plotted on the
line, the accuracy of the curve or circular feature is better.
The easiest way to explain this method of auxiliary projection
is the projection of a truncated cylinder. This shape seen
in the auxiliary projection is an ellipse, as shown in figure
The best approach to projection of a circular shape is
by plotting lines of intersection.
1. A center line (AB) of the auxiliary view is drawn parallel
to the edge line.
2. The parameter of the circle in the top view needs to
be divided into equal slices or equally spaced points. Our
example is divided in 24 equally spaced points, 15°
apart. The circumference of the circle (360°) is divided
in 24 equal spaces, 360°/24=15°.
3. These points are then projected down to the edge line
on the front view, then at right angles toward and past
the center line of the auxiliary view.
4. The widths between the center line and individual points
taken from the top view are transferred to the auxiliary
view. This is shown as lengths C and D for points 5 and
23 in Fig. 3.
5. When all the widths have been transferred from the top
view to the auxiliary view, the resulting points of intersection
are connected to give the preferred elliptical shape.
Some complex objects can be only described by using secondary
auxiliary view. The procedures for projecting and drawing
a secondary auxiliary view are the same as those for a primary
auxiliary view. Because of the complexity of their features
(usually inclined or sloping toward the plane of projection),
some objects require the drawing of partial front and top
views from which primary and secondary auxiliary views can
then be drawn. The auxiliary views can then be used for
finishing the top and front views.
Written by P.A