186 Section 2 Drafting Techniques and Skills
Construct an
Octagon Using the
Polygon Command
CAD
An octagon can be constructed in the same
manner as a hexagon by using the
Polygon
com-
mand. Instead of specifying six sides, specify
eightsides.Theoctagoncanbeconstructedbased
on the distance across the flats or the distance fl
across the corners. If the distance across the fl ats fl
is known, use the
Circumscribed
option. Refer to
Figure 6-33. If the distance across the corners
is known, use the
Inscribed
option. Refer to
Figure 6-34. As is the case with a hexagon, a
center point and radial distance are required
after entering the number of sides.
Note
In addition to squares, hexagons, and
octagons, you can construct other regular
polygons using the
Polygon
command. Simply
specify the number of sides after entering the
command. You can then specify a given side
length, a distance across the flats, or a distance fl
across the corners. Use the method that is most
appropriate for a given construction.
Figure 6-36. An inscribed regular polygon having any number of sides (seven in this case) can be constructed if
the diameter of the circle is given.
A
1 2 3 4 5 6 7 B
A
A
1 2 3 4 5 6 7 B
B
A
1 2 3 B
C
P P
C
1. Draw a circle with the given diameter.
Divide its diameter into the required
number of equal parts (seven in this
example), Figure 6-36A. Use the inclined
line method illustrated in Figure 6-8.
2. With a radius equal to the diameter
and with centers at the diameter ends
(Points A and B), draw arcs intersecting
at Point P, Figure 6-36B.
3. Draw a line from Point P through the
second division point of the diameter
(Line AB) until it intersects with the
circle at Point C, Figure 6-36C. The
second point will always be the point
used for this construction. Chord AC is
one side of the polygon.
4. Lay off the length of the first side around fi
the circle using dividers. This will
complete the regular polygon with the
required number of sides.
Construct an
Inscribed Regular
Polygon Having Any
Number of Sides with the
Diameter of the Circle Given