Transcript INTRODUCTION TO TECHNICAL DRAWING.

WEEKS
TOPICS
1. Introduction to technical drawing, lines,
lettering, dimensioning and safety measures.
2. Uses and cares of equipment.
3. Drawing board practice and types of drawing.
4. Division of lines into given number of parts or
proportion.
5. Angles.
6. Triangles.
7. Quadrilateral figures.
8. Polygons.
9. Circles.
10. Revision / Examination.
MEANING OF TECHNICAL DRAWING
Technical drawing is a language used in the
workshop to convey an idea and instruction.
It involves drafting or draughting. That is,
the act and discipline of composing plans
that visually communicate how something
functions.
The following are safety measures in
technical drawing;
1. Always pay attention while drawing.
2. The right drawing tools must be used for
the right job.
3. Always observe neatness while drawing.
4. Always keep your pencil well sharpened.
5. All drawing instruments must be properly
kept.
A line has position, length but virtually no
thickness.
A line may be straight or curved.
A straight line is regarded as the shortest distance
between two points. While a curved line is the
longest distance between two points as shown
below.
A
A
A straight line
A curved line
B
B
The following are the different types of lines.
1) Thin continuous line : It is used for construction,
projection, hatching and dimension lines.
2) Thick continuous line: This is used for visible outlines
and edges.
3) Thin short dashes : lt is used for showing hidden
outlines and edges.
4) Thin long chain : This is used for centre lines and
extreme positions of moveable parts.
5) Thick long chain : It is used for cutting planes.
6) Thin wavy lines: This is used for limits of partial
views or sections when the line is not an axle.
7) Arrow head lines: It is used for indicating
directions and at the end of dimension lines:
8) Thick wavy lines: it is used for short break lines
and irregular boundary lines.
9) Thin ruled with short zig-zags : used for long
break lines.
It is the act of indicating the size of an object when
drawing, using an arrow head lines and thin
continuous lines as shown below.
TYPES OF DIMENSIONING.
1. Chain dimensioning is advantageous because
the size of each feature is easy to read and is
economical in space. The disadvantage is that
error measurement can be cumulative that leads
to large error on the overall size of the object.
2. Datum dimensioning: It enables us to measure
independently from one edge and consequently
errors are not cumulative.
This is the act or way of writing clearly a word or
statement. Lettering technique is used for designing sign
post or board.
Lettering can be done freehand or by mechanical means
whereby stencil is used to print out the words.
STYLES OF LETTERING
The following are the styles of lettering
1. Gothic, 2. ltalic, 3. Celtic
Lettering is either straight or slanting as shown below.
CHRISLAND SECONDARY SCHOOLS, LAGOS.
CHRISLAND SECONDARY SCHOOLS, LAGOS
.
As shown above, lettering must be done in between
two lines to maintain the same height and size.
 CLASS
WORK
 1.What is technical drawing?
 2. State 3 safety measures observed
in technical drawing .
 3. What is a line in technical
drawing?
 4. State the uses of 5 types of line
used in technical drawing.
 5. Design a sign post for chrisland
schools.