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Basic Technical Drafting - Auxiliary Views and Revolutions 1

Auxiliary Views and Revolutions -

Sacramento City College

Engineering Design Technology

2 Basic Technical Drafting - Auxiliary Views and Revolutions

Pictorial Drawing

Objects are generally described with three Normal Views (orthographic views):

Front view.

Top view.

Right Side view.

Pictorial Drawing

As long as the object has surfaces that align with one of the principal planes, the Normal views are sufficient.

Front view.

Top view.

Right Side view.

Pictorial Drawing

For objects with inclined surfaces, such as the separator, the three Normal Views are not sufficient!

For objects with inclined surfaces, the three Normal Views are:

Hard to draw.

Show the circles as ellipses.

Are hard to understand.

Auxiliary Views

When an object has an inclined surface, none of the regular views show the inclined part in its true size and shape.

Right Side

Inclined surface

Auxiliary Views

ONLY a View on a plane parallel to the inclined surface shows the true size and shape.

An Auxiliary View is used to show the true size and shape of an object that has surfaces that are not parallel to a principal plane.

Auxiliary Views

An auxiliary view is a projection on an auxiliary plane that is parallel to an inclined surface.

See Figure 7-3.

Auxiliary views provide a clear, undistorted image of the inclined surface on an object.

Auxiliary View

The auxiliary view looks directly at the inclined surface in a direction that is perpendicular to the surface.

See Figure 7-4a, 7-4b and 7-4c.

Figure 7-3a

Figure 7-3b

Figure 7-3c

Figure 7-3d

Figure 7-4a

Figure 7-4b

Auxiliary View

Figure 7-4C completely describes the object and only two views are required.

Front view

Auxiliary view

Figure 7-4c

Auxiliary Views

Auxiliary views are classified according to which of the three regular planes from which they are developed.

Auxiliary Views

Three auxiliary views exist

Front View

Top View

Right Side View

Each is developed by projecting as a primary reference the

Height

obtained from a normal view.

Figure 7-5a

Figure 7-5b

Figure 7-5c

Auxiliary Views

1. Front Auxiliary View

When an auxiliary view is hinged on the Front View, the view is known as the Front Auxiliary View.

The primary reference of the front auxiliary view is depth.

See Figure 7-6A.

Figure 7-6a

Auxiliary Views

2. Top Auxiliary View

When an auxiliary view is hinged on the Top View, the view is known as the Top Auxiliary View.

The primary reference of the top auxiliary view is the height of the object.

See Figure 7-6B.

Figure 7-6b

Auxiliary Views

3. Right Side Auxiliary View

When an auxiliary view is hinged on the Right Side View, the view is known as the Right Side Auxiliary View.

The primary reference of the right side auxiliary view is the width of the object.

See Figure 7-6C.

Figure 7-6c

Constructing an Auxiliary View

To construct any primary auxiliary view

1. Examine the normal views and look for the view that has the inclined surface.

2. Find the view that shows the edge view of the inclined plane.

The plane associated with this view is the reference plane, from which the auxiliary plane will be developed.

3. In this view, draw a light construction line at right angles to the inclined surface.

This line is the line of sight.

This line is the “hinge”.

4. Think of the auxiliary plane as being attached by hinges to the view from which it is developed.

5. From all important points on the reference view, draw projection lines at right angles to the inclined surface.

6. Draw a reference line parallel to the edge view of the inclined surface.

7. Transfer the depth dimension to the reference line.

8. Project the important points and connect them in sequence to form the auxiliary view.

Auxiliary Views

Symmetrical Objects

For symmetrical objects, the center-plane method is used.

Refer to Figure 7-8.

Procedure Steps:

1. Use a center plane as a reference plane.

2. Find the edge view of the inclined plane.

In Figure 7-8, the edge view of this plane appears as a centerline, XY, on the top view.

3. Label the points on the Top View for reference.

4. Transfer these points on the edge view of the inclined surface on the Front View.

5. Parallel to this edge view and at a convenient distance from it, draw the line X’ Y’.

6. In the Top View, find the distances from the numbered points to the centerline.

These are the depth measurements.

Transfer them onto the corresponding construction lines which you just drew.

Measure them off on either side of line X’ Y’

The result will be a set of points on the construction lines.

7. Connect and number the points on the construction lines to finish the Front Auxiliary View of the inclined surface.

Example:

Figure 7-31

Assignment:

Figure 7-55

Revolutions

When the true size and shape of an inclined surface do not show on a drawing, we can make an auxiliary view to find true lengths.

Use new reference planes to look at objects from new directions.

Revolutions

Another solution is to revolve (turn) the object.

The resulting drawing is called a Revolution.

The Axis of Revolution

In a revolution, use the regular reference planes X, Y and Z.

Imaging the object has been revolved to an angle that makes the principal features parallel to these planes.

To “revolve” the object:

Imagine that a shaft or an axis has been passed through it.

This imaginary axis is perpendicular to one of the three principal planes.

Figure 7-16

The axis the object is revolved around is called the axis of revolution.

Figure 7-16

The axis the object is revolved around is called the axis of revolution.

Figure 7-16

An object can be revolved

to the right (clockwise)

to the left (counterclockwise)

about an axis perpendicular to either the vertical or the horizontal plane.

See Figure 7-16.

Figure 7-16

The Rule of Revolution

The Rule of Revolution has two parts:

1. The view that is perpendicular to the axis of revolution stays the same except in position.

Figure 7-17

The Rule of Revolution

The Rule of Revolution has two parts:

2. Distances parallel to the axis of revolution stay the same.

Figure 7-17

Revolution About An Axis

Perpendicular to the Vertical Plane

Revolution - Axis Perp to Vertical Plane

Refer to Figure 7-18A.

The revolution axis is perpendicular to the vertical plane.

The front view is the same in size and shape.

The front view has a new position.

Figure 7-18a

The front and top views are shown in their normal positions.

The new front view is then shown, after the object has been revolved 45 degrees counter clockwise about an axis perpendicular to the vertical plane.

The new front view is the same in size and shape, except that it has a new position.

The new top view has been made by

Projecting up from the new front view and

Projecting across from the old top view.

The depth remains the same from one top view to another.

Perpendicular to the Horizontal

Revolution - Axis Perp to Horizontal Plane

Refer to Figure 7-18B.

The revolution axis is perpendicular to the horizontal plane.

The top view is the same in size and shape.

The top view has a new position.

The front and top views are shown in their normal positions.

The top view is then shown, after the object had been rotated 60 degrees clock wise about an axis perpendicular to the horizontal plane.

The new top view is the same in size and shape, as the old top view.

The new right-side view has been made by

Projecting down from the new top view and

Projecting across from the old front view.

The height remains the same from the original front view to the revolved front view.

Perpendicular to the Profile Plane

Revolution - Axis Perp to Profile Plane

Refer to Figure 7-18C.

The revolution axis is perpendicular to the profile plane.

The right-side view is the same in size and shape.

The right-side view has a new position.

The front and right-side views are shown in their normal positions.

The right-side view is the same in size and shape, except that it has a new position.

The new right-side view has been made by

Projecting down from the top view and

Projecting across from the new front view.

Note that the width remains the same from one front view to the other.

The depth remains the same from one top view to another.

Revolving an Object About the

Horizontal Axis

Figure 7-19

Revolving an Object About A

Vertical Axis

Figure 7-20

Revolving an Object Through a 45

Degree Angle

Figure 7-21

Partially Revolved Views

Figure 7-22

Successive Revolutions

After an object is revolved about an axis perpendicular to one plane, it can be revolved again about an axis perpendicular to another plane.

This process is called successive revolutions.

Figure 7-23

Industrial Applications

Figure 7-24

True Size and Shape

The true size of an inclined surface can be shown by:

An auxiliary view. The observer changes position.

A revolved view. The object changes position.

True Size and Shape

In a revolved view:

The inclined surface is turned until it is parallel to one of the principal planes.

It is as if the object has changed position.

True Size and Shape

In the auxiliary view:

The observer has changed position to look at the object from a new direction.

True Shape of an Oblique Plane

A surface shows its true shape when it is parallel to a plane.

Successive revolutions can be used to find the true shape of a surface.

True Length of A Line

Since an auxiliary view shows the true size and shape of an inclined surface, it can be used to find the true length of a line.

In D, the oblique plane 1-2-3-4 is shown.

It is oblique because it is inclined to all three of the normal planes.

Figure 7-29

True Length of A Line

You can revolve a line in any view to make it parallel to any one of the three principal planes.

Projecting the line on the plane to which it is parallel shows its true length.

Refer to Figure 7-30 F, G, H.

Single Revolution

An axis of revolution can be perpendicular to the vertical, horizontal or profile plane.

Summary

Use either the Auxiliary View or the Revolved View to find true length lines.

In the auxiliary view, it is as if the observer changed positions.

In the revolved view, it is as if the object changed positions.

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