Auxiliary Views Chapter 7

Overview Revolution Revolved Auxiliary Most objects that are designed and manufactured do not conform to convenient rectangular or cylindrical shapes that require only the normal views. Many objects have surfaces that are slanted in one or more directions. You can show the true size of an inclined surface by either an auxiliary (additional) view, as shown in Figure A below, or a revolution, or revolved view, as shown in Figure B below, and Figure C. In a revolved view, the inclined surface is turned until it is parallel to one of the principal planes. In the auxiliary view, it is as if the observer has changed position to look at the object from a new direction. Conversely, in the revolved view, it is as if the object has changed position. Both auxiliaries and revolutions help you visualize things better. They also work equally well in solving problems. to show the true size and shape of inclined surfaces.

Normal Views vs. Auxiliary Views When an object has an inclined surface, none of the normal views shows the inclined part in its true size and shape. See left. However, a view on a plane parallel to the inclined surface does show its true size and shape, as shown in the figure at right.

Basic Relationship of the Auxiliary Plane to the Normal Planes An auxiliary view is a projection on an auxiliary plane that is parallel to an inclined surface, as shown in below. It is a view that looks directly at the inclined surface in a direction perpendicular to it. Auxiliary views provide a clear image of the inclined surfaces on an object.

Example Anchor with a slanting surface An anchor with a slanting surface is pictured in Figure A.

Auxiliary Normal The three normal views are shown in Figure B. Not only are these views hard to draw and understand, but they also show three circular features of the anchor as ellipses. In Figure C, the anchor is described completely in two views, one of which is an auxiliary view.

Example Simple Inclined Wedge In Figure A, a simple inclined wedge block is shown in the normal views. In none of these views does the slanted surface (surface A) appear in its true shape. In the front view, all that shows is its edge line MN.

In the side view, surface A appears, but it is foreshortened In the side view, surface A appears, but it is foreshortened. Surface A is also foreshortened in the top view. Line MN also appears in both views, but looking shorter than its true length, which shows only in the front view. To show surface A in its true size and shape, you need to imagine an auxiliary plane parallel to it, as shown in Figure B left. Figure C right shows the auxiliary view revolved to align with the plane of the paper. By following this method, you can show the true size and shape of any inclined surface.

Primary Auxiliary View

Primary Auxiliary View Front Auxiliary Auxiliary views are classified according to their origin and which of the three normal planes they are developed from. A primary auxiliary view is one that is developed directly from the normal views. There are three primary auxiliary views. Each is developed by projecting as a primary reference the height, width, or depth obtained from a normal view. The next three figures below show the three primary auxiliary views. When an auxiliary view is hinged on the front view, the view is a front auxiliary view. The primary reference of the front auxiliary view is depth. An example is shown in Figure A.

Primary Auxiliary View Top Auxiliary An auxiliary view that is hinged on the top view is a top auxiliary review, as shown in Figure B.

Primary Auxiliary View Right-Side Auxiliary The primary reference of the top auxiliary view is the height of the object. Finally, a view hinged on the right-side view is a right-side auxiliary view. Its primary reference is the width of the object, as shown in Figure C.

Partial Auxiliary Views

Partial Auxiliary Views If you use break lines and centerlines properly, you can leave out complex curves while still describing the object completely, as shown in the figure below. An auxiliary view in which some elements have been left out is known as a partial auxiliary view. In the figure below, a half view is sufficient because the symmetrical object is presented in a way that is easy to understand.

Auxiliary Sections

Auxiliary Sections Sometimes it is useful to show a sectional view of an object. When the cutting plane is not parallel to any of the normal views, the section is known as an auxiliary section. In the figure below, the auxiliary section was located by using the cutting plane represented in edge view by line AA.

STEPS TO CREATE AUXILIARY VIEWS The process of creating an auxiliary view in a two-dimensional CAD drawing is similar to that used in board drafting. However, auxiliary views can usually be drawn in less time because the CAD software provides commands that automate many of the more time-consuming tasks. The next six figures show the procedure for creating an auxiliary view using AutoCAD. Follow these steps:

1. Create the front and side views and a partial top view, as shown in Figure A. Do not dimension the views.

2.Create a construction line perpendicular to the line that represents the inclined plane at the lower end of the inclined line in the front view. To do this, pick the two endpoints of the short end line, as shown in Figure B.

3. Copy the construction line to each important point in the front view. See Figure C.

4.Copy the inclined line to another location on the construction lines, as shown in Figure D. Use the Nearest object snap to ensure that the endpoint of the inclined line is exactly on the lowest construction line.

5. Offset the line you created in step 4 to the right by the depth dimension, .76, as shown in Figure D. This defines the depth of the object in the auxiliary view.

6. Trim the construction lines to form the other boundaries of the auxiliary view. Use the Layer Control above the drawing area to move the lines to their appropriate layers: Hidden, Centerline, etc. See Figure E.

7. Add the other centerline, the hole, and other details based on the dimensions given in Figure A above. The finished drawing should look like the one in Figure F.