oblique projection chapter 15. 2 technical drawing 13 th edition giesecke, mitchell, spencer, hill...
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2Technical Drawing 13th EditionGiesecke, Mitchell, Spencer, Hill Dygdon, Novak, Lockhart
© 2009 Pearson Education, Upper Saddle River, NJ 07458.
All Rights Reserved.
Objectives
• Create an oblique projection• List the advantages and
disadvantages of oblique projection
• Draw cavalier and cabinet oblique drawings
3Technical Drawing 13th EditionGiesecke, Mitchell, Spencer, Hill Dygdon, Novak, Lockhart
© 2009 Pearson Education, Upper Saddle River, NJ 07458.
All Rights Reserved.
Objectives (cont.)
• Select the best view for circular shapes in an oblique drawing
• Describe why CAD software does not automatically create oblique drawings
4Technical Drawing 13th EditionGiesecke, Mitchell, Spencer, Hill Dygdon, Novak, Lockhart
© 2009 Pearson Education, Upper Saddle River, NJ 07458.
All Rights Reserved.
Oblique Projections
• In oblique projections, the projectors are parallel to each other but are not perpendicular to the plane of projection
• One of the object’s principal faces is parallel to the plane of projection
5Technical Drawing 13th EditionGiesecke, Mitchell, Spencer, Hill Dygdon, Novak, Lockhart
© 2009 Pearson Education, Upper Saddle River, NJ 07458.
All Rights Reserved.
Oblique Projections
6Technical Drawing 13th EditionGiesecke, Mitchell, Spencer, Hill Dygdon, Novak, Lockhart
© 2009 Pearson Education, Upper Saddle River, NJ 07458.
All Rights Reserved.
Cavalier Projection
• When the receding lines are true length, and the projectors are at 45 degrees to the plane of projection, the oblique drawing is called cavalier projection
7Technical Drawing 13th EditionGiesecke, Mitchell, Spencer, Hill Dygdon, Novak, Lockhart
© 2009 Pearson Education, Upper Saddle River, NJ 07458.
All Rights Reserved.
Cabinet Projection
• When the receding lines are drawn to half size, the drawing is known as a cabinet projection
8Technical Drawing 13th EditionGiesecke, Mitchell, Spencer, Hill Dygdon, Novak, Lockhart
© 2009 Pearson Education, Upper Saddle River, NJ 07458.
All Rights Reserved.
Cavalier and Cabinet Projection
9Technical Drawing 13th EditionGiesecke, Mitchell, Spencer, Hill Dygdon, Novak, Lockhart
© 2009 Pearson Education, Upper Saddle River, NJ 07458.
All Rights Reserved.
Choice of Position
• Important shapes should be parallel to the viewing plane
10Technical Drawing 13th EditionGiesecke, Mitchell, Spencer, Hill Dygdon, Novak, Lockhart
© 2009 Pearson Education, Upper Saddle River, NJ 07458.
All Rights Reserved.
Ellipses for Oblique Drawings• If using a CAD system, you can
draw an ellipse by specifying its center and major and minor axes
• If sketching, you can block in the enclosing rectangle and sketch the ellipse tangent to its sides
11Technical Drawing 13th EditionGiesecke, Mitchell, Spencer, Hill Dygdon, Novak, Lockhart
© 2009 Pearson Education, Upper Saddle River, NJ 07458.
All Rights Reserved.
Offset Measurements
• Circles, circular arcs, and other curved surfaces are drawn using offset measurements
12Technical Drawing 13th EditionGiesecke, Mitchell, Spencer, Hill Dygdon, Novak, Lockhart
© 2009 Pearson Education, Upper Saddle River, NJ 07458.
All Rights Reserved.
Angles in Oblique Projection• When an angle is specified in
degrees in a receding plane, convert the angle into linear measurements to draw the angle in an oblique drawing
13Technical Drawing 13th EditionGiesecke, Mitchell, Spencer, Hill Dygdon, Novak, Lockhart
© 2009 Pearson Education, Upper Saddle River, NJ 07458.
All Rights Reserved.
Angles in Oblique Projection
14Technical Drawing 13th EditionGiesecke, Mitchell, Spencer, Hill Dygdon, Novak, Lockhart
© 2009 Pearson Education, Upper Saddle River, NJ 07458.
All Rights Reserved.
Oblique Sections
• Sections are useful to show interior shapes
• In general, all types of sections for isometric drawing may be applied to oblique drawing
15Technical Drawing 13th EditionGiesecke, Mitchell, Spencer, Hill Dygdon, Novak, Lockhart
© 2009 Pearson Education, Upper Saddle River, NJ 07458.
All Rights Reserved.
Screw Threads in Oblique
• Partial circles spaced equally show symbolic thread pitch
16Technical Drawing 13th EditionGiesecke, Mitchell, Spencer, Hill Dygdon, Novak, Lockhart
© 2009 Pearson Education, Upper Saddle River, NJ 07458.
All Rights Reserved.
Oblique Dimensioning
• Oblique drawings are dimensioned in a similar fashion as isometric drawings
17Technical Drawing 13th EditionGiesecke, Mitchell, Spencer, Hill Dygdon, Novak, Lockhart
© 2009 Pearson Education, Upper Saddle River, NJ 07458.
All Rights Reserved.
Computer Graphics
• Using CAD, oblique drawings can be created by using snap increments and drawing similarly to drawing on grid paper
• If a complicated pictorial is needed however, it may be easier and more accurate to create a 3D model
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