Auxiliary Views: Orthographic Projection

• An auxiliary view is an orthographic view where the lines of sight aren't parallel to the principal projection planes; frontal, horizontal, or profile
• There is an infinite number of possible auxiliary views for any given object
• The principal faces of the object aren't parallel to PP planes, or principal planes

Why Use Auxiliary Views?

• Inclined planes and oblique lines don't show their true length, or true size when using principle planes of projection
• True length of an oblique line, or the true size of an inclined plane can be determined by creating an auxiliary view
• The true shape and size of circular shapes are made clear with an auxiliary view

Steps of Drawing

• Decide which face will be drawn as:
  • A true surface
  • A true length line
  • An end view of a line
• Construction lines are drawn perpendicular to the surface, line, or point of interest so that enough space is left for the view
• A folding line is drawn at an appropriate distance to act as a reference plane
• Transfer distances from another / adjacent view
  • This view will typically adjoin the view from which the auxiliary is drawn from
• Visible and hidden lines are drawn, completing the view, matching the direction of projection lines

Steps of Drawing: Example 2

• Draw two orthographic views; assume a direction of sight for auxiliary view
• Draw construction lines parallel to the arrow
• Assume reference plane coincides with back surface, then draw; reference plane (edge view) in the top view and auxiliary view
• Draw auxiliary view of surface A transferring depth measurements from top view
• Add other visible edges and objects to complete the view

Curved Object

• Study the steps shown for an example curved object

Classifying Auxiliary Views

• Auxiliary views are classified according to the principal dimension of the object shown in the view
  • Depth/Front auxiliary view
  • Height/Top auxiliary view
  • Width/Side auxiliary view

Depth Auxiliary View

• Any auxiliary view projected from the 'elevation' showing depth of object
• Elevation is the adjacent view, Plan, and Side-View are alternative views

Height Auxiliary View

• Any auxiliary view projected from the plan showing height of object
• Plan is adjacent view, Side-View, and Elevation are alternative views

Width Auxiliary View

• Any auxiliary view projected from the side-view showing width of object
• Side-View is adjacent view, Plan, and Elevation are alternative views

Notes

• An auxiliary view is an orthographic view taken on planes other than principle projection (PP) planes; frontal, horizontal, or profile
• The principal dimension shown in an auxiliary view isn't shown in the adjacent view from which the auxiliary view is projected
• 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

Other Auxiliary Views

• Any auxiliary view projected from the primary auxiliary view is a secondary auxiliary view

True Length of a Line

• A line shows true length in a plane of projection which is parallel to the line
• To show a line's true length, make the fold line parallel to the line in question

Point View of a Line

• A line shows as a point view when projected onto a plane perpendicular to it
• To show a point view, choose the direction of sight parallel to the line where it shows true length

Edge View of a Plane

• A plane shows on edge in a plane of projection in which any line that lies entirely within the plane acts as a point view
• Choose the direction of sight parallel to a true length line lying in the plane

True Size of a Surface

• A surface shows its true size when projected onto a plane parallel to it
• Choose the direction of sight perpendicular to the edge view of the plane