# AUXILIARY PROJECTIONS

TOPIC: AUXILIARY PROJECTION
INTRODUCTION
In orthographic projections, the principal planes of projection – horizontal and vertical planes are usually employed.
Apart from these planes, imaginary planeswhich are not perpendicular to the principal planes are oftenintroduced and used. These aiding or helping planes otherwise called auxiliary planes, when placed at right angles to the direction of view, in the same that normal elevations and plans are at right angles to the horizontal and vertical planes, help the viewer to see clearly other sides of the object not parallel to the principal planes.
Such views projected to the auxiliary planes are called auxiliary views. An auxiliary view projected from an elevation will give an auxiliary plan while an auxiliary view got from the plan will give an auxiliary elevation. An auxiliary view projected from an auxiliary elevation is called second auxiliary plan. A second auxiliary elevation can be projected also from first auxiliary plan.

AUXILIARY PLANE
The auxiliary plane can be at angle to the vertical plane or horizontal plane.
The line of intersection between the horizontal plane and auxiliary plane is called horizontal trace while the line of intersection between the vertical plane and auxiliary plane is called vertical trace.

(DRAWING OF AUXILIARY PLANE)

A. TO DRAW THE AUXILIARY PLAN AND ELEVATION OF A GIVEN SQUARE PRISM
Procedure
1. Draw the given views – elevation and plan.
2. Draw lines x1y1 and x2y2 representing the vertical and horizontal auxiliary planes.
3. Project lines from all ponts on the plan or elevation, parallel to the line of sight (if it is given or ) at right angles to the auxiliary plane line.
For auxiliary elevation, make use of distance b and for auxiliary plan, make use of distance a.
Consider the lines one by one, looking in the direction of line of sight to note lines visible and not visible.