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34
SECTION 1
12
Read the passage and answer the following questions.
a
What has to be taken at 20°C?
b
List the main measuring tools.
c
List the most common marking out tools?
d
Explain the difference between the metric system and the Imperial system.
13
There are many types of gauges, look at the pictures below and match them with the terms in the box.
Measuring equipment
L
ength is the most important measurement quantity in
mechanical engineering. The standard international
unit of length in Great Britain, Europe and most of the
world, is measured using the metric system that is
divided into 1,000 equal parts called millimetres.
But many American companies use the Imperial system
(inch or fractions of an inch) and so engineers and
craftsmen have to be familiar with both systems.
All measurements must be taken at a standard
temperature of
20° C
to avoid errors caused by changes
(expansion, contraction etc.) in the material due to
temperature change and difference.
A wide range of tools for measuring and marking out
are available. The choice of the measuring tool is made
depending on the accuracy required, the dimensions
(linear and angular), on access to the feature to be
measured, on the shape and size of the feature etc.
The most common measuring tools are:
rulers
,
tape
measures
,
callipers
,
squares
,
protractors
,
calliper gauges
,
gauges
,
micrometers
and
Vernier callipers
.
Some commonly used marking out tools are:
scribers
,
pens
,
pencils
,
dot
and
centre
punches
1
, and
dividers
.
1
punch
: the centre punch is made from mild steel with the
point hardened and tempered so that it withstands impact
with the material it is marking. It is normally used to mark the
centre of a hole to be drilled either by hand or on the drilling
machine. The dot punch is a lighter and thinner version of the
centre punch and is used basically for the same job. However,
it is more accurate as the dot produced is smaller
TEXT 5
calliper gauge
calibro fisso
calliper
calibro
divider
compasso a punta fissa
gauge
calibro
micrometer
micrometro
protractor
goniometro
punch
punzone, punteruolo
scriber
punta del compasso
tape measure
metro a nastro
Vernier calliper
compasso verniero
TECHNICAL ENGLISH
Tape measure.
depth gauge drill gauge radius gauge screw pitch gauge wire gauge
Progetto FOR MECHANICALS_unit_1.indd 34
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