Short Answer:

An auxiliary view is a special type of projection used in engineering drawings to show the true shape and size of an inclined surface. When a surface is tilted and not parallel to the main projection planes (front, top, or side), it appears distorted in those views. To see its real size, we draw an auxiliary view.

To construct an auxiliary view, we project lines perpendicular to the inclined surface from the main view, and then we transfer distances from the adjacent views to the auxiliary plane. This method helps engineers understand the exact shape and measurements of slanted surfaces for proper manufacturing.

Detailed Explanation:

Constructing an Auxiliary View for an Inclined Surface

In technical drawing, especially in mechanical engineering, some parts of an object may have sloped or inclined surfaces. These surfaces do not appear in true size when seen from the standard views (front, top, or side). Instead, they look shortened or distorted. To overcome this problem and to read the exact shape and size, an auxiliary view is constructed.

An auxiliary view is a projected view that is drawn on a plane that is perpendicular to the inclined surface. It gives a clear and undistorted view of that surface.

Steps to Construct an Auxiliary View

Let’s go step-by-step to understand how to draw it correctly:

1. Draw the Principal Views (Front, Top, or Side)

Start by drawing the basic views (like front and top). Make sure the inclined surface is clearly shown in at least one of these views. Usually, the front view shows the inclination angle.

2. Identify the Inclined Surface

From the principal view (generally front), locate the slanted surface that is not parallel to any projection plane. Note how it looks foreshortened—this means it does not show true length.

3. Draw the Reference Line (X₁Y₁)

Draw a line called X₁Y₁ which is perpendicular to the inclined surface. This will act as the base line or folding line for the auxiliary view. You will project onto this plane.

4. Project Points Perpendicularly from Inclined Surface

Now from each point or corner on the inclined surface in the front view, draw projection lines perpendicular to the inclined surface towards the auxiliary view. These are construction lines and should be light in weight.

5. Transfer Heights or Depths from Adjacent View

Go to the top view (or side view, depending on orientation) and measure the distances of the same points from the X–Y line. Transfer these distances along the projection lines in the auxiliary view. This step helps in maintaining the true proportion.

6. Join the Projected Points

After marking all the transferred points, join them in the same order as in the original view. This completes the auxiliary view of the inclined surface, showing its true shape and size.

7. Label and Dimension

Clearly label all the points, and add dimensions if required. The view should be neat, labeled as “Auxiliary View”, and easy to interpret.

Why Auxiliary Views Are Important

• Help in visualizing sloped surfaces
• Show the true shape that is hidden or distorted in standard views
• Provide accurate details for cutting, machining, or inspection
• Essential for technical drawings involving angles

This is especially useful in parts like inclined plates, ramps, sloped holes, or angled cuts.

Example: Slanted Plate on a Block

Suppose you have a rectangular block, and one face is cut at an angle. In the front view, it appears as a slanted line, and in the top view, it looks like a rectangle. To find the true shape of the slanted surface, you construct an auxiliary view by projecting perpendicular from the slanted edge and measuring the depth from the top view. This gives the real triangular shape of the inclined surface.

Conclusion

Constructing an auxiliary view for an inclined surface is an important method in engineering graphics. It helps reveal the true shape and size of any surface that appears distorted in normal views. By projecting lines perpendicular to the inclined surface and transferring distances from other views, engineers can draw accurate and useful auxiliary views. This improves the clarity, precision, and usefulness of technical drawings used in design and manufacturing.