measuring distances along normal lines on the
multi-view projection and laying them off along
the corresponding isometric lines on the isometric
drawing. The angle that measures 40 degrees on
the top multi-view view measures only about
32 degrees on the isometric drawing. Note,
however, that it is labeled 40 degrees on the
isometric drawing. This is because it actually is
a 40-degree angle as it would look on a surface
plane at the isometric angle of inclination.
Circles in Isometric.— A circle in a normal multi-
view view will appear as an ellipse in an isometric
drawing. This is shown in figure 5-42, view A.
A procedure that maybe used to construct an
isometric circle is shown in figure 5-42, view B.
The steps of that procedure are as follows:
1. Draw the isometric center lines of the
circle. Then, using those center lines, lay off an
isometric square with sides equal to the diameter
of the circle.
2. From the near corners of the box, draw
bisectors to the opposite intersections of the center
lines and the box. The bisectors will intersect at
four points (A, A´, B, B´), which will be the
centers of four circular arcs.
3. Draw two large arcs with radius R, using
Points A and A´ as centers, Draw the two smaller
arcs with radius r, using Points B and B´ as centers.
If the above discussion seems familiar, it
should. It is simply an approximation of the four-
point method you studied in the previous chapter.
However, it can be used only when drawing
isometric circles on an isometric drawing.
Noncircular Curves in Isometric.— A line that
appears as a noncircular curve in a normal multi-
view view of an object appears as a non-isometric
Figure 5-43.-Method of drawing a noncircular curve in
isometric.
line in an isometric drawing. To transfer such a
line to an isometric drawing, you must plot a
series of points by measuring along normal lines
in the multi-view view and transferring these
measurements to corresponding isometric lines in
the isometric drawing.
The upperpart of figure 5-43 shows a two-
view multi-view projection of a block with
Figure 5-42.-A circle on a normal multi-view view appears as an ellipse in an isometric drawing.
5-23
