Chapter 6 Basic Geometric Constructions 197
Construct a
Circle or Arc
of a Given Radius Through
a Point and Tangent to a
Straight Line
CAD
Using a Compass
(Manual Procedure)
1. Point P, Line AB, and the Radius R are
given, Figure 6-48A.
2. With a compass, strike Arc C with
Radius R and Point P as the center,
Figure 6-48B.
3. At a distance from Line AB equal to
Radius R, draw Line DE parallel to
Line AB.
4. The intersection of Arc C and Line DE
is the center of the tangent circle or arc,
Figure 6-48C.
An application of this construction is shown
in Figure 6-48D.
Figure 6-48. Constructing a circle or an arc of a given radius through a point and tangent to a line. A drafter may
encounter many cases where this construction must be used.
R
P
A B
D
C
E
R
R
1 1/2
3/4
3/8
P
A
A B
B C D
A B
Application
(CAD Procedure)
1. Point P, Line AB, and Radius R are given.
Refer to Figure 6-48A.
2. Enter the
Circle
command and draw a
circle with Radius R using Point P as the
center. Refer to Figure 6-48B.
3. Enter the
Offset
command and offset
Line AB at a distance equal to Radius R.
4. The intersection of the circle and the
offset line is the center of the tangent
circle or arc. Refer to Figure 6-48C.