Oblique Projection

Chapter 15

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.

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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.

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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