sectional views - mechanical engineering · © 2011 pearson higher education, 2 upper saddle river,...
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C H A P T E R 62
Sectional Views
Engineering Graphics with AutoCAD 2011, 1/e James Bethune
© 2011 Pearson Higher Education, Upper Saddle River, NJ 07458. • All Rights Reserved. 2
Sectional views Sectional views are used in technical drawing to expose internal
surfaces. They serve to present additional orthographic views of surfaces
that appear as hidden lines in the standard front, top, and side
orthographic views.
Engineering Graphics with AutoCAD 2011, 1/e James Bethune
© 2011 Pearson Higher Education, Upper Saddle River, NJ 07458. • All Rights Reserved. 3
Hatch lines
Hatch lines are drawn on the surfaces that represent where the cutting
plane passed through solid material. Also shown are the front and right-
side orthographic views and a sectional view.
Engineering Graphics with AutoCAD 2011, 1/e James Bethune
© 2011 Pearson Higher Education, Upper Saddle River, NJ 07458. • All Rights Reserved. 4
CUTTING PLANE LINES
Cutting plane lines are used to define the location for the sectional
view’s cutting plane. An object is “cut” along a cutting plane line.
Engineering Graphics with AutoCAD 2011, 1/e James Bethune
© 2011 Pearson Higher Education, Upper Saddle River, NJ 07458. • All Rights Reserved. 5
SECTION LINES
Section lines are used to define areas that represent where solid
material has been cut in a sectional view. Section lines are evenly
spaced at any inclined angle that is not parallel to any existing edge line
and should be visually distinct from the continuous lines that define the
boundary of the sectional view.
If two or more parts are included within the
same sectional view, each part must have
visually different section lines.
Engineering Graphics with AutoCAD 2011, 1/e James Bethune
© 2011 Pearson Higher Education, Upper Saddle River, NJ 07458. • All Rights Reserved. 6
HATCH
Section lines are drawn in AutoCAD using the Hatch tool, located on the
Draw panel under the Home tab. The Hatch tool offers many different
hatch patterns and spacings. The general pattern of evenly spaced lines at
45° is defined as pattern ANSI31 and is the default setting for the Hatch tool.
Engineering Graphics with AutoCAD 2011, 1/e James Bethune
© 2011 Pearson Higher Education, Upper Saddle River, NJ 07458. • All Rights Reserved. 7
STYLES OF SECTION LINES
AutoCAD has more than 50 different hatch patterns. The
different patterns can be previewed in the Swatch option in the
Hatch Creation panels.
Engineering Graphics with AutoCAD 2011, 1/e James Bethune
© 2011 Pearson Higher Education, Upper Saddle River, NJ 07458. • All Rights Reserved. 8
SECTIONAL VIEW LOCATION Sectional views should be located on a drawing behind the
arrows. The arrows represent the viewing direction for the
sectional view
Engineering Graphics with AutoCAD 2011, 1/e James Bethune
© 2011 Pearson Higher Education, Upper Saddle River, NJ 07458. • All Rights Reserved. 9
HOLES IN SECTIONS
As with orthographic views, a conical point must be included on holes
that do not completely penetrate the object.
A common mistake is to omit the back edge
of a hole when drawing a sectional view.
Engineering Graphics with AutoCAD 2011, 1/e James Bethune
© 2011 Pearson Higher Education, Upper Saddle River, NJ 07458. • All Rights Reserved. 10
GRADIENTS
In AutoCAD a gradient is shading that varies in intensity.
Engineering Graphics with AutoCAD 2011, 1/e James Bethune
© 2011 Pearson Higher Education, Upper Saddle River, NJ 07458. • All Rights Reserved. 11
OFFSET SECTIONS
Cutting plane lines need not be drawn as straight lines across the
surface of an object. They may be stepped so more features can be
included in the sectional view.
Engineering Graphics with AutoCAD 2011, 1/e James Bethune
© 2011 Pearson Higher Education, Upper Saddle River, NJ 07458. • All Rights Reserved. 12
MULTIPLE SECTIONS
More than one sectional view may be taken off the same
orthographic view.
Engineering Graphics with AutoCAD 2011, 1/e James Bethune
© 2011 Pearson Higher Education, Upper Saddle River, NJ 07458. • All Rights Reserved. 13
ALIGNED SECTIONS
Cutting plane lines taken at angles on circular shapes
may be aligned.
Aligning the sectional views prevents the foreshortening that would result if
the view were projected from the original cutting plane line location. A
foreshortened view would not present an accurate picture of the object’s
surfaces.
Engineering Graphics with AutoCAD 2011, 1/e James Bethune
© 2011 Pearson Higher Education, Upper Saddle River, NJ 07458. • All Rights Reserved. 14
DRAWING CONVENTIONS IN
SECTIONS Slots and small holes that penetrate cylindrical surfaces may be drawn as
straight lines, as shown below. Larger holes, that is, holes whose
diameters are greater than the radii of their cylinders, should be drawn
showing an elliptical curvature.
Engineering Graphics with AutoCAD 2011, 1/e James Bethune
© 2011 Pearson Higher Education, Upper Saddle River, NJ 07458. • All Rights Reserved. 15
HALF, PARTIAL,AND
BROKEN-OUT SECTIONAL VIEWS
Half and partial sectional views allow a designer to show an
object using an orthographic view and a sectional view within one
view..
Engineering Graphics with AutoCAD 2011, 1/e James Bethune
© 2011 Pearson Higher Education, Upper Saddle River, NJ 07458. • All Rights Reserved. 16
REMOVED SECTIONAL VIEWS Removed sectional views are used to show how an object’s shape
changes over its length. Removed sectional views are most often used
with long objects whose shape changes continuously over its length.
Engineering Graphics with AutoCAD 2011, 1/e James Bethune
© 2011 Pearson Higher Education, Upper Saddle River, NJ 07458. • All Rights Reserved. 17
BREAKS It is often convenient to break long continuous shapes so that they
take up less drawing space. There are two drawing conventions used
to show breaks: freehand lines used for rectangular shapes, and S-
breaks used for cylindrical shapes.
Engineering Graphics with AutoCAD 2011, 1/e James Bethune
© 2011 Pearson Higher Education, Upper Saddle River, NJ 07458. • All Rights Reserved. 18
SECTIONAL VIEWS
OF CASTINGS Cast objects are usually designed to include a feature called a rib.
Ribs add strength and rigidity to an object. Sectional views of ribs
do not include complete section lines because this is considered
misleading to the reader.
Engineering Graphics with AutoCAD 2011, 1/e James Bethune
© 2011 Pearson Higher Education, Upper Saddle River, NJ 07458. • All Rights Reserved. 19
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