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30
SECTION 1
3
Brainstorming
Look at the pictures and note the scale used when drawing them and their real
dimensions, then solve the problem below.
Problem
The scale drawing of this tree is
1:500. If the height of the tree on paper is 20
inches, what is the height of the tree in real life?
4
Read the passage in detail then answer the following questions.
a
What are the main parts of a drawing?
b
What information will you find in the title block?
c
What does ‘tolerance’ indicate?
d
What is a scale?
Real horse 1500 mm high.
Drawn horse 150 mm high.
Height = 20 inches
Conventions – sCale – toleranCe in working drawings
B
efore computers became widely available, every drawing was produced by hand. Companies employed teams of
skilled draughtsmen to turn their designers’ ideas into working drawings.
The drawings were produced using black
ink
and
drawing boards
; it was useful to have set squares, including a
T-square
, pencils,
erasers
, and a
ruler
.
It was, and is very important that any designer, engineer, or machine operator can look at a working drawing and
immediately understand it, it must be very clear and use the same terms. This is why there are a lot of rules and
conventions that specify how a drawing must be presented.
It is a general
convention
that the drawings should have a
border
and a title block.
The border normally contains zone references, so that people discussing the drawing can easily be directed to the
features that they are talking about.
The title block should contain: the title, the number, the date, the name and signature of the person who made
the drawing, the scale and the projection used, and any other information needed to make the part, including the
materials to be used.
The part must be
drawn to scale
, which means that its measurements must each be in proportion to the
size
of the finished part. It should be stated as a ratio, for example 1:1 (full size), 1:2, 1:5 (smaller than full size), 2:1, 5:1
(larger than full size).
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Progetto FOR MECHANICALS_unit_1.indd 30
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