dimensioning standard
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Dimensioning
Standards
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Rules and Practices
Accurate dimensioning is one of the most
demanding undertakings when designing parts.
Use the checklist to insure you have followedthe basic dimensioning rules.
Keep in mind there may be a case where theneed to break a standard could occur to give
clarity to the part and manufacturer.
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Standards
In order for the drawings to be dimensioned
so that all people can understand them, we
need to follow standards that every company
in the world must follow. Standards are
created by these organizations
!A"SI !#I$
!IS% !&%&!&I" !'("
!)IS
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Standards Institutions
A"SI ! American "ational Standards Institute
! *his institute creates the engineering
standards for "orth America.
IS% ! International %rganization for
Standardization ! *his is a world wide
organization that creates engineering
standards with appro+imately --
participating countries.
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Standards Institutions
&I" ! &eutsches Institut fr "ormung ! *he
/erman Standards Institute created many
standards used world wide such as the
standards for camera film.
)IS ! )apanese Industrial Standard ! 'reated
after 00II for )apanese standards.
'(" ! (uropean Standards %rganization
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Standards Institutions
*he 1nited States military has two organizations
that develop standards.
&%& ! &epartment %f &efense #I$ ! #ilitary Standard
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$inear dimensions are comprised of
four components
ExtensionLines
Dimension Text Dimension Lines
Arrow 2eads
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(+tension $ines
(+tended from the
view to indicate the
edges referencedand hold the
dimension line
345 gap from the
view so they are not
confused with the
visible lines
'ontinue 365 pastthe dimension line
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&imension $ines
2orizontal
Aligned to a slanted
surfaced
7ertical
0hen stacked, they
are -mm 8.95: fromthe view and
4mm8.;
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Arrowheads8&imension $ine *erminator:
Arrowheads are typical dimension line terminators. *here are other
acceptable dimension line terminators.
Arrowheads point directly
to the ob=ect that is being
dimensioned or the
e+tension lines at the endof the dimension.
Arrowheads are made
three times as long as
they are wide.
&ot
%bli>ue or architectural ticks
used in architectural drawings &atum
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&imension *e+t
&imension te+t is
placed in themiddle of the line
both horizontally
and vertically.
If the dimension te+t will not fit between thee+tension lines, it may be placed outside
them.
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&imensioning #ethods
&imensions are represented on a drawing using
one of two systems, unidirectional or aligned.
*he unidirectionalmethod means all dimensions
are read in the same direction. *he alignedmethod means the dimensions are
read in alignment with the dimension lines or
side of the part, some read horizontally and
others read vertically.
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&imension *e+t1nidirectional vs. Aligned
1nidirectional
dimensions are placed
so they can be read from
the bottom of thedrawing sheet. *his
method is commonly
used in mechanical
drafting.
Aligneddimensions are placed
so the horizontal dimensions can
be read from the bottom of the
drawing sheet and the vertical
dimensions can be read from the
right side of the drawing sheet.
*his method is commonly used in
architectural and structural
drafting.
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*ypes of &imensions
*here are two classifications of dimensions sizeand location.
Size dimensions are placed in directrelationship to a feature to identify the specificsize.
Location dimensions are used to identify the
relationship of a feature to another feature withinan ob=ect.
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&imensioning 'hecklist (ach dimension should be written clearly
with only one way to be interpreted.
A feature should be dimensioned only once.
&imension and e+tension lines should notcross.
(ach feature should be dimensioned.
&imension features or surfaces should bedone to a logical reference point.
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&imension 'hecklist
&imension circles should havediameters and arcs with a radius.
A center line should be e+tended andused as an e+tension line.
&imension features on a view should
clearly show its true shape. (nough space should be provided to
avoid crowding and misinterpretation.
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&imension 'hecklist
(+tension lines and ob=ect lines
should not overlap.
&imensions should be placed outsidethe part.
'enter lines or marks should be used
on all circles and holes.
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$inear &imensioning
&imensioning from feature to featureis known as Chain Dimensioning.. Itis commonly used and easy to layout. It does have possibleconse>uences in the manufacturingof a part. *olerances can
accumulate, making the end productlarger or smaller than e+pected.
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'hain &imensioning
*his is a general note. Itindicates that all two
place decimal
dimensions have a
tolerance of plus or
minus .- inch unless
otherwise specified.
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'hain &imensioning(ach of these steps
can range between .
9?-5
and .
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'hain &imensioning
*he chain dimensioning
layout can have an effect
on the final length of the
part ranging from .9@to .
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'hain &imensioning
Placing an overall dimension
will limit the chain effect of the
tolerance build up.
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$inear &imensioning
*he accuracy of the final product is
determined by the dimensions on the
drawing. If all the dimensions originate
from a common corner of the part, theob=ect will be more accurate. *his is
referred to asDatumDimensioning.
&atums insure the tolerance or errors inmanufacturing do not accumulate.
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&atum &imensioning
The dimensionsoriginate from a
common edge (DATUM)
of the part.
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&atum &imensioningThe dimensionsoriginate from acommon edge
(DATUM)of the part.
*his is a general note. It
indicates that all two place
decimal dimensions have a
tolerance of plus or minus .
- inch unless otherwise
specified.
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&atum &imensioning
*his step can be .9?-
to .
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&imensioning Symbols
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&imensioning Angles
Angled surface may be dimensioned
using coordinate methodto specify
the two location distances of theangle.
Angled surfaces may also be
dimensioned using the angularmethodby specifying one location
distance and the angle.
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&imensioning Angles
'oordinate #ethod Angular #ethod
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&imensioning Arcs and
'ircles
Arcs and circles are dimensioned in viewsthat show the arc or circle.
Arcs are dimensioned with a leader toidentify the radiusB in some cases, acenter mark is included.
'ircles should have a center mark and aredimensioned with a leader to identify thediameter.
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Day two .
Drafting 2
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&imensioning 'urved Ceatures
and Arcs
1se a capital DR5 for
dimensioning arcs.
$arge Arcs use center
marks.
Small arcs do not need
center marks. Arrow can
be outside.
*he arrow can be inside
for small arcs.
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&iametersA full circular ob=ect should be dimensioned
using its diameter. 2oles should use hole
notes.
*his specification
calls for a hole with
a .< diameterand .-- deep.
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&iameters'ylindrical parts may show their diameters in this
manner. &imensioning on the right side view
could be too crowded.
"ote that the diameter symbol is used so it
is not confused with a linear dimension.
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'hords
'hords may be dimensioned in one of
the following ways.
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&imensioning 'urved Ceatures
&atum
Points are placed along the contour
and are dimensioned from the datum.
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Reference &imensions&esignates more than one of the same feature.
In this case, it is identifying there are
two identical holes.
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'hamfers(+ternal chamfer for 9< degree
chamfers only.
*here are two options.
(+ternal chamfer for angles other than
9< degrees.
Internal chamfers.
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Cillets and Rounds
Rounds
Cillets
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Cillets and Rounds
1se a capital DR5 for
dimensioning the arc.
$arge arcs use center marks.
Small arcs do not need
center marks. Arrow can
be outside the arc.
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'onical *apers
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Slot &imensioning
*he two methods
shown on the left
are the acceptable
methods fordimensioning slotted
holes.
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&imensioning Radial
Patterns Angles and radius valuesare used to locate the centersof radial patterned features,
such as the holes on
this plate.
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Eeyway and Eeyseat
Eeyway Eeyseat
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Shaft
EeywaysEeyway &imensions
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2ole &imensioning
2oles are specified
with numbers and symbols.
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Reading a 2ole "ote
*he 2ole &iameter is .;
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Reading a 2ole "ote
*he 2ole &iameter will be
.65 drilled .< deep.
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Reading a 2ole "ote
*he 2ole &iameter will be .65
through the whole block.
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Reading *hread "otes
*hreads are dimensioned with
the use of local notes. 0e will
discuss two methods the IS%
and the 1nified "ational *hread
method.
R di 1 ifi d " i l
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Reading a 1nified "ational
*hread "ote
#a=or &iameter
*hreads per InchIdentifies coarse or fine
thread. In this case, ' for coarse.
C is for fine.
R di IS% *h d "
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Reading a IS% *hread "otes
# for #etric
"ominal &iameter
In #illimeters
Pitch of the threads.
*his number can be ,9,
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&imension
/uidelines
&i i h ld "%* b d li t d
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. &imensions should "%* be duplicated, or
the same information given in two different
ways.
Incorrect
&i i h ld "%* b d li t d
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. &imensions should "%* be duplicated, or
the same information given in two different
ways.
; " di i h ld b
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;. "o unnecessary dimensions should be
used F only those needed to produce or
inspect the part.
Incorrect
; "o nnecessar dimensions sho ld be
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;. "o unnecessary dimensions should be
used F only those needed to produce or
inspect the part.
&imensions should be attached to the view
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. &imensions should be attached to the view
that best shows the contourof the feature
to be dimensioned.
Incorrect
&imensions should be attached to the view
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. &imensions should be attached to the view
that best shows the contourof the feature
to be dimensioned.
9 0henever possible avoid dimensioning to
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9. 0henever possible, avoid dimensioning to
hidden lines and features.
Incorrect
9 0henever possible avoid dimensioning to
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9. 0henever possible, avoid dimensioning to
hidden lines and features.
< Avoid dimensioning over or through the
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4. A dimension should be attached to only
one viewB for e+ample, e+tension lines
should not connect two views.
Incorrect
4 A dimension should be attached to only
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4. A dimension should be attached to only
one viewB for e+ample, e+tension lines
should not connect two views.
@ 0henever possible locate dimensions
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@. 0henever possible, locate dimensions
between ad=acent views.
Incorrect
@ 0henever possible locate dimensions
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@. 0henever possible, locate dimensions
between ad=acent views.
6 Avoid crossing e+tension lines but do not
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#ultiple
e+tension
linecrossings
may be
confused for
the outsidecorner of the
part.
6. Avoid crossing e+tension lines, but do not
break them when they do cross.
? 0henever possible avoid sending
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?. 0henever possible, avoid sending
e+tension lines through ob=ect views.
Incorrect
? 0henever possible avoid sending
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?. 0henever possible, avoid sending
e+tension lines through ob=ect views.
- In general a circle is dimensioned by its
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-. In general, a circle is dimensioned by its
diameter and an arc by its radius.
2oles are located by their centerlines
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. 2oles are located by their centerlines,
which may be e+tended and used as
e+tension lines.
; 2oles should be located and sized in the
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;. 2oles should be located and sized in the
view that shows the feature as a circle.
Incorrect
; 2oles should be located and sized in the
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;. 2oles should be located and sized in the
view that shows the feature as a circle.
&o not cross a dimension line with an
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. &o not cross a dimension line with an
e+tension line, and avoid crossing
dimensions with leader lines.
&o not cross a dimension line with an
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. &o not cross a dimension line with an
e+tension line, and avoid crossing
dimensions with leader lines.
9. $eader lines point toward the center of the
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9. $eader lines point toward the center of the
feature, and should not occur horizontally
or vertically.
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4. 'oncentric circles are dimensioned in the
longitudinal view, whenever practical.
Incorrect
4. 'oncentric circles are dimensioned in the
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4. 'oncentric circles are dimensioned in the
longitudinal view, whenever practical.
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Tolerances
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Variation isUnavoidable No two manufactured objects
are identical in every way.Some deree of variationwill
exist.
Enineers a!!ly tolerancesto
!art dimensions to reduce t"e
amount of variation t"at
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#NSI$#S%E Standard
#NSI$#S%E Standard &'(.)
Each dimension shall have a tolerance,except those dimensions specifically
identified as reference, maximum,
minimum, or stock. The tolerance may be
applied directly to the dimension or
indicated by a general note located in the
title block of the drawing.
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Tolerances# toleranceis an
acce!tableamount of
dimensional
variation t"at willstill allow an
object to function
correctly.
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Tolerances# toleranceis an
acce!tableamount of
dimensional
variation t"at willstill allow an
object to function
correctly.
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Tolerances
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T"ree basic
tolerances t"at
occur most often
on wor*in
drawins are+ limit
dimensions,unilateral, and
bilateral tolerances.
Tolerances
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TolerancesT"ree basic
tolerances t"at
occur most often
on wor*in
drawins are+ limit
dimensions,unilateral, and
bilateral tolerances.
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LimitDimensionsLimit dimensionsare
two dimensional values
stac*ed on to! of eac"
ot"er. T"e dimensions
s"ow t"e larest and
smallest values allowed.#nyt"in in between
t"ese values is
acce!table.
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T"ese are limit dimensions,
because t"e u!!er andlower dimensional si-es are
stac*ed on to! of eac" ot"er.
LimitDimensions
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UnilateralTolerance#unilateral
toleranceexists
w"en a taret
dimension is iven
alon wit" a
tolerance t"at allowsvariation to occur in
only one direction.
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T"is tolerance is
unilateral, because
t"e si-e may only
deviate in one direction.
Unilateral
Tolerance
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ilateral
Tolerance#bilateral
toleranceexists if
t"e variation from a
taret dimension is
s"own occurrin in
bot" t"e !ositiveand neative
directions.
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If no tolerances are s!ecified at t"e
dimension level, t"en eneral tolerances
may be a!!lied by deliberately controllint"e number of values !ast t"e decimal
!oint on eac" dimension.
/eneral
Tolerances
Linear Dimensions
0.0 1 2 .343
0.00 1 2 .3'3
0.000 1 2 .33)
#nles 1 2 .)5
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/eneral
TolerancesTolerances
0.0 1 2 .343
0.00 1 2 .3'3
0.000 1 2 .33)
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T"e total tolerance is a value t"at
describes t"e maximum amount of
variation.Tolerance 1
.3'3
.)33
.343
.(63 .)'3Target Dimension
Total Tolerance
Total Tolerance 1 .
343
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# measurin device s"ould be able to
accurately measure wit"in '$'3t"of t"e
total blue!rint tolerance identified.
Total Tolerance
.)33
.343
.(63 .)'3Target Dimension
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Total tolerance =.!""
1.!x
"x =.! x =.!
In t"is case, a measurin device
s"ould be able to ta*e accuratemeasurements to wit"in two
t"ousandt"s of an inc".
Tolerances and
%easurin
0 1 t"e minimum
*hree *ypes of Cit
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*hree *ypes of Cit
*here are three types of fit that should beconsidered when working with tolerances.
'learance Cit! have limits of size so prescribed that aclearance always results when mating parts are
assembled. Interference Cit! have limits of size so prescribed that an
interference always results when mating parts areassembled.
*ransition Cit! have limits of size indicating that either a
clearance or an interference may result when matingparts are assembled.