A REVIEW OF ORTHOGRAPHIC PROJECTION

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LESSON 13 A REVIEW OF ORTHOGRAPHIC
PROJECTION What is drafting? As explained in a
previous lesson Drafting is a Graphic Language
that uses Lines, Symbols and Words to describe
any object that may be manufactured or
constructed. Often referred to as The Language
of Industry and having its own Alphabet in form
of lines and using established Methods of
graphically displaying two dimensional and three
dimensional objects The Language of Industry is
the most important tool designers and draftsmen
have to convey ideas to others.
What is Orthographic Projection? Orthographic
Projection is the accepted method used world wide
in engineering classes such as Technical Drawing
and in industry to display any object as a series
of projected views. Most frequently these views
are the Top, Front, and Right Side.
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How are edges shown in Orthographic
Projection? The outside edges of an object are
shown using solid lines called Object Lines or
Visible Object Lines through out the views of the
object. When an edge of a design detail is not
able to be seen in the views then the edge is
shown using an Invisible Line or Hidden Line. A
hidden line is a line drawn with a series of
dashes equal in length and spacing. example A
square containing a hole through its length and
centered on the surface of the square will in the
TOP view display object lines representing the
four sides of the square and a solid circle
representing the hole. In the FRONT view the
outside edges will be shown as solid object lines
and the edges of the circle will be projected as
HIDDEN LINES since you are unable to see the
edges through the thickness of the square.
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A SIMPLE REMINDER The Autocad software provides
all of the Linetypes needed to technically draw
the views of objects. What does the term Detail
mean? A detail is defined as a drawing having
Several Views with Dimensions. The drawing can
be an isometric with in isometric dimensions or
one, two or three orthographic views with
dimensions throughout the views. A detail in
Cad Class describes any of the problems contained
within the class workbooks and hand out
sheets. As you look through the CAD WORKBOOK in
class you will see many DETAILS (assignments
/problems) shown using several technical methods
of display. Some drawings contain only one
view, others are displayed with several views and
many are displayed as isometrics (picture like
form).
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After you complete this lesson please study the
different displayed details in the Class
Workbook. A good understanding of them will
help to improve your ability to READ technical
drawings. Take a close look at the very first
detail shown in isometric on page 19 of the
ASSEMBLY AND DETAILS portion of the CAD
Workbook. The L Block detail will be used as a
demo problem in The Orthographic Projection_
Presentation NOW OPEN The Orthographic
Projection_Presentation
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