Parallel Practices
Introduction
Drawing practices for parallel projections are more standardized than for
perspective projections. There is very little latitude for creative
interpretation of an object and more use of drawing and drafting instruments.
Parallel projections are working drawings or blueprints.
Mechanical
construction
Scale
Use a scale, straightedge, triangles, and templates to mechanically construct
accurate parallel projections.
Select a scale or ratio to represent the object on paper. Modify each
measurement you make with the selected scale. Make note of the scale you
select to enter in the appropriate space in the title block of the drawing.
Layout
All elements combined in a parallel projection drawing should present a
balanced appearance. If you elect to draw your projection on standard
drawing paper with preprinted information blocks and borders, consider the
placement of views and the proximity of the information blocks. Make sure
the drawing doesn’t overcrowd or interfere with information blocks. Do not
arbitrarily alter the relationship of adjacent views on the paper because you
incorrectly spaced the views.
Measurements
All lines parallel to the picture plane project in true size or full scale. All
lines perpendicular to the plane of projection project as a point.
Oblique or
inclined lines are foreshortened. Use offset measurements to locate surface
characteristic that share common edges.
Circles, arcs,
and ellipses
Circles, arcs, and ellipses parallel to the plane of projection appear in true
size and shape. Circles not parallel to the plane of projection appear as
ellipses. Use the system of plotted points or circumscribed circle method of
projecting circles, arcs, and ellipses on surfaces not parallel to the plane of
projection since these curves have no direct transferable measurements.
Reflections,
Parallel projections generally do not contain reflections, shadows, and
shadows, and
shading since this would interfere with any textural implications made by
shade
crosshatching, stipple, or other pattern.
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