Drafting

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Drafting Product Design Architecture

• Orthographic Projection

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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.)
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.
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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?
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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 its horizontal position.
How many lines from the previous 2 slides can
you identify here?
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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.

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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.

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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
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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.
Click to go back to ISO view.
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.
ISO
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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.

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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.

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

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One View Selection
Two views will be identical
Uniform shape.
All dimensions easily shown on one view.
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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.
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Two View Selection
Symmetrical parts. A third view would be
identical to the other views
Second view is necessary for depth.
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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.

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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.
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Do you want to be a good sketcher?
First Slide
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Multiview Drawing

• Another name for orthographic projection is
  multiview drawing
• Involves visualization and implementation
• Ability to see clearly in the minds eye an
  object
• Process of drawing the object

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Multiview Drawing

• A system that allows you to make a
  two-dimensional drawing of a three-dimensional
  object

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Viewing Objects

• A box is formed by six mutually perpendicular
  planes of projection that are located around the
  object

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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

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Viewing Objects

• Unfolding the box produces an arrangement of the
  six views

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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

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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

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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

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Choosing Views

• Most commonly used views
• Front View
• Top View
• Right Side View
• Most descriptive view is typically designated as
  the Front View

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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

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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

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Curved Surfaces
CYLINDER
CONE

• Some curved surfaces do not show as curves in all
  views

FRUSTRUM
WHEEL
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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

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Object Dimensions

• Front View
• Shows width height
• Top View
• Shows width depth
• Side View
• Shows height depth

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Drawing Views of Objects

• Depth can be projected between views by using a
  45 miter line

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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

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Line Types - Hidden

• Edges that cannot be seen from a given view are
  indicated by Hidden lines

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Line Types - Hidden

• Drawing hidden lines
• .125 (3mm) dashes
• .0625 (1mm) spaces between dashes
• Thin .020 (.5mm)
• Dark F or HB lead

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Line Types - Hidden

• Follow rules for hidden line placement
• Alphabet of Lines
• Drawings produced with CAD may violate hidden
  line rules

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Line Types Center

• Center lines indicate axes of symmetry

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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

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Line Types - Center

• Draw center lines using a series of long and
  short dashes
• .125 (3mm) short dash _at_ 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

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Placement of Views

• Views should be visually balanced within the
  working space

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Steps for Centering a Drawing

• Draw border and title block using light
  construction lines
• Draw diagonal lines from corners of border

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Steps for Centering a Drawing

• Add
• Width 5.13
• Space 1.50
• Depth 2.00
• Horizontal 8.63
• Height 3.00
• Space 1.50
• Depth 2.00
• Vertical 6.50

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Steps for Centering a Drawing

• Draw a box the size of all views
• Measure from the center
• Half the width
• Half the height

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Steps for Centering a Drawing

• Draw in views using light construction lines

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Adding Details

• Add holes and features
• Transfer horizontal and vertical features
• Use miter line to transfer depth

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Multiview Drawing
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Straight Edges

• Edges that are perpendicular to a plane of
  projection appear as a point

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3
1
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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

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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

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Normal Surfaces

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

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Inclined Surfaces

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

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Oblique Surfaces

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

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Intersections Tangencies

• Where a curved surface is tangent to a plane
  surface, no line should be shown where they join

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Intersections Tangencies

• Where a plane surface intersects a curved
  surface, an edge is formed

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Intersections Tangencies

• Where the plane surface is horizontal or
  vertical, exceptions to these rules may occur