Download - Dimensioning
What is dimensioning? When we design an object, we make a sketch
or a plan.
If we are going to build it, we´ll need how it is
and, further, its dimensions.
Representation on objects
With this information, we can go to theworkshop and built it, or give it to otherperson and orderhim it.
Representation on objects
Each of the
individual measures
is called dimension.
The process of establishing
correspondences between
the dimensions of our
drawing and those of real-
world objects is called
dimensioning.
What is dimensioning?
Dimensioning
Let´s dimension the width of this rectangle to
learn how to do it.
Representation on objects
As it is a
standardized
process, you must
follow some steps.
Dimensioning is a standardized process we
must always apply when drawing.
Dimensioning FIRST STEP
Draw the reference lines
Representation on objects
1. They are two short lines
that extend outwards
perpendicularly from the
section whose dimension
we wish to indicate.
2. They must be drawn with
fine lines.
Reference
lines
Dimensioning SECOND STEP
Draw the dimension line
Representation on objects
1. It is a line drawn betweentwo reference lines, parallel to the dimensionwe wish to indicate.
2. It must be drawn with a fine line too.
3. It must be separatedabout 8 mm from the thedimension we wish toindicate.
4. The reference lines stand above about 2 mm fromthe dimension line.
Dimension
line
About 8 mm
About
2 mm
Dimensioning THIRD STEP
Draw the arrowheads
Representation on objects
1. They are two arrows
drawn at the each end
of the dimension line.
2. The arrow´s tip is an
angle of 20º
3. They must be filled
Arrowhead
Dimensioning FOURTH STEP
Write the dimension value
Representation on objects
1. It´s the number that indicates thereal value of the measure.
2. You mustn´t write the value butdraw it.
3. It´s always centred on thedimension line.
4. The dimension is always expresedin mm, so there is no need to use the mm abbreviation.
5. It´s placed above the dimensionline (looking from down to up and from right to left)
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Dimension
value
Dimensioning And now, let´s dimension the height
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Remember all the steps
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Reference lines Dimension line
Arrowheads Dimension value
Some rules In order to properly indicate the dimensions of an
object, we should take into account somerecommendations:
Representation on objects
Indicate all dimensions. If any
dimensions are missing, it will
be impossible to construct the
item for lack of information.
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Could you draw a
rectangle like this? No, you need to
know its height.
Some rules In order to properly indicate the dimensions of an
object, we should take into account somerecommendations:
Representation on objects
Avoid redundant dimensions
Is necessary this
dimension? No, because it is
the same that the
right side.
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Some rules In order to properly indicate the dimensions of an
object, we should take into account somerecommendations:
Representation on objects
Avoid those dimensions
easily deducible from
dimensions already
indicated.Is necessary this
dimension?
No, because you
can calculate it by
substracting 50-15
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15
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Some rules If it is possible, don´t use the outline of the
piece as a dimension line.
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Some rules If the arrowheads don´t fit in the dimension,
you´ll draw them outside.
Representation on objects
And if there is no place for the dimension value, you´ll draw it outside too.
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Some rules You must avoid dimension lines to be crossed.
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Unless it´s
impossible.
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Three ways to dimensioning a
drawing
CHAIN DIMENSIONING
The individual dimensions
are in the same line
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PARALLEL DIMENSIONING
The individual dimensions
are originated from the
same line point
COMBINED DIMENSIONING It’s a combination of chain a parallel dimensioning
Some rules When dimensioning circumferences, the
reference lines are itself.
Representation on objects
If the dimension valuedoes not fit in it, we willdraw it and thearrowheads out.
And we will dimension
concentrical
circunferemces in this way
Some rules And when dimensioning arcs measuring less
than 180º), we must dimension the radius.
Representation on objects
If the dimension value orthe arrowhead do not fitin it, we will draw it in thisway.
The dimension
value is preceded
by the letter R
It must be
indicated the
center of the circle
There is no arrowhead
in this edge of the
dimension line
You must remember
Dimension provide two types of information:
The location of a feature
The size of a feature
Representation on objects
Location
Size
Reviewing
Representation on objects
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There are two redundant
dimensions
There is a
dimension left
Reviewing
Representation on objects
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The dimension line is too
near from the outline of
the piece
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The dimension line is too
far from the outline of the
piece
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The arrowheads are too
long
The arrowheads are too
thick
Reviewing
Representation on objects
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The dimension value must
be placed above the
dimension line (looking
from down to up and
from right to left)
Reviewing
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The reference lines stand
above less than 2 mm
The reference lines stand
above more than 2 mm
The dimension value is on
(not above) the
dimension line
The dimension value is
not centered
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Examples
Representation on objects
The purpose of dimensioning is to provide a clear and complete description of an object.
A complete set of dimensions will permit only one interpretation needed to construct the object, although the set of dimensions is not an only one.
So, dimensioning should follow these guidelines:
Accuracy: correct values must be given.
Clearness: dimensions must be placed in appropriate positions.
Completeness: nothing must be left out, and nothing duplicated.
Readability: the appropriate line quality must be used for legibility.