Complete presentation about technical drawing applied to Technology in 3º of ESO

1. Graphic representation of
technological projects

3.  Expression of ideas, feelings and emotions
through drawing.
 It’s used to express ideas… from very simple to
really complex.
 Drawing is a universal language.
 Written characters are drawings.

4.  Artistic drawing:
- No rules. Freedom.
- Used to express emotions or to create beauty.
- Broad variety of tools.
- It can be messy and caotic.
 Technical drawing:
- International rules.
- Used to transmit ideas and create projects.
- Made with tools that achieve accuracy.
- It must be clean and ordered.
Accuracy: Precision.
You must present
cleanly and
orderly FOR REAL.
A percentage of
your drawing’s
mark will always
depend on their
cleanliness and
presentation.

5. Do the following drawings transmit ideas or
feelings?
Do you think they are artistic or technical drawings?
Are they graphic representations of things?

10.  Looking for solutions to a problem.
 Organizing ideas.
 Designing objects in detail (parts, dimensions,
assembly…)
 Showing ideas to other people and debating
about them.
 Giving instructions to assemble a product.
 Adding aesthetic value to a design.
To assemble: To mount, put together.
Aesthetic: Tasteful, beautiful.
LOOK AT the spelling of this word:
D-E-S-I-G-N

12. DIN A4
210 x 297 mm
21 x 29,7 cm
DIN A3
297 x 420 mm
29,7 x 42 cm
DIN A2
Can you guess
its size?
DIN A1
Can you guess
its size?
DIN A0
Can you guess
its size?

13.  They are used directly on paper to draw.
 PENCILS Hardness.
H = Hard (the higher its number, the harder)
HB= Medium
B = Bland (the higher its number, the softer)
 TECHNICAL PENS  Thickness.
 FELT-TIP PENS  Colour.
Using the right pencil for every
situation will be crucial for your
marks.

14.  They help us to draw accurately.
T-SQUARE SQUARE

15. PROTRACTOR
RULER
COMPASS
LOOK AT the spelling of this word:
P-R-O-T-R-A-C-T-O-R

16. First place the long side
of the T-square in contact
with your reference line
To draw parallel lines,
slide the T-square
To draw
perpendicular lines,
turn the T-square
around without
moving the Square
Slide the T-square
and draw on its
long side.
You must control this
technique FOR REAL. A
percentage of your
drawing’s mark will always
depend on the accuracy of
your parallel and
perpendicular lines.
Parallel lines: Never meeting or
spreading away.
Perpendicular lines: Crossing at a
straight angle (90º).

18.  Rough lines, rapidly executed
 Normally it consist of a multitude of overlapping
lines (we use no rubber)
 Not finished
 Creating  Used to think, discuss about possible
solutions, define measurements, solve details
about certain parts, designing the assembly
process…
 Observing  Used to take notes from real objects
like measurements, materials, shape…
Freehand: drawn using
no auxiliary tools.
Rough: Unfinished.
Overlapping: Lying ones
over others.

19. They can be more or less detailed
depending on the stage of the
creative process.
LOOK AT the right
preposition:
To depend ON
something
Stage: Phase, step.

23.  GRAPHIC  Only based on lines,
symbols and numbers.
 UNIVERSAL  Understandable by any technician in
the World.
 PRECISE  Drawn with care, cleanliness and
accuracy.
 COMPLETE  Including every detail necessary to
build the object (measurements, materials, parts,
assembly…)
 APPROPRIATE  Every drawing requires a different
scale, level of detail, medium… depending on its
final user.
LOOK AT the right
preposition:
To be based ON
something

25. In the context of technical drawing, Standardisation
is the set of rules that regulate all the elements
that form part of graphic representation.
Standardisation allows for a drawing to be
understood internationally.
Some set of rules:
 AENOR in Spain
 DIN in Germany
 UNE in Europe
 ISO international
 ANSI, ASA in the USA
Standardisation regulates:
 Paper formats
 Line types
 Annotation
 Scales
 Labelling
 Abbreviations (…)

26. Labelling is the set of letters, numbers and symbols that
go with a drawing to complement it.
We will use the following rules:
 Labelling must be done freehand.
 The letter’s height must be appropriate for the
drawing. Some standard heights are (mm):
2’5 3’5 5 7 10 14 20
 Use a 2H very sharp pencil.
 Lines must be dark and well traced.
 Your letter must be vertical and technical.
 Auxiliary soft parallel lines must be used.
To trace: To draw.
A set of: A group of.
From now on, all
labelling you need
to include in your
drawings must be
made respecting
these rules.

27. On a page of your drawing pad, trace 3 pairs of
auxiliary lines at a 7 mm distance. Spacing: 3’5
mm.
Write your name and surname in capital and small
letters in the first two pairs of lines.
Write your birth date in the third pair of lines.
Spacing: The free
space between two
written lines.
Use this vertical
standardized
labelling style
(DIN17).

28. There are two main line types:
 Lines that define the drawing. Types:
a) Continuous thick lines (2B)  Edges and cuts.
b)Dashed thin lines (2H)  Hidden edges.
c) Dashed thin lines with dots (2H)  Axis of
symmetry.
 Auxiliary lines.
Continuous thin
lines (2H).

29. On the page where you
practice your labelling,
draw a sketch of the three
flat views of this object.
Try to keep the proportions
although you don’t know
its measurements.
Now, draw them with your
set squares using the right
types of lines.

30. Annotation consists of expressing the real measurements
of an object on a plan.
Annotation makes the plan easier to read and interpret. It
allows us to see the measurements of an object at a
glance.
Annotations must be clear, clean
and precise:
a) Drawn more lightly than the
lines of the drawing.
b) Parallel lines must be REALLY
PARALLEL.
c) The size of the numbers must
be not too big nor too small.
Plan: Technical drawing
that represents a view of
an object or building.
LOOK AT the right
spelling:
A-N-N-OTATION

31. a) Extension lines Thin, continuous (2H)  They
indicate the portion of the drawing we are
measuring.
b) Annotation lines Thin, continuous (2H) 
Parallel to the edge (at the right distance) and
measuring the same.
c) Arrow heads  Thin (2H)  On both annotation
line endings, they indicate the dimension labelled.
d) Annotation  Thin and correctly labelled (vertical
standard writing) (2H)  Number that indicates
the real measurement of the portion annotated.

32. Arrow head
Annotation line
Annotation
Extension
line
Different arrow head styles
Pay attention to all these rules and learn by
practising. A drawing needs to abide by these
rules to be good.

33. 1- Annotations must never be written on the edge but on
top of the annotation line.
2- Annotation lines must never cross, touch or overlap an
edge of the object. Extension lines must be used. Leave
a reasonable distance (0,8 cm minimum) between
edge and annotation line.

34. 3- Extension lines extend 2-3
mm from the annotation
line. They must touch the
edge they are marking.
4- Annotations must be
placed above the line and
centered on it. On vertical
edges, think about a
clockwise turn.
5- The units must never be
indicated on the annotation.
We just write the
measurement (normally in
mm) and express the units
on the plan.
DIMENSIONS IN mm

35. 6- You must indicate all necessary measurements for
building the object.
7- You must not repeat any measurement
unnecessarily.

36. 8- Annotation lines must never cross nor cross an edge. It’s
fine to cross two extension lines or an extension line and
an edge.
To avoid crossing, we must plan the position of the
annotation lines carefully.

37. 9- We must arrange annotations in an orderly way.
Standard
annotation
systems

38. ANNOTATION OF ARCS AND
CIRCUMFERENCES
 We use the SYMBOLS R (radius) y Ф (diameter).
 We draw with DASHED LINES WITH DOTS two
diameters (vertical and horizontal) and the center of
the arc/circumference. The annotation line must be
DIAGONAL.
 If the annotation doesn’t fit inside, we can extend the
annotation line and write it ouside.

39. ANNOTATION OF
PERSPECTIVE DRAWINGS
Extension and annotation
lines must always be
parallel to the edges of
the object.

40. Go back to the front
view of this object
you drew in your
pad.
Measure it and write
annotations,
following all the
rules.

43.  FLAT VIEWS
The flat views (o dihedral views) of an object are 2 dimension
images perceived by an observer placed on a plane parallel
to the object’s main sides.
We draw them following the European system.
 PERSPECTIVE Plane: A flat or level surface.
Drawing a perspective is
trying to show a 3
dimensional reality onto a 2
dimensional medium.
The perspectives that we’ll
use are cavalier and
isometric perspectives.
Dihedral: having or containing
two plane faces.

44. Remember:
NOUN - ADJECTIVE
Height – High
Depth - Deep
Width - Wide
Front, side and top views are
the result of projecting an
object onto an imaginary
trihedron.
That trihedron, with the 3
projections, later unfolds
and shows the views in
correlative positions.
Trihedron: Volume formed by
three planes that intersect at
three 90º angles.

45. 2nd step: Name the three
axes x, y, z on the
perspective and draw
them in 2D. Draw a
line at a 45º angle in
the bottom right
sector.
z
y
x
z
y
x
x
1st step: Colour what’s seen from every
different view point. A slope is seen
from two view points.
LOOK AT the singular and
the plural:
AXIS (singular)
AXES (plural)
You must always label all
three axes and use the 45º
line.

46. 3rd step: Draw the front
view in the xy sector.
Keep the measurements
of the perspective.
Don’t make your view
lean on (touch) the
axes.
4o step: Draw the side view
in the xz sector at the
same height as the
front.
5th step: the top view in the
xy sector using the 45º
line. It must be right
under the front view.
z
y
x
IMPORTANT: The three views must be
correlatively placed. We use auxiliary soft
lines and the 45º angle line to achieve that .
REMEMBER: Hidden edges are represented by
dashed lines. Symmetry axes by dashed lines
with dots.
z
y
x
x
Front
view
Front view Side view
Top view

47. Draw the three
views of these
objects with
your set squares
on a page of
your drawing
pad. Keep the
measurements:
a little cube is 3
cm side.

48. It’s a 3 dimensional representation of an object
formed by three axes separated by 120º angles.
The true dimensions of the object are respected (we
consider no distortion because of the depth, which
is not realistic). Distortion: Deformation.

49. We can easily trace the axes using our set squares:
You must practise this
technique until you are able
to do it without help.

50. On one of your pad’s pages, draw the three axes at
120º and then draw this cube of 6 cm side.
First, draw everything softly
with your 2H pencil.
Then, outline all visible edges
with your 2B pencil (don’t
erase anything).

51. On one of your
pad’s pages,
draw these
objects.
Remember that they
are based on a
small 3cm side
cube.
First, draw everything
softly with your 2H
pencil.
Then, outline all visible
edges with your 2B
pencil (don’t erase
anything).
Your teacher will teach you the process you must
always follow when you want to draw an isometric
perspective. Learn and use this method, ALWAYS.

52. On a pad’s page, draw the three axes at 120º 7 times,
using your set squares.
Then draw a sketch of all these pieces of furniture.
First, draw everything softly with
your 2H pencil.
Then, outline all visible edges with
your 2B pencil (don’t erase anything).
Remember your
teacher’s method.

53. Draw this chair on a page of your drawing pad, using
your set squares. Imagine the dimensions are in
mm.
Don’t annotate!
First, draw everything softly with
your 2H pencil.
Then, outline all visible edges
with your 2B pencil (don’t erase
anything).
Remember your
teacher’s method.

54. Draw these object on a pad’s page in the isometric
perspective, respecting the dimensions and using
your set squares. Don’t annotate.
Remember your
teacher’s method.

55. Draw these object on a pad’s page in the isometric
perspective, respecting the dimensions and using
your set squares. Don’t annotate.
Then, draw the three flat views of the object at the
same scale.

57. The scale is the relation between the measurements in
a drawing and the real measurements of a physical
object.
S=1  Natural scale (1:1)
Objects are represented as they are, so there’s no confusion.
e>1  Enlargement scale
It’s used to draw small objects bigger than they are, so we can
represent details (2:1, 10:1…).
To guess the real measurements, we’ll divide the size in the drawing by the scale.
e<1  Reduction scale
It’s used to represent big objects smaller than they are, so
they can fit the paper (1:75, 1:100, 1:1000, 1:10.000…).
To guess the real measurements, we’ll multiply the size in the drawing by the scale.
Measurements in the plane
Scale =
Measurements in reality

58. What scale type would you use to represent…?
- A truck.
- A mobile phone.
- The roads net of a country.
- A pin.
- A screw.
- A house.
- A computer’s motherboard.
- The human body’s muscles.
- A dragonfly.
- A cell.

59. An area is represented on a 1:5.000 map. How many
kilometers will separate two towns in the real
territory, if they are separated by 20 cm in the map?
We solve this using a rule of three:
DRAWING REALITY
1 cm in the map____________ 5.000 real cm
20 cm in the map___________ x real cm
x = 20 · 5.000 / 1= 100.000 cm = 1 km
Understand and
use this method
for all these
problems.
PAY
ATTENTION TO
UNITS!!!!

60. What scale shall we use to represent a football pitch
measuring 75 x 100 m so that it fits a Din-A3 paper
(42 x 29,7 cm)?
We solve this by a rule of three, thinking of the long
side of the paper and leaving a bit of free space:
DRAWING REALITY
1 cm in the plane____________ x real cm
38 cm in the plane___________ 10.000 real cm
x = 1 · 10.000 / 38= 263 cm
Escala: 1:300

61. When we want to choose the scale to represent a
certain object on a plane, we must take into
account that there is a series of standardized
scales:
Reduction scales
Enlargement
scales
Manufacturing and
installations
Arquitecture, building and
civil works
Topography and
Geography
Urbanism