chapter 5 auxiliary view_handout

BDU; Institute of Technology Lecture Note on Engineering Drawing

School of Mechanical & Industrial Engineering Chapter 5, Auxiliary Views

Compiled By; Alemayehu M. 1

CHAPTER 5

AUXILIARY VIEWS

Chapter Objectives

Upon completion of this chapter you will be able to accomplish the following:

Identify the need for auxiliary views in order to show the actual shape, size, and

relationship of an angled part feature.

Differentiate between and demonstrate ability to produce primary and secondary

auxiliary views using the fold line method and the reference plane method.

Develop the ability to produce partial, half, and complete auxiliary views.

Produce views to show the true length of a line, point view of a line, edge view of a

surface, and true size view of a surface

Outline

5.1 Introduction

5.2 Drawing Auxiliary Views

5.2.1 Drawing auxiliary views using folding line method

5.2.2 Drawing auxiliary views using reference plane method

5.2.3 Drawing auxiliary views of curved surfaces

5.3 Classification of Auxiliary View

5.4 Applications of Auxiliary View

5.4.1 Reverse construction

5.4.2 True length of a line

5.4.3 Point view of a line

5.4.4 Edge view of a plane

5.4.5 True size of a plane




5.1 Introduction

When creating engineering drawings, it is often necessary to show features in a view

where they appear true size so that they can be dimensioned. The object is normally

positioned such that the major surfaces and features are either parallel or perpendicular to

the principal planes. Views are normally selected so that most of the features will be

visible in the three principal views. The front, top, and left or right side views are most

commonly drawn.

Many objects are quite complex, and the three principal views may not best present the

geometry of the part. Certain features may not appear true size and shape in those views,

or may be hidden. In this case one or more auxiliary views typically are drawn.

An Auxiliary View is an orthographic view that is projected onto any plane other than the

frontal, horizontal (top), or profile (side) plane.

An auxiliary view is not one of the six principal views. To show the true size and shape of

inclined surface, an auxiliary view can be created by positioning a line of sight

perpendicular to the inclined plane, then constructing the new view. There are an infinite

number of possible auxiliary views of any given object. Imagine an object in a fixed

position. As an observer, you are free to move around the object. You can look at the

object so that certain features are visible and also true size and shape. The number of

possible views is infinite. Determining which views to provide is a critical decision. Too

many views can make a drawing difficult to read and more expensive to create. Omitting

views that provide true size views of features will make it impossible to correctly

dimension the drawing. Realize that the person producing the part will have to turn it as it

is being made. One should provide views that will aid in production and give a

representation of the geometry of the object.

Primary auxiliary views are projected from one of the principal views. A primary

auxiliary view is perpendicular to one of the three principal planes and inclined to the other

two. Secondary auxiliary views are projected from a primary auxiliary view and are

inclined to all three principal planes of projection. Successive auxiliary views are

projected from secondary auxiliary views.




5.2 Drawing Auxiliary Views

Despite the fact that auxiliary views are projected onto planes which are inclined to the

principal projection planes, they are still classified as orthographic views. The lines of

sight are still parallel to each other and perpendicular to the plane of projection. Therefore,

when reading lines on the object in an auxiliary view adjacent to a principal view, the

same rules apply to reading lines in adjacent principal views.

To utilize an auxiliary view to show a surface true size (TS), a view must exist or be drawn

where that surface appears as a line. It is not possible to show an oblique surface TS in a

primary auxiliary view. Once a given or constructed view showing the surface as a line is

identified, projecting that surface onto a plane parallel to it will show its TS.

Generally there are two methods to draw auxiliary views:

I. Fold Line Method

II. Reference Plane Method

5.2.1 Drawing Auxiliary Views Using Fold Line Method

In fold-line method, the object is suspended in a glass box, as shown in figure 5.1, to

show the six principal views, created by projecting the object onto the planes of the box.

The box is then unfolded, resulting in the six principal views. However, when the six

views are created, surface ABCD never appears true in size and shape; it always appears

either foreshortened or on edge.

To get surface ABCD in true size and shape, the object suspended inside a glass box,

which has a special or auxiliary plane that is parallel to inclined surface ABCD, as shown

in figure 5.2. The line of sight required to create the auxiliary view is perpendicular to the

new projection plane and to surface ABCD.

The auxiliary glass box is unfolded with the fold lines between the views shown as

phantom lines. In the auxiliary view, surface ABCD is shown true in size and shape and is

located at distance M from the fold line. The line AB in the top view is also located at

distance M from its fold line.




Figure 5.1 A glass box unfolded resulting principal views

Figure 5.2 A glass box with auxiliary plane




I. To draw primary auxiliary view using folding line method

A primary auxiliary view is one that is adjacent to and aligned with one of the principal

views. Primary auxiliary views are identified as front-adjacent, top-adjacent, or side-

adjacent to indicate the principal view with which it is aligned (and projected from). In

industry, auxiliary views are used to show aspects of a mechanical part or portions of a

system such as piping configurations or structural bracing that cannot be adequately

represented in the three principal views. The block, shown in Figure 5.3, required

auxiliary views to clarify the true shape and size of the inclined surfaces. For this part, the

three principal views (top, front, side) do not provide true shape/size views of the inclined

surface. It is necessary to project primary auxiliary views to describe the angled face in

detail. To show the true size and shape of the inclined surface, an auxiliary view can be

created by positioning a line of sight perpendicular to the inclined plane, then constructing

the new view, as shown in figure 5.4.

Figure 5.3 A bock with inclined surface

Figure 5.4 Observer’s position (direction of sight) for auxiliary views




The following steps describe the projection of the primary auxiliary view (in this case

frontal auxiliary view) of object shown in the figure 5.3 using fold line method:

STEP- 1. Select the surface that is to be drawn as a true surface and draw the

folding lines between the principal views. In this case the folding line between the front

and top view would be enough.

STEP- 2. Draw construction lines (projection lines) perpendicular to surface of

interest. This line should go in a direction, and far enough that leaves enough space for

the view.




STEP- 3. Draw the auxiliary folding line perpendicular to the construction lines

(projection lines); drawn from the inclined surface and at any convenient place.

STEP – 4. Transfer distances from another view (adjacent view).

This view will typically be the view adjoining the view that the auxiliary is drawn from. In

this case the distances (depth) are transferred from top view.




STEP – 5 Complete the view. Draw visible and hidden lines as seen from the direction of

projection lines.

II. To draw secondary auxiliary view using folding line method

A secondary auxiliary view is the one that is adjacent to and projected from a primary

view. As shown in the figures below, from primary auxiliary view 1, a secondary auxiliary

view 2 can be drawn; then a third auxiliary view 3 and so on. An infinite number of such

successive auxiliary views may be drawn.

To draw the secondary auxiliary view 2 in figure below, drop the front view from

consideration, and center attention on the sequence of three views: the top view, view 1

and view 2.




The follow steps describe the projection of secondary auxiliary view from primary auxiliary

view as shown in the figure below.

STEP – 1 Draw the primary auxiliary view 1 as discussed before.

STEP – 2 Draw arrow 2 toward view 1 in the direction desired for view 2 and draw

projection lines parallel to the arrow & auxiliary folding line V1/ V2 perpendicular to the

projection lines.




STEP – 3 Locate all numbered points in view 2 from folding line V1/ V2 as the same

distance as they are in the top view from folding line H/1. For example, transfer distance

‘b’ to locate point 4 and 5.

STEP – 4 Complete the view by connecting points with straight lines and determining

visibility. The corner nearest the observer (11) for view 2 will be visible, and the one

farthest away (1) will be hidden, as shown.




To draw views 3, 4, 5, etc, as shown in the figure below, repeat the above procedure,

remembering that each time we will be concerned only with a sequence of three views.

Figure 5.5 successive auxiliary views

5.2.2 Drawing Auxiliary View Using Reference Plane Method

The reference plane method is a technique that locates a plane relative to the object

instead of suspending the object in a glass box. In section 5.2.1, the folding lines are edge

views of the frontal plane of projection. In effect frontal plane is used as a reference plane

or datum plane, for transferring distance (depth measurements) from the top view to the

auxiliary view. Instead of using one of the planes of projection as a reference plane, it is

often more convenient to assume a reference plane inside the glass box parallel to the

plane of projection and touching or cutting through the object, as shown in the figure 5.6.

The reference plane may coincide with the front surface of the object as at (a), or it may

cut through the object as at (b) if the object is symmetrical, or the reference plane may

coincide with the back surface of the object as at (c) or through any intermediate point of

the object. The reference plane should be assumed in the position most convenient for

transferring distance with respect to it.




When using reference plane method, remember the following:

Reference lines, like folding lines, are always at right angle to the projection line

between the views.

A reference plane appears as a line in two alternative views, never in adjacent

views.

Measurements are always made at right angles to the reference lines, or parallel to

the projection lines.

In the auxiliary view all points are as the same distance from the reference line as

the corresponding points are from the reference line in the second previous view or

alternative view.

Figure 5.6 Position of reference plane

The following steps describe the projection of the primary auxiliary view of the object

shown in Figure 5.7 using reference plane method:

Figure 5.7




STEP – 1 Draw two orthographic views and assumes a direction of sight for

auxiliary view.

STEP – 2 Draw construction lines parallel to the arrow.

STEP – 3 Assume reference plane coinciding with back surface. Draw reference

plane (edge view) in the top view and auxiliary view.




STEP – 4 Draw auxiliary view of surface A. Transfer depth measurements from

top view.

STEP – 5 Complete the view by adding other visible edges and objects.

Secondary auxiliary views have already been presented using the folding line method.

Here, after the primary auxiliary view is drawn using the reference plane method, the

secondary auxiliary view will be projected from the primary auxiliary view as discussed

before in folding line method.




5.2.3 Drawing of Auxiliary Views of curved surfaces As discussed in multiview projection section, if a cylinder is cut by an inclined plane, the

inclined plane is elliptical in shape. However, as shown in the figure 5.8, the ellipse does

not show true size and shape in principal views. Taking the line of sight perpendicular to

the edge view of the inclined plane, the resulting ellipse is shown in true size and shape

in the auxiliary view.

The steps shown in the figure 5.8 describe the projection of auxiliary view using

reference plane method. The steps are similar with those discussed in section 5.2.2.

Note that since this a symmetrical object, the reference plane is assumed through the

center as shown. To plot points on the ellipse, select points the circle of the side view,

and project them across the inclined surface, then upward to the auxiliary view. In this

manner two points can be projected each time, as shown for points 1-2,3-4,5-6,7-8,9-10.

Figure 5.8 Steps of drawing auxiliary view of curved surface




5.3 Classification of Auxiliary View

Auxiliary views are created by positioning a new line of sight relative to the object. It is

possible to create any number of auxiliary views, including a new auxiliary view from an

existing auxiliary view. Therefore, auxiliary views are first classified as: primary,

secondary, or tertiary (see figure 5.9)

I. Primary auxiliary view is a single view projected from one of the six principal

views. A primary auxiliary view is perpendicular to one of the three principal

planes and inclined to the other two.

II. Secondary auxiliary view is a single view projected from a primary auxiliary

view and is inclined to all three principal planes of projection.

III. Tertiary auxiliary view is a single view projected from a secondary or another

tertiary auxiliary view.

Figure 5.9 Primary, Secondary and Tertiary auxiliary views




Depending on the principal view from which they are projected, primary auxiliary views

are divided into three types; Depth auxiliary view, Height auxiliary view and width auxiliary

view.

I. Depth auxiliary view (frontal auxiliary view) is projected from the front view, and the

depth dimension is shown true length. An infinite number of auxiliary planes can be

assumed perpendicular to and hinged to the frontal plane (F) of projection. Five such

planes are shown in figure 5.10. In all of these views the principal dimension, depth, is

shown; hence all of the auxiliary views are depth auxiliary views.

Figure 5.10Depth auxiliary views II. Height auxiliary view (horizontal auxiliary view) is an auxiliary view projected from

the top view, and the height dimension is shown true length. An infinite number of

auxiliary planes can be assumed perpendicular to and hinged to the horizontal plane (H)

of projection. Five such planes are shown in figure 5.11. In all of these views the principal

dimension, height, is shown; hence all of the auxiliary views are height auxiliary views.




Figure 5.11 Height auxiliary views

III. Width auxiliary view (profile auxiliary view) is an auxiliary view projected from the

profile view, and the width dimension is shown true length. An infinite number of auxiliary

planes can be assumed perpendicular to and hinged to the profile plane (P) of projection.

Five such planes are shown in figure 5.12 In all of these views the principal dimension,

width is shown; hence all of the auxiliary views are width auxiliary views.

Figure 5.12 Width auxiliary views




In auxiliary views, it is normal practice not to project hidden features or other features that

are not part of the inclined surface. When only the details for the inclined surface are

projected and drawn in the auxiliary view, the view is called a partial auxiliary view.

Partial auxiliary views may show only pertinent features not described by true projection in

the principal or other views, as shown in figure 5.13. They are used instead of complete

views to simplify the drawing. A partial view saves time and produces a drawing that is

more readable. Symmetrical objects can be represented as a half auxiliary view, that

is, only half of the object is drawn, as shown in figure 5.14. A complete (full) auxiliary

view is an auxiliary view that projects the whole object, including features that are not the

part of the inclined surface (surface of interest). A complete auxiliary view is harder to

draw, read and visualize. See the comparison of complete & partial views in figure 5.15.

When a cylindrical part is cut by an inclined plane, the resulting surface is an ellipse and

can only be shown true size and shape with an auxiliary view.

Figure 5.13 Partial auxiliary views

Figure 5.14 Half auxiliary views




Figure 5.15 Comparison of complete and partial auxiliary view

5.4 Applications of Auxiliary View

Auxiliary views are used to show the true shape/size of a feature, or the relationship of

part features that are not parallel to any of the principal planes of projection. The basic

method of multiview drawing is adequate to draw parts composed of horizontal and

vertical surfaces and for parts with simple inclined features. However, many parts have

inclined surfaces and features that cannot be adequately displayed and described by

using principal views alone. To provide a clear description of these features, it is

necessary to draw a view that will show them true shape/size.

Besides showing features true size, auxiliary views are used to dimension features that

are distorted in principal views and to solve graphically a variety of engineering problems.

The applications of auxiliary views can be grouped into the following five areas:

Reverse construction

True length of a line

Point view of a line

Edge view of a plane

True size of a plane




5.4.1 Reverse construction

For some objects, an auxiliary view must be created before a principal view can be drawn,

using a technique called reverse construction. For example, in figure 5.16, first the

auxiliary view is drawn first from front view and points established on the curves and then

projected back to draw right side view.

Figure 5.16 Reverse construction

5.4.2 True length of a line

A line appears in true length in a plane of projection parallel to it. To determine true length

of a line, make the folding line parallel to the line of interest, as shown in figure 5.17.

Figure 5.17 True length of a line




5.4.3 Point view of a line

A line will appear as a point view when projected onto a plane perpendicular to it. To show

a point view, choose the line of sight parallel to the line where it appears in true length as

shown in figure 5.19.

Figure 5.18 Point view of a line

One of the principal uses of auxiliary views is to show dihedral angle in true size, mainly

for dimensioning purpose by using point view of a line. Dihedral angle is the angle

between two planes. For example, the true dihedral angle, shown in figure 5.19, does not

appear because the direction of sight is not parallel to the line of intersection 1-2. In the

figure, the line of intersection 1-2 does not appear as a point in the front view; hence,

planes A and B do not appear as lines, and the true dihedral angle is not shown.




To get a view showing a true dihedral angle, shown in figure 5.19, first assume the

direction of sight parallel to the line of intersection 1-2 and draw line of projection so that

line 1-2 appears as a point(step 1), the draw auxiliary folding line perpendicular to

projection lines(step 2) and finally, complete the auxiliary view that shows the true

dihedral angle by transferring points(distances) from front view(step 3). Note that line 1-2

projected as a point 2,1 in the auxiliary view (application of point view of a line).

Figure 5.19 Dihedral angle




5.4.4 Edge view of a plane

Edge view of a plane appears in auxiliary view projected parallel to a true length line. A

plane will show on edge in a plane of projection which shows any line that lies entirely

within the plane as a point view. To get edge view of a plane, choose the direction of sight

parallel to a true length line lying in the plane, as shown in figure 5. 20.

Figure 5.20 Edge view of a plane




5.4.5 True size of a plane

True size of a plane appears in auxiliary view projected perpendicular to the edge view or

a plane shows true size when projected in a plane parallel to it. To get the true size of a

surface, choose the direction of sight perpendicular to edge view the plane as shown in

the figure 5.21.

Figure 5.21 True size of a plane