1. Drafting – Product Design & Architecture
Orthographic Projection

2. Alphabet of Lines Short Break Line: A freehand
drawn line that shows where a part is
broken to reveal detail behind the part or
to shorten a long continuous part. (See
example of Long Break Line
on the next slide.)
Object Line: Thick lines
about .6mm(.032in) that show
the visible edges of an object.
Hidden Line: Lines used to
show interior detail that is not visible
from the outside of the part.
Center Line: Lines that define
the center of arcs, circles, or symmetrical parts.
They are half as thick as an object line.
Section Lines: Lines are used to
define where there is material
after a part of the object is cut away.
Construction Line: Very lightly
drawn lines used as guides to help draw
all other lines and shapes properly.
Usually erased after being used.

3. Alphabet of Lines Long Break Lines: Break lines are used
to either show detail or as in this case they can
be used to shorten very long objects that
do not change in detail. Notice that this part
is 12” long however we have shortened
the drawing with break lines to use
our space more efficiently.
Dimension Lines: Lines that are used to
show distance. Arrows are drawn on the
ends to show where the dimension line starts and ends.
The actual distance is usually located in the middle of this
line to let you know the distance being communicated.
Dimension lines are used in conjunction
with extension lines to properly
dimension objects.
Cutting Plane Line: A line used to
designate where a part has been cut
away to see detail. The arrows should
point in the direction that you are
looking at the cutout.
Extension Lines: Lines used to show where
a dimension starts and stops on an object.
Used with dimension lines to properly dimension
an object. The line is 1/16” away from the
part as to not get confused with the object lines
Leader Lines: Leader lines are used to
show dimensions of arcs, circles and to help
show detail. An arrow head is used to point
to the part you are dimensioning and the line comes
off the arrow point usually at a 45 degree angle.
At the end of this line a horizontal line is drawn
with a note at the end telling information
about what is being pointed at.
How many lines from the
previous slide can you identify
here?

4. Alphabet of lines Phantom Lines: Phantom lines are used
to identify alternate positions that a part my
take up. In this example we are using Phantom
lines to show that the door handle may only move
45 degrees from it’s horizontal
position.
How many lines from the
previous 2 slides can you
identify here?

5. Orthographic (Multiview Drawings)
Pictorial sketches are great for engineers to explain ideas and communicate what the final part will look like to the customer. Unfortunately, pictorial drawings have some disadvantages. Foreshortened views and distorted features do not allow for accurate prototyping. Many times, for parts to be accurately depicted, you need straight on views of each surface.

6. Orthographic (Multiview Drawings)
In order to obtain these straight line views we have a type of drawing called Orthographic Projection also known as Multiview drawings. Orthographic projection is a way to project a view based on a line of sight that is perpendicular to that view. There are six of these views to any object as shown in the next slide.

7. Orthographic (Multiview Drawings)
The arrows represent the
line of sight associated
with each view.
Use the button
below to jump
between this
view and the ortho
view on the next
page.
ORTHO

8. Orthographic Principal Views
Note how the views
are oriented. Each view is
adjacent to the other as
if they were unfolded
from a 3D shape.
Front,
Top and Right views
are used most often. You can
see how other views resemble
these three except they are not
as clear due to hidden lines.
Click to go back
to ISO view.
ISO

9. Orthographic View Selection
Finding the best view of a part can be difficult. Two or more sides may look like the best solution for a front view. On the next slide is a list of characteristics that you should use in choosing your views.

10. Orthographic View Selection
Steps in selecting the front.
Most natural position or use.
Shows best shape and characteristic contours.
Longest dimensions.
Fewest hidden lines.
Most stable and natural position.
Relationship of other views
Most contours.
Longest side.
Least hidden lines.
Best natural position.

11. Orthographic View Selection
Most natural position.
Longest Dimension
Best shape description.
No hidden lines.

12. Orthographic View Selection Numbers
Another decision on view selection you need to make is how many views. You usually do not need more than three but you may only need one or two. The following slides will show when to make a decision between one, and two view drawings.

13. One View Selection Two views will be identical Uniform shape.
All dimensions easily
shown on one view.

14. One View Selection It is also possible to have one view drawings
of objects that are flat
and have even thickness.
Gauges and gaskets are
two such objects. We
have a gauge here on the
left.

15. Two View Selection Symmetrical parts. A third view
would be identical to the other
views
Second view is necessary for
depth.

16. Precedence of Lines
In multiple view drawings, many times different line types will take up the same space, therefore, we have line precedence. The following is an explanation of which lines exist over others.
Object lines over hidden and center.
Hidden over center.
Cutting plane lines over center lines.
The following slide will show an example.

17. Precedence of Lines An object line here takes precedence
over the center line. However we
draw short thin lines beyond the
object to show there is a center line
underneath the object line.
Object lines took precedence over
the hidden lines you would see
from the hole. The center line in
the top view would show the depth
of the hole as well as the right
side view.

18. Do you want to be a good sketcher?
Practice
First Slide

19. Multiview Drawing
Another name for orthographic projection is multiview drawing
Involves visualization and implementation
Ability to see clearly in the mind’s eye an object
Process of drawing the object

20. Multiview Drawing
A system that allows you to make a two-dimensional drawing of a three-dimensional object

21. Viewing Objects
A box is formed by six mutually perpendicular planes of projection that are located around the object

22. Viewing Objects
Lines are formed on the planes by projecting the edges of the object onto the planes
These images are called “views”
There are six views formed by the planes of a box

23. Viewing Objects
Unfolding the box produces an arrangement of the six views

24. Angles of Projection First-angle projection
Used by many European countries
Object is projected onto planes from the first angle or quadrant
Front view projected to vertical plane
Top view projected to horizontal plane
Left-side view projected to profile plane

25. Angles of Projection Third-angle projection
Standard for the United States
Third quadrant is used for projection
Front view projected to vertical plane
Top view projected to horizontal plane
Right-side view projected to profile plane

26. Viewing Objects
Each view is placed in a constant location relative to the other views
Each view must be placed in its correct position
Views and features must be aligned

27. Choosing Views Most commonly used views
Front View
Top View
Right Side View
Most descriptive view is typically designated as the Front View

28. Choosing Views
Complex objects require three views to describe its shape
Simple objects can be described with two views
Ex: Soda Can
Thin objects can be described with only one view
Depth is given in a note
Ex: Erasing Shield

29. Choosing the Views Objects described in two views
Third view would add nothing to the description of the object
Carefully select views to describe shape of objects accurately

30. Curved Surfaces
CYLINDER
CONE
Some curved surfaces do not show as curves in all views
WHEEL
FRUSTRUM

31. Object Dimensions All objects have 3 dimensions
Height
Distance from top to bottom
Width
Distance from side to side
Depth
Distance from the front to back

32. Object Dimensions Front View Top View Side View Shows width & height
Shows width & depth
Side View
Shows height & depth

33. Drawing Views of Objects
Depth can be projected between views by using a 45° miter line

34. Line Types - Visible
Edges that can be seen in a given view areVisible or Object lines
Visible lines are thick and dark
.028” or .7mm
F or HB lead

35. Line Types - Hidden
Edges that cannot be seen from a given view are indicated by Hidden lines

36. Line Types - Hidden Drawing hidden lines .125” (3mm) dashes
.0625” (1mm) spaces between dashes
Thin: .020” (.5mm)
Dark: F or HB lead

37. Line Types - Hidden Follow rules for hidden line placement
Alphabet of Lines
Drawings produced with CAD may violate hidden line rules

38. Line Types – Center
Center lines indicate axes of symmetry

39. Line Types – Center Perpendicular lines for circular objects
Small dashes cross at the center point of feature
One center line drawn to indicate longitudinal axis of cylinder or hole

40. Line Types - Center
Draw center lines using a series of long and short dashes
.125” (3mm) short the center
.75”- 1.5” (20mm-40mm) long dash
.0625” (1mm) spaces between dashes
Thin: .02” (5mm)
Long dash extends .125” to .25” beyond feature

41. Placement of Views
Views should be visually balanced within the working space

42. Steps for Centering a Drawing
Draw border and title block using light construction lines
Draw diagonal lines from corners of border

43. Steps for Centering a Drawing
Add:
Width 5.13
Space 1.50
Depth 2.00
Horizontal 8.63
Height 3.00
Space
Depth
Vertical 6.50

44. Steps for Centering a Drawing
Draw a box the size of all views
Measure from the center:
Half the width
Half the height

45. Steps for Centering a Drawing
Draw in views using light construction lines

46. Adding Details Add holes and features
Transfer horizontal and vertical features
Use miter line to transfer depth

47. Multiview Drawing

48. Straight Edges
Edges that are perpendicular to a plane of projection appear as a point 1 2 3

49. Straight Edges
Edges that are parallel to a plane of projection appear as lines
Edges that are inclined to a plane of projection appear as foreshortened lines

50. Curved Edges
Curved edges project as straight lines on the plane to which they are perpendicular
Curved edges project as curved lines on the planes to which they are parallel or inclined

51. Normal Surfaces
Normal surfaces appear as an edge in two opposite principal views, and appear a surface in all other principal views.

52. Inclined Surfaces
Inclined surfaces appear as an edge in two opposite principal views, and appear foreshortened (not true size) in all other principal views.

53. Oblique Surfaces
Oblique surfaces do not appear either as an edge or true size in any principal view.

54. Intersections & Tangencies
Where a curved surface is tangent to a plane surface, no line should be shown where they join

55. Intersections & Tangencies
Where a plane surface intersects a curved surface, an edge is formed

56. Intersections & Tangencies
Where the plane surface is horizontal or vertical, exceptions to these rules may occur