Technical Drawing and Sketching, Continued
Sketching arcs, circles, and ellipses are very similar processes. Lightly
drawing a box to the proportion of the desired arc, circle, or ellipse will help
in its construction. Using combined movements of your wrist and fingers,
make short counterclockwise strokes. When you must join arcs to straight
lines, draw the straight lines first to locate the ends of the arcs.
Figure 4-6 illustrates the sketching of arcs and circles within a box.
Figure 4-6.Sketching arcs
You may also draw circles and ellipses using a trammel. A trammel is a
length of cardboard or paper marked with both the major and minor axis of
the desired ellipse. Place the trammel so that two of the points are on the
respective axes. Mark the third point clearly since this point will form the
curve on the paper. Place a dot periodically at the third point as you move
the other two points along the axes. Place enough points to ensure a smooth
and symmetrical ellipse. Sketch the ellipse lightly, then follow more heavily
with the aid of irregular curves.
Figure 4-7 shows the use of a trammel.
Figure 4-7.Using a trammel to form a
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