198 Section 2 Drafting Techniques and Skills
3. Enter the
Circle
command and draw a
circle using the center of the given circle
as the center point and a radius of R + r
(where r is the radius of the given circle).
4. The intersection of the two new circles
is the center of the required circle or arc.
Refer to Figure 6-49C.
Construct a
Circle or Arc
of a Given Radius Through
a Point and Tangent to a
Circle
CAD
Using a Compass
(Manual Procedure)
1. Point P, Circle O, and Radius R are given,
Figure 6-49A.
2. With a compass, strike Arc A with
Radius R and Point P as the center,
Figure 6-49B.
3. Strike Arc B using the center of the circle
as the arc center and a radius of R + r
(where r is the radius of the given circle).
4. The intersection of Arcs A and B is
the center of the required circle or arc,
Figure 6-49C.
An application of this construction is shown
in Figure 6-49D.
Using the Circle Command
(CAD Procedure)
1. Point P, Circle O, and Radius R are given.
Refer to Figure 6-49A.
2. Enter the
Circle
command and draw a
circle with Radius R using Point P as the
center. Refer to Figure 6-49B.
Figure 6-49. Constructing a circle or an arc of a given radius through a point and tangent to a circle. This
construction can be used for many different applications in drafting.
O
P
R
A B C D
r
R
P
A
B
R
R
R
R
R
Application
r
O
Construct a
Circle or Arc
of a Given Radius Tangent
to Two Given Circles
CAD
Using a Compass
(Manual Procedure)
1. Circle A, Circle B, and Radius R are
given, Figure 6-50A.
2. With Point A as a center and a radius
of R + ra (where ra is the radius of Circle A),
use a compass to strike Arc C, Figure 6-50B.
3. With Point B as a center and a radius of
R + rb (where rb is the radius of Circle B),
strike Arc D.
4. The intersection of Arcs C and D is the
center of the required tangent circle or
arc, Figure 6-50C.
An application of this construction is shown
in Figure 6-50D.