TECHNICAL

DRAWINGTECHNICAL DRAWING & BASIC GEOMETRIC CONSTRUCTIONS

JULIA MENA GARCÍA

CIRCLES

CIRCLES

OPEN PAGE 88 ON YOUR BOOK

-LOOK THESE WATER LILY PLANTS, AND THOSE ORANGES CUT IN HALF.

-NAME AS MANY CIRCULAR THINGS YOU CAN THINK OF THAT ARE FOUND IN REAL LIFE.

LET’S SEE THE DIFFERENCES BETWEEN...

A CIRCLE AND AN ELLIPSE

A circle has only one axis, while an ellipse has two.

LET’S SEE THE DIFFERENCES BETWEEN...

A CIRCLE AND AN SPHERE

A circle is two dimensional while a sphere is three dimensional

CIRCLE SPHERECIRCUMFERENCE

USING THE COMPASS

A compass is used to make curved shapes or circles. It is also used to create line segments of equal lenght.

It is an easy to use and precise drawing tool. In technical drawing, compasses are used for inscribing perfect circles or arcs.

The compass can be named as well as a pair of compasses.

THE CIRCUMFERENCE

A circumference is the length of the closed curved line of the circle.

A circle has a centre point and every point on the closed curved line is the same distance from the centre point.

EXERCISENow do the exercise 9 on page 87. Draw a circumference knowing three points and no centre.

OPEN PAGE 87 ON YOUR BOOK

LET’S DO THE EXERCISE

Join points A and B and draw the line segment bisector.

90º

Then do the same thing with points B and C.

Note that the point where both perpendicular bisectors cross is the centre of the circumference.

-Finally, draw a circumference using that point as the centre and any of the other points.

RADIUS

-Finally, draw a circumference using that point as the centre and any of the other points.

RADIUS

-Concentric circumferences have the same axis.

-A tangent interior circumference touches the interior circumference of another circle.

-An external circunference doesn’t touch the other circumference.

-An intersecting circumference intersects another circumference in at least two points.

EXTERNAL CIRCUMFERENCE INTERNAL CIRCUMFERENCE

TANGENT EXTERIOR CIRCUMFERENCE

TANGENT INTERIOR CIRCUMFERENCE

CONCENTRIC CIRCUMFERENCES

INTERSECTING CIRCUMFERENCE

OPEN PAGE 87 ON YOUR BOOK

LET’S DO THE EXERCISE

OPEN PAGE 87 ON YOUR BOOK

EXAMPLE

OPEN PAGE 81 ON YOUR BOOK

WE WILL LOOK AT HOW TO CARRY OUT SOME COMMON GEOMETRIC CONSTRUCT IONS USING A COMPASS AND A RULER.

CREATE A FREE COMPOSIT ION MADE UP OF CIRCLES USING A COMPASS AND THEN COLOUT THEM WITH PENCILS OR FELT-T IP PENS.

IF YOU HAVE COMPASS ADAPTOR & EXTENSION, YOU CAN USE THEM TO VARY THE SIZE AND DRAW THE SHAPES WITH THE COLOURS.

EXAMPLE