ENGINEERING GRAPHICS 1E7 Lecture 10: Auxiliary Views

Auxiliary View An auxiliary view is an orthographic view taken in such a manner that the lines of sight are not parallel to the principal projection planes (frontal, horizontal, or profile). There are an infinite number of possible auxiliary views of any given object.

Why Auxiliary View? Inclined planes and oblique lines do not appear true length or true size in any of the principle planes of projection To determine the true length of an oblique line or the true size of an inclined plane, an auxiliary view must be created.

Regular & Auxiliary Views Principal faces of the object are not parallel to PP planes. The auxiliary view shows the true shape and size of circular shapes.

Definition: Auxiliary Views An auxiliary view is an orthographic view taken on planes other than principal projection (PP) planes (frontal, horizontal, or profile). A primary auxiliary view is projected on the plane perpendicular to one PP plane and inclined to other 2 PP planes A secondary auxiliary view is projected from primary auxiliary views.

Auxiliary Plane Folding lines An auxiliary plane of projection is assumed parallel to the inclined surface. The auxiliary plane is perpendicular to the frontal plane of projection.

Steps of Drawing Select the face that is to be drawn as i) a true surface, ii) a true length line, iii) an end view of a line.

Steps of Drawing 2. Draw construction lines perpendicular to the surface/line/point of interest. This line should go in a direction, and far enough that leaves enough space for the view.

Steps of Drawing 3. Draw a folding line at an appropriate distance. This will act as a reference plane.

Steps of Drawing 4. Transfer distances from another view. This view will typically be the view adjoining the view that the auxiliary is drawn from.

Steps of Drawing 5. Complete the view. This method is called Folding-Line method.

Reference Plane Method Reference plane is a plane touching or cutting the object and is parallel to one of the PP planes.

Reference Plane Method The reference plane should be assumed in a position most convenient for transferring distances. Reference lines are always perpendicular to projection lines. A reference plane appears as a line in two alternate views and not in adjacent view. Measurements are made parallel to projection lines. In auxiliary view all points are at same distance from reference line as the corresponding points are in the alternate view.

Steps of Drawing Draw two orthographic views and assume a direction of sight for auxiliary view.

Steps of Drawing 2. Draw construction lines parallel to the arrow.

Steps of Drawing 3. Assume reference plane coinciding with back surface. Draw reference plane (edge view) in the top view and auxiliary view.

Steps of Drawing 4. Draw auxiliary view of surface A. Transfer depth measurements from top view.

Steps of Drawing 5. Complete the view by adding other visible edges and objects.

Notes Principal dimension shown in auxiliary view is the one not shown in the adjacent view from which auxiliary view is projected. Auxiliary view is similar to any other orthographic view. Reference plane method is advantageous to folding line method as fewer measurements are required to complete views.