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THIRD-ANGLE PROJECTION

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Figure 5-5.-Elample  of a first-angle projection. Figure 5-6.-Firsl-angle projection brought into a single plane. shown in figure 5-5. The cube is supposed to be fronting toward the vertical plane of projection. As  you  can  see,  you  get  a  front  view  on  the vertical plane, a left side view on the profile plane, and  a  top  view  on  the  horizontal  plane. Now, to put these views on a sheet of drafting paper, you must get them all into the same plane. You presume that the vertical plane of projection is already in the plane of the paper. To get the other two views into the same plane, you rotate the   profile   plane   counterclockwise   and   the horizontal  plane  clockwise.  The  projection  now appears  as  shown  in  figure  5-6. This  first-angle  projection  arrangement of   views   is   considered   satisfactory   in   most European  drafting  practice.  In  the  United States,   it   is   considered   illogical   because   the top  view  is  below  the  front  view;  because the   right   side   of   the   object,   as   shown   in the  front  view,  is  toward  the  left  side  view of   the   object;    and  because  the  bottom  of the   object, as   shown   in   the   front   view, is  toward  the  top  view  of  the  object.  For these and other reasons, first-angle projection is not used much in the United States. THIRD-ANGLE   PROJECTION.—   Figure 5-7 shows a third-angle projection of a cube. As you can see, you get a front view on the vertical plane, a top view on the horizontal plane, and a right  side  view  on  the  profile  plane. Figure 5-7.-Example of a third-angle projection. 5-4



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