dimensioning standard

7/24/2019 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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&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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*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


9/100

&imension $ines

2orizontal

Aligned to a slanted

surfaced

7ertical

0hen stacked, they

are -mm 8.95: fromthe view and

4mm8.;


10/100

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.


15/100

&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.


16/100

&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



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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.


86/100

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.


90/100

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.


91/100

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.


93/100

T"is tolerance is

unilateral, because

t"e si-e may only

deviate in one direction.

Unilateral

Tolerance


94/100

ilateral

Tolerance#bilateral

toleranceexists if

t"e variation from a

taret dimension is

s"own occurrin in

bot" t"e !ositiveand neative

directions.


95/100

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


96/100

/eneral

TolerancesTolerances

0.0 1 2 .343

0.00 1 2 .3'3

0.000 1 2 .33)


97/100

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


98/100

# 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


99/100

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


100/100

*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.

dimensioning standard

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