CHAPTER
10
Spatial Skills The art of blueprint reading is the ability to visualize a three dimensional object from lines on a plane surface.
Without this ability, the lines on a print are without meaning since they do in fact represent a three
dimensional object.
Prints and sketches are the plans that a tradesperson is required to use in their everyday assignments. It is
therefote necessary to sharpen, spatial skills in order to correctly read blueprints.
Orthographic Projection
The term orthographic projection is one used to describe the most common method of drawing views of an
object on a print. This method is one which incorporated views taken 90° trom the adjacent views. In
orthographic projection there are six main points to view, namely: front. top, bottom. back. right side. and
left side.
It is not necessary to draw all six views of an object to adequately describe its shal'e. However, it it always
necessary to draw at least two views to show the length, width, and depth. As the object .in question becomes
more complicated, more views become necessary. Most objects require three views to be completely described.
Consider a rectangular box:
The same rectangular box can have its sides labeled as follows:
Top
Left
Side
Right
Side
Chapter 10 -
Spatial Skills -
135
1
As it sets, aU sides are seen in their true size and shape. The top and right side appear on this paper as
parallelograms. In fact, the back, left side, and bottom views are not visible at all.
The principle of orthographic projection is to take these six views of the object and put them on one plane in
proper relationships to one another. This relationship can best be described by unfolding the surfaces of this
solid until they lie on one plane.
~-----Top-------,," I
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Front
~----------------
1. Unfold top and bottom so
they are in the same plane
as the front
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Front
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2. Unfold right side so that it is in
the same plane as the front.
3. Unfold left side and back together
to the plane of the front.
If these views of this object were to be placed on a print, they would appear as follows:
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136 -
Spatial Skills -
Chapter 10
D
Unfortunately, all objects that are-drawn on prints are not as simple as the one we have just shown. It becomes
necessary to use this idea of the rectangular box to show how orthographic projection works on other objects.
Take the following object as an example:
It becomes necessary to visualize this object inside a box.
As the object is viewed from each side, the lines visible are projected to the side of the box. The projection of
the front view would be accomplished as follows.
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If all the object lines (lines showing all visible edges in a view) were projected to the front surface, the front view
of an orthographic projection is seen.
In the same way, the top and right views can be done by viewing the object from the top and right sides and
projecting all visible edges to the plane of the box. With these three projections made, the box would look
as follows:
Chapter 10 -
Spatial Skills -
137
EXAMPLE 1:
An orthographic drawing is a method used to draw a 3-dimensional object on a 2-dimensional sheet of paper.
The orthographic drawing can be visualized by unfolding the box created previously and laJjf1g it out flat to
show the Front, Top, Right, Back, Left. and Bottom views of the object. The dotted lines indicaT'e hidden lines,
or lines not visable from that point of the view. The dashed lines are projection lines used by the draftsperson
to line up the views of the object (in this case the Right and Top views). Typically the projection lines are not
shown on the final drawing.
Projection Lines
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Hidden lines
Back Left
/
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Front
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Right
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Bottom
Only 3 views are necessary to give a clear idea of the 3-dimensional object being represented in the
orthographic drawing. Standard practice is to use the Front. Top. and Right side views of the object. The Front
view is the first view drawn and is used as the guide for the Top and Right side views. The draftsperson decides
which side of the object is to be called the Front view (typically it is the side showing the most detail or the
most complicated side) from which all other views are based.
Top
Right
- Chapter 10
EXAMPLE 2:
One view alone does not give enough information to accurately predict what the object will look like in
3-dimensions. In the examples below the front view by itself does not give the viewer a true perspective of the
object, additional information is needed. The front view shows the height and width of the object but does NOT
indicate the depth (thickness) of the object. Also, the front view does not tell us if surfaces A, B, C, and 0
protrude or recede. And if surfaces A, B, C, and 0 protrude then how far? There is just not enough information
given in one view alone.
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A
Surface
C
Surface
B
Surface
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Front
Using projection lines to align the features from the front view to the top view, let's see if the two views (front
and top) in the drawing below give enough information to visualize the object.
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Top
Front
The top view in the drawing above gives the third dimension depth, and the hidden lines are helpful in
visualizing the surfaces A, B. C, and 0 but more information is needed. Let's include the right side view using
projection lines to transfer features from the top view to the right view.
,-----,-
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- - - - -
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1
1
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With projection lines
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Top
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Front
Right
Without projection lines
With all three views the viewer has the information needed to visualize the object in 3-dimensions.
Chapter 10 -
Spatial Skills -
139
continued
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Chapter 10 - Spatial Skills -141
EXERCISE 2
Still another problem that develops is one which requires the drawing of three views of an object from the object
itself or a pictorial representation.
In the following exercise, pick as the front view the one that best shows the shape of the part. The other two views
picked will be the top and right side. Draw a sketch of each of the three views on a separate sheet of paper.
1.
2.
3.
4.
5.
6.
142 -
Spatial Skills -
Chapter 10
EXERCISE 3 In the following problems, one or more lines have been omitted. Complete each sketch with the necessary lines.
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Chapter 10
Spatial Skills -143
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EXERCISE 4
Instructions: Make a three view orthographic drawing
of the object shown. Each square represents %".
FRONT VIEW
TOP VIEW
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144 - Spatial Skills
FRONT VIEW
Chapter 10
RIGHT SIDE VIEW
EXERCISE 5
Identification of Numbered Points
Place the appropriate numbers in the circles on the orthographic drawings.
6-12
1-9
3
2-7
8-10
4
5-11
4-3
5-6
2-1
8-7
2-3
7
4-18 1310
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1-6
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11-12
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9-12
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19-22
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17-18
25-26-13-14
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Chapter 10 -
Spatial Skills -
145
d'.
EXERCISE 6
Surface Identification
Place letters in the circles attached to the surfaces of the picture to correspond to the letters attached to
the views.
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146 -
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Spatial Skills -
Chapter 10
,...,
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TIMED TEST Time - 6 Minutes
Circle the letter of the drawing which best matches the pieces in the numbered square.
A
B
C
B
C
D
E
D
E
A
B
B
C
D
D
E
Chapter 10 -
Spatial Skills -
147
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Sp at'lal Skills
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Chapter 10 -
Spatial Skills
149 F
Rotated/Flipped & Same Object/Different Object
Part Y. Rotated/Flipped - The first object in the row is to be compared with the five numbered objects in the
same row. Each numbered object is one question on the test. There are only two answer possibilities:
answer a. if the numbered object is a rotated (up to 360 degrees rotation) version of the first
unnumbered object in the row.
answer b. if the numbered object is flipped over (and could also be rotated) version of the first
unnumbered object in the row.
EXAMPLE 1:
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answers:
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4a
3b
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Part Z. Same ObjecVDifferent Object - The first unnumbered object in the row is to be compared with the five
numbered objects which follow in the row. Each numbered object is one test question. There are only
two possible answer choices:
answer a. if the numbered object is the same object as the first unnumbered object in the row. The
object may be rotated.
answer b. if the numbered object is a different object when compared to the first unnumbered object
in the row.
EXAMPLE 2:
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2
1
answers:
150
1b
Spatial Skills -
2a
Chapter 10
3b
4a
5b
3
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FORMYANDZ
TIMED TEST - 12 Minutes for Forms Y & Z
Form Y For each object answer either, "An if rotated or "B" if flipped over.
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Chapter 10 -
Spatial Skills -151
Form Y For each object answer either, "A" if rotated or "8" if flipped over.
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Form Z
For each object answer either, "A" for same object or "8" if a different object.
2
3
4
5
6
7
8
9
10 11
12 18 19
20
28
29
30 o
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17
21
22 26
27
Chapter 10
Spatial Skills
153 ~.<:l';'
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Form Z
For each object answer either, "A" for same object or "8" if a different object.
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32
33
34
35
36
37
38
39
40 41
42
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154 ­
Spatial Skills ­
43
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49
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52
53
56
57
58
Chapter 10
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55
59
60
Cube Unfolding & Cube Folding Test
Time allowed is 14 minutes to complete parts A, B, C, and D of the test. Dotted lines indicate fold lines.
Part A.
Cube Unfolding
The first numbered cube in the row is folded. Compare it to the four lettered unfolded cubes in the
row. Circle the letter of the unfolded cube which matches the numbered cube.
..
M
EXAMPLE 1:
Part B.
Cube Folding
The first numbered cube in the row is unfolded. The four folded cubes which follow in the row are
lettered. Circle the letter of the folded cube which corresponds to the numbered cube.
A
EXAMPLE 2:
Answers:
Example 1 = D
Example 2
=
B
C
D
B
Hint 1: Note where the point of a triangle lines up with the shape in the adjacent side, and where the base of
a triangle lines up.
Hint 2: Note where a solid line meets the shapes in adjacent sides.
Hint 3: Note letter or number orientation.
Hint 4: Concentrate only on the visible faces of the cubes, don't be concerned with what may be on the non­
visible faces.
Chapter 10 "- Spatia! Skills
155
Part A Directions· Circle the letter for the object that best matches the assembled cube.
,
2
A
3
A
B
B
4
5
6
-----
....~--------------------------
156 -
Spatial Skills -
Chapter 10
Part B Directions - Circle the letter for the object that best matches the unfolded cube.
A
B
C
o
8
A
B
C
o
9
A
B
C
o
10
A
B
C
o
11
A
B
C
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Chapter 10 -
Spatial Skills -
157
Part C Directions - Circle the letter for the object that best matches the assembled cube.
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158 ­ Spatial Skills ­ Chapter 10
B
D
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Part D Directions - Circle the letter for the object that best matches the unfolded cube.
18
A
B
C
D
19
A
B
C
D
20
A
B
C
D
21
A
B
C
D
22
A
B
C
D
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Chapter 10 -
Spatial Skills -
159