Chapter 6 Basic Geometric Constructions 201
snap and select the second line as the second
point on the diameter. The tangent circle is
drawn automatically.
You can also use the
Arc
command for
this construction if you are drawing a tangent
arc. This command provides a number of
ways to draw arcs. The
Three Points
option is
the default option. This option requires you to
specify a start point, a second point, and an
endpoint. You can also specify a center point,
a radius, a chord length, or other criteria when
drawing arcs. The following procedure uses
the
Start, End, Radius
option to draw an arc
tangent to two parallel lines.
1. Two parallel lines, Line AB and Line CD,
are given. Refer to Figure 6-52A.
2. Enter the
Arc
command and enter the
Start, End, Radius
option. With this
option, arcs are drawn counterclockwise.
3. To specify the start point, enter the
Midpoint object snap and select the
midpoint of Line AB.
4. Enter the
End
option. Enter the Perpen-
dicular object snap and select Line CD.
5. Enter the
Radius
option. To specify the
radius, enter the Mid Between Points
object snap. For the first point, enter the fi
Midpoint object snap and select Line CD.
For the second point, enter the Perpen-
dicular object snap and select Line AB.
This draws the required tangent arc.
Refer to Figure 6-52C.
Construct a
Circle or Arc
Tangent to Two Parallel
Lines
CAD
Using a Compass
(Manual Procedure)
1. Two parallel lines, Line AB and Line CD,
are given, Figure 6-52A.
2. Construct a parallel line, Line EF,
equidistant between Lines AB and CD,
Figure 6-52B.
3. The distance from Line AB (or Line CD)
to Line EF is the radius of the tangent
circle or arc. Set the compass to the
radius. Place the compass on Line EF
and strike the required circle or arc,
Figure 6-52C.
An application of this construction is shown
in Figure 6-52D.
Using the Circle or Arc Command
(CAD Procedure)
The
Two Points
option of the
Circle
com-
mand can be used to draw a circle that is
tangent to two parallel lines. After entering
this option, enter the Midpoint object snap
and select the fi rst line as the first fi point on the fi
diameter. Then, enter the Perpendicular object
Figure 6-52. Constructing a circle or an arc that is tangent to two parallel lines. A drafter will fi nd this construction
useful in many situations.
A B
A B C D
C D
A B
E
Equal
F
C D
Application