Dimensioning 2º eso

1. THE
REPRESENTATION
OF OBJECTS
DIMENSIONING

2. 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 the
workshop and built it,
or give it to other
person and order
him it.

3. 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?

4. 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.

5. 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

6. Dimensioning
 SECOND STEP
Draw the dimension line
Representation on objects
1. It is a line drawn between
two reference lines,
parallel to the dimension
we wish to indicate.
2. It must be drawn with a
fine line too.
3. It must be separated
about 8 mm from the the
dimension we wish to
indicate.
4. The reference lines stand
above about 2 mm from
the dimension line.
Dimension
line
About 8 mm
About
2 mm

7. 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

8. Dimensioning
 FOURTH STEP
Write the dimension value
Representation on objects
1. It´s the number that indicates the
real value of the measure.
2. You mustn´t write the value but
draw it.
3. It´s always centred on the
dimension line.
4. The dimension is always expresed
in mm, so there is no need to use
the mm abbreviation.
5. It´s placed above the dimension
line (looking from down to up and
from right to left)
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Dimension
value

9. Dimensioning
 And now, let´s dimension the height
Representation on objects
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 Remember all the steps
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Reference lines Dimension line
Arrowheads Dimension value

10. Some rules
 In order to properly indicate the dimensions of an
object, we should take into account some
recommendations:
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.

11. Some rules
 In order to properly indicate the dimensions of an
object, we should take into account some
recommendations:
Representation on objects
 Avoid redundant dimensions
Is necessary this
dimension? No, because it is
the same that the
right side.
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25
25

12. Some rules
 In order to properly indicate the dimensions of an
object, we should take into account some
recommendations:
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
50
1535

13. Some rules
 If it is possible, don´t use the outline of the
piece as a dimension line.
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48

14. 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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8
3

15. Some rules
 You must avoid dimension lines to be crossed.
Representation on objects
 Unless it´s
impossible.
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4010
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16. Three ways to dimensioning a
drawing
 CHAIN DIMENSIONING
The individual dimensions
are in the same line
Representation on objects
 PARALLEL DIMENSIONING
The individual dimensions
are originated from the
same line point
 COMBINED
DIMENSIONING
It’s a combination of
chain a parallel
dimensioning

17. Some rules
 When dimensioning circumferences, the
reference lines are itself.
Representation on objects
 If the dimension value
does not fit in it, we will
draw it and the
arrowheads out.
 And we will dimension
concentrical
circunferemces in this way

18. Some rules
 And when dimensioning arcs measuring less
than 180º), we must dimension the radius.
Representation on objects
 If the dimension value or
the arrowhead do not fit
in it, we will draw it in this
way.
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

19. You must remember
 Dimension provide two types of information:
 The location of a feature
 The size of a feature
Representation on objects
Location
Size

20. Reviewing
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There are two redundant
dimensions
There is a
dimension left

21. 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

22. 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)

23. Reviewing
Representation on objects
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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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24. Examples
Representation on objects

25. Examples
Representation on objects

26. 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.