Orthographic Projections, Continued
Angles
Angles project in true size only when the plane of the angle is parallel to the
plane of projection. Since the surfaces of an object are inclined toward the
plane of projection, most angles will not project in true size. An angle may
project larger or smaller than true size depending on its position to the plane
of projection. Convert angular measurements into linear measurements
before laying them out along isometric lines. You may also use an isometric
protractor.
Sections
You may use all types of sectional views in isometric drawings and
projections. Half sections are used most often because only a quarter of the
object is removed, showing the relationship between the interior and exterior
surfaces. When drawing a half section in isometric, draw the entire object
first, then remove the half section. When drawing a full section where the
cutting plane passes completely through the object in an isometric drawing,
draw the cutting plane first, then draw the portion of the drawing behind the
cutting plane.
Figure 6-19 shows a half and full section in isometric.
Figure 6-19.—A half and full section in isometric.
Continued on next page
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