Technical Drawing Program
Engineering Graphics
GEOMETRIC CONSTRUCTIONS
Geometric constructions allow the architect, engineer, designer
or drafter to apply the principles of geometry in the creation
of accurate drawings of objects using only a compass to draw arcs
and a straight-edge to draw lines.
- Bisect a line - locates the midpoint of a line and creates
a perpendicular line at the midpoint of the line.

Given Line AB, draw two arcs (red) AC & BD (AC=BD)
and then draw a line (blue) at the points of intersection E & F.
- Bisect an arc - locates the midpoint of an arc and creates
a line that passes through the center of the arc.

Given Arc AB, draw two arcs (red) AC & BD (AC=BD)
and then draw a line (blue) at the points of intersection.
- Bisect an angle - divides an angle into two equal angles
and can be used to create 45° angled lines.

Given Angle ABC, draw an arc (red) at any radius
from the vertex at B, then draw two equal arcs
(blue) at the points of intersection
and then draw a line (green) from the vertex at B to the intersection of
the blue
arcs.
- Construct a perpendicular line from a point to a line -

Given Line AB and Point C, draw an arc
(red)
of any radius that intersects AB
at two points E & F; then draw two arcs (blue) EG & EF (EG=EF); and finally, draw a line (blue) at the
points of intersection G to point C. CG is now perpendicular
to AB.
- Construct a perpendicular line from a point on a line -

Given Line AB and Point C, draw an arc (red) of any radius
that intersects AB at two points D& E; then draw two arcs
(blue)
DF & EF (DF=EF); and finally, draw a line
(blue) at the point of intersection
F to point C. CF is now perpendicular to AB.
- Construct a perpendicular line from a point near the end
of a line -

Given Line AB and Point C, draw an arc (red) of any radius
that intersects AB at points C & D; then draw a line (blue) from point
D throught the center of the (red) arc until it intersects the arc again at E;
then draw a line (green) at the points
of intersection E to point C. CE is now perpendicular to AB.
- Construct a line parallel to a line from a point -

Given Line AB and Point C, draw an arc from Point C at any radius
(2.41) intersecting Line AB at Point
D. Repeat the (2.41) radius from Point D interssecting AB at Point
E. At Ponit E draw a radius from Point C (1,18) and repeat the (1.18) at Point D intersecting the (2.41) radius at Point F. Now, draw a line from Point
C to Point F.
- Construct a line parallel to a line at a fixed distance -

Given Line AB and a specific distance (ex.
1.18), draw two arcs (red)
at random points on Line AB; then draw a Line CD (blue)
that is tangenet to each arc.
- Construct a right triangle given one measurement -

Given a distance From Point A to Point 1, draw four (4) arcs
(red) equal to A1 to the right of
Point 1 along a horizontal line. Label each arc 2, 3, 4, &
5. Draw an additional arc (red) equal
to A1 to the left of Point A and label -1. From Point A ,draw
an arc (blue) toward Point B equal
to A5 (5 units). From Point 3, draw an arc (blue
dashed) toward Point C equal to 3-1 (4 units). Now, draw
lines from Point A and from Point 3 to the intersection of arcs
B & C or Point D.
- Construct a regular pentagon given the length of one side
-

Given Line AB, bisect Line AB by drawing two arcs (red)
at any radius at Points A & B that intersect at Points C & D. Next
draw a vertical line (red) from Point A to E equal in length to an arc
(red)
at Point A at a radius equal to the bisection of Line AB. From
Point B, draw a line (red dashed) through Point E and intersecting an arc (red) at Point
F equal to an arc (red) from Point E to Pont A. Now draw an arc (blue) using Points
A & B and equal to the distance from Point A to Point F.
Point G, is the center of a circle (blue) that contains the pentagon. To finish the pentagon,
draw arcs (green)
equal to the length of line AB that intersect the circle (blue) at Points
H & I. Point J is found by drawing two additional arcs (green) at Points
H & I. Connect Points BH, HJ, JI & IA inclose the pentagon
(violet).
- Inscribe a regular pentagon within a given circle -

Given Center Lines AB & CD, draw a circle of any radius and
bisect the radial center line from the center of the circle to
the edge of the circle to find the the mid-point I
using TWO equal (red) Arcs EF& HG and a (red) perpendicular line from EH to FG. Next draw an Arc (blue) from Point J where the vertical center line CD intersects
the circle to Point K on center line AB with a radius from Point
I to
Point J.
Next draw an Arc (green) from Point K on the horizontal center line AB to the circle
Point L
with a radius from Point J to Point K. This radius can be marked on the opposite
side of the circle Point P and then copied at Points M
&
N. The distance between Points M & N should be the
same as the distances between Points J
&
L, L &
M, J &
P, P &
N.
- Construct a regular hexagon within a given circle -

Given two Center Lines and a Circle of any diameter, draw TWO
Arcs (red) at Points A & D that
intersect the Circle at Points C
& B and E
& F. Now draw straight lines
(blue) from A to C,
C to E,
E to D, D to F,
F to B
and B to A to complete the hexagon.
- Divide a line into a number of equal parts -

Given a Line AB of any length, begin by drawing a Line (red) from Point A at ANY angle at ANY
length. Next, using a scale or a compass mark of the desired
number of equal parts (red &
violet) (8 in this example). From
the last Point 8, draw a Line (blue)
to Point B. Now, using TWO triangles draw additional lines (green) parallel to Line 8B at each of
the remaining Points 7 thru 1. Line AB is now divided into 8
equal parts.
- Divide a space between two parallel lines into an odd or
even number of equal spaces -

Given TWO parallel lines AB & CD at ANY distance apart, place
a scale with the zero (0) mark on
Line AB and the 5 unit mark on Line
CD. Next mark points or dots at the 1,
2, 3 and 4 unit marks and
draw lines (blue) parallel to AB
& CD at each point or dot.
- Construct a circle through three points -

Given THREE random points A, B, & C, select a radius greater
than the half of the distance between Points A & B and draw
TWO equal intersecting Arcs (red).
Draw TWO additional equal Arcs (red)
between Points B & C. Next draw TWO straight lines (blue) through the intersections of the
arcs. Finally, draw a Circle (green)
with the center at the intersection of the TWO (blue)
lines and the radius equal to the distance to A, B or C. ALL
Points should be on the (green)
circle.
- Find the center of a circle -

Given a Circle of any diameter, draw TWO straight line (red) that intersect the circumference
of the circle at Points A, B & C. Next bisect line AB (red) using TWO Arcs (blue)
and a strainght line DE (green).
THEN bisect line BC (red) using
TWO Arcs (blue) and a strainght
line GF (green). The Point H of
intersection of the TWO (green)
lines is the center of the circle.
- Create an ogee curve - connects two parallel lines with a
curve that changes direction

Given two parallel lines AB and CD, draw a line (red)
connecting the end of Line Ab at point B and the end of Line
CD at point C. Next bisect Line BC (red)
using two equal arcs (red) EF and
GH. Then draw a straight line (blue)
through the intersections of the arcs to find the midpoint of
Line BC. Now, bisect each half of Line BC using Arcs KL &
IJ as well as Arcs MN & OP and draw additional Lines (blue) at the points of intersection.
Next, draw perpendicular lines (green)
at Points B & C. The points of intersection between the (Green) Lines and the 2nd & 3rd (Blue) lines are the center points for
the Arcs (violet) that begin at
Points B & c and meet at the midpoint of Line BC.
- Create arc tangent to two straight line -

- Create arc tangent to two arcs -
Entire contents Copyright ©1998. All rights reserved. [Updated: 8/16/04]