Chapter 4
Sketching and
Orthographic Projection
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Links for Chapter 4
Sketching Shapes
Sketching Procedures
Orthographic Projection
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Sketching Tools & Materials
• Soft lead pencil with H or HB lead
• Type of paper is not critical as long as the idea can be conveyed
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Sketching Lines
• Create lines with short connected segments
• Keep lines light so they can easily be erased
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Sketching Circles• Trammel method
– Mark the radius of the circle on the trammel– Place pencil on one point while holding the
other point at the center of the circle– Rotate trammel around the center
• Hand compass method– Use your hand as the center and rotate paper
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Measurement and Proportion
• Proportion of lines to each other are more important then the size of the sketch itself
• The first line sketched determines the scale of the drawing
• Make sure the direction and position of lines are accurate
• Use your pencil to establish measurements
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Sketching Procedures
• Before sketching try to visualize the object
• Sketch very light lines of the outline
• Add details being careful to keep the proportion correct
• Darken in the desired lines of the final sketch
• Use a grid to create irregular shapes
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Multiview Sketches
• Block out views and 45° line
• The 45° line is used to project lines from the top and right side view
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Isometric Sketches
• Isometric sketches are a three-dimensional pictorial representation of the object
• Begin by drawing– Horizontal ground line
– Perpendicular line
– Two 30° lines
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Isometric Sketches
• Determine best view for the front
• Set up isometric axes
• Sketch overall block
• Add details
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Isometric Details
• Nonisometric lines are not parallel to one of the three original axes and are not true length
• Circles and arcs appear as ovals– Use the four-center method to construct
– Be sure they lie on the proper plane
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Orthographic Projection
• Any projection of features onto an imaginary perpendicular plane– Lines of sight are perpendicular to the plane
– Objects are true size if they are parallel to the plane
– Objects are foreshortened if they are not parallel to the plane
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Multiview Projection
• In architecture, two-dimensional exterior drawings are referred to as elevations
• Use a glass box to help visualize the six views
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Multiview Details
• Use the front, left side, right side, and back as elevations
• Top view is the roof plan
• Project circles and inclined lines using the 45° line projection method