Parallel PracticesIntroductionDrawing practices for parallel projections are more standardized than forperspective projections. There is very little latitude for creativeinterpretation of an object and more use of drawing and drafting instruments.Parallel projections are working drawings or blueprints.MechanicalconstructionScaleUse a scale, straightedge, triangles, and templates to mechanically constructaccurate parallel projections.Select a scale or ratio to represent the object on paper. Modify eachmeasurement you make with the selected scale. Make note of the scale youselect to enter in the appropriate space in the title block of the drawing.LayoutAll elements combined in a parallel projection drawing should present abalanced appearance. If you elect to draw your projection on standarddrawing paper with preprinted information blocks and borders, consider theplacement of views and the proximity of the information blocks. Make surethe drawing doesn’t overcrowd or interfere with information blocks. Do notarbitrarily alter the relationship of adjacent views on the paper because youincorrectly spaced the views.MeasurementsAll lines parallel to the picture plane project in true size or full scale. Alllines perpendicular to the plane of projection project as a point.Oblique orinclined lines are foreshortened. Use offset measurements to locate surfacecharacteristic that share common edges.Circles, arcs,and ellipsesCircles, arcs, and ellipses parallel to the plane of projection appear in truesize and shape. Circles not parallel to the plane of projection appear asellipses. Use the system of plotted points or circumscribed circle method ofprojecting circles, arcs, and ellipses on surfaces not parallel to the plane ofprojection since these curves have no direct transferable measurements.Reflections,Parallel projections generally do not contain reflections, shadows, andshadows, andshading since this would interfere with any textural implications made byshadecrosshatching, stipple, or other pattern.Continued on next page6-39
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