dimensioning

THE

REPRESENTATION

OF OBJECTS

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.


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.


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


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


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


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


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)

40

Dimension

value

Dimensioning And now, let´s dimension the height


40

Remember all the steps

40 40

40 40

25

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:


Indicate all dimensions. If any

dimensions are missing, it will

be impossible to construct the

item for lack of information.

40

Could you draw a

rectangle like this? No, you need to

know its height.




Avoid redundant dimensions

Is necessary this

dimension? No, because it is

the same that the

right side.

40

25

25




Avoid those dimensions

easily deducible from

dimensions already

indicated.Is necessary this

dimension?

No, because you

can calculate it by

substracting 50-15

50

15

35

Some rules If it is possible, don´t use the outline of the

piece as a dimension line.


48

48

Some rules If the arrowheads don´t fit in the dimension,

you´ll draw them outside.


And if there is no place for the dimension value, you´ll draw it outside too.

8

8

3

Some rules You must avoid dimension lines to be crossed.


Unless it´s

impossible.

10

4010

40

42

40

Three ways to dimensioning a

drawing

CHAIN DIMENSIONING

The individual dimensions

are in the same line


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.


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.


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


Location

Size

Reviewing


40

25

40

25

40

25

40

25

40

There are two redundant

dimensions

There is a

dimension left

Reviewing


40

The dimension line is too

near from the outline of

the piece

40

40

The dimension line is too

far from the outline of the

piece

40 40 40

The arrowheads are too

long

The arrowheads are too

thick

Reviewing


40

25

40

25

40

25

40

25

40

25

40

25

The dimension value must

be placed above the

dimension line (looking

from down to up and

from right to left)

Reviewing


40

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

4040

40 40 40

Examples


Examples


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.

dimensioning

Education

dimension linerepresentation

dimension lineabout

dimension valuerepresentation

height representation

reference linesrepresentation

fine lines

short lines

standardized process