howtospellgd&t

7/23/2019 HowtoSpellGD&T

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How to Spell GD&TA New Way to Learn GD&T

Thomas Allsup


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How Do You Spell GD&T?

GGeometric

DDimensioning&&

TTolerancing


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Why Are We Here?

Many will elie!e that a class on GeometricDimensioning an" Tolerances is li#e ta#ing high

school $nglish again%

Those people are ''( correct%

Learning GD&T is e)actly li#e learning a new

language%


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Tric#s?

Teaching people who "on*t want

to learn or thin# they "on*tnee" to is a "i++icult tas#%

Here*s some concepts that might

help you teach , learn GD&T%


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The Stan"ar"

ASM$ Y-%.M/00-

1-. per copy

A!ailale on 2D/34M

5ery similar to 6S4'%

$!erything we tal# aout this

morning is +rom the ASM$

stan"ar"%


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7483L?

There are - GD&T control symols%Normally these are groupe" y relate" an" unrelate"

+eatures%

Most GD&T lectures an" the ASM$ stan"ar" start with

8osition9 the most complicate" control an" then

procee" on to some o+ the simpler controls%

We will loo# at a techni:ue that 6 "e!elope" ase" on a

concept similar to the 8erio"ic Tale o+ $lements in2hemistry that groups the controls in a more logical

manner%


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8erio"ic Tale o+ $lements

2hemists groupelements toma#e pre"ictingnew elementseasier an" toallow othergeneralities%

We will ma#e useo+ a similargrouping +orGD&T%


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$lement 6n+ormation

In each element, the chart makers place information so

someone skilled in the arts will have all theinformation they need to work with the element.


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7483L 2hart

6 "e!elope"

this chart

a+ter training

se!eral

groups%

6t helps me to

this "ay an"

has helpe"

others%


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7483L Legen"

In each control, we place information so someoneskilled in the arts will have all the information they

need to work with the control.


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7i!e ;in"s o+ Geometric 2ontrol

All o+ these controls act


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7orm 2ontrols

7irst #in" o+ geometric control we loo# at is thesimplest= 7orm%

7orm control is D/D/>D/D /let*s see why%


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7ormStraightness

What geometry is two"imensional an" linear?

Answer= A straight line

Let*s call the control o+ astraight line9 the

ST3A6GHTN$SS%

The icon to represent astraight line woul" e a line=


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7orm7latness

What geometry is three"imensional an" linear?

Answer= A +lat plane

Let*s call the control o+ a +latplane9 the 7LATN$SS%

The icon to represent a +lat

plane woul" e the shape o+a plane=


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7orm2ircularity

What geometry is two"imensional an" rotary in

nature?

Answer= A circleLet*s call the control o+ a circle9

the 2632@LA36TY%

The icon to represent a circlewoul" e a circle=


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7orm2ylin"ricity

What geometry is three "imensional an" rotary

in nature?

Answer= A cylin"er

Some people want to guess sphere if

you look at tolerance zones, well seewhy cylinder is the correct answer.

Let*s call the control o+ a cylin"er9 the

2YL6ND3626TY%

The icon to represent a cylin"er shoul" e a

Beer canC ut instea" it is=

More on why this ma#es sense later%


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7orm 2allouts

>D

>D

D

D


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7483L6n 8rocess

We can cheat and see that there must beWe can cheat and see that there must be

three orientation controls.three orientation controls.


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4rientation 2ontrols

Secon" #in" o+ geometric control we loo# at is the ne)tsimplest= 4rientation%

4rientation control is


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4rientation Angles

When your arm is horiontal9 what is the angle it +orms

with the groun"?

Eero9 it is parallel with the groun"%

As you rotate you arm9 the angle is some aritrary

angle%When your arm in pointing up9 what is the angle it +orms

with the groun"?

Ninety "egrees9 it is perpen"icular with the groun"%Since the ground is our reference, lets call it aSince the ground is our reference, lets call it a

datum. Datums are very important to GDTdatum. Datums are very important to GDT

communication and represent an entire chapter ofcommunication and represent an entire chapter of

the standard. SolidWors users lie datums andthe standard. SolidWors users lie datums and

accept this mathematical concept easily.accept this mathematical concept easily.


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4rientation8arallelism

What orientation is at ero"egrees +rom the

re+erence?

8arallelismThe icon to represent when

things shoul" e parallel

woul" e a two parallellines=


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2ylin"ricity 3e!isite"

Two "imensional rotational +orm control

2ircularity plus 8arallel orientation o+ the

si"es e:uals three "imensional rotational

+orm control 2ylin"ricity%

6t #in" o+ all ma#es sense9 "oesn*t it?


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4rientationAngularity

What orientation is any angle?

Answer= Angularity

The icon to represent whentwo things are at an

aritrary angle loo#s li#e an

angle +rom your high school

geometry class=


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4rientation8erpen"icularity

What orientation is at ninety"egrees +rom the

re+erence?

Answer= 8erpen"icularity

The icon to represent when

things shoul" e

perpen"icular woul" e

something that loo#s li#e=


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4rientation 2allouts


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7483L6n 8rocess


t"o profile controls.t"o profile controls.


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8ro+ile 2ontrols

Now let*s start loo#ing at the complicate"geometric controls=

8ro+ile 2ontrols%

8ro+ile control is D/D%


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2omple) 8ro+iles?

Most people thin# o+ comple) shapes li#e the contouro+ a car ut the pro+ile can e as simple as a line or

circle%

6nspectors lo!e chec#ing pro+ile controlle" +eatures

ecause they can place a clear o!erlay on the+eature an" simply say pass or +ail%


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4ptical 2omparator

##Shado"Shado"

$graph%$graph%


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8ro+ile 2ontrolLine

We call the two "imensionalpro+ile control Bline profileC

or Bprofile of a lineC%

The line in :uestion cane any shape9 or anynumer o+ lines9 arcs9 orsplines%

The icon use" to represent

a line pro+ile is=Dont turn thatDont turn that

fro"n upsidefro"n upside

do"n!do"n!


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8ro+ile 2ontrolSur+ace

We call the three "imensionalpro+ile control Bsurface

profileC or Bprofile of a

surfaceC%

The sur+ace in :uestioncan e any shape9 or anynumer o+ planes or

sur+aces%The icon use" to represent a

sur+ace pro+ile is =


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8ro+ile 2allout


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7483L6n 8rocess


t"o runout controls as "ell.t"o runout controls as "ell.


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3unout 2ontrols

Let*s continue loo#ing at the complicate"geometric controls= 3unout 2ontrols%

3unout control is


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3unout 2ontrol2ircular

We call the two "imensional runoutcontrol Bcircular runoutC%

The icon use" to represent circular

runout is= Note this symol loo#s li#e the

nee"le +rom a "ial in"icator an"

that*s e)actly how we measure it%

3 2 l


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3unout 2ontrolTotal

We call the three"imensional runout

control Btotal runoutC%

This is a per+ect time total# aout what we call

the rotation o+ the "ial

in"icator o!er a +eature%

The icon use" to represent

total runout is=


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To 7ill or Not to 7illF

The ASM$ Y-%.M stan"ar" says the arrow hea"s +or can e +ille" or un+ille"

"epen"ing upon the 2AD system or +ont you wish to use%


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3unout 2allout

7483L


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7483L6n 8rocess

o" many location controls are there)o" many location controls are there)


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Location 2ontrols

The last #in" o+ geometric control we loo# at is the mostcomplicate"= Location%

Location control is


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Location8osition

The o!ious location control +or+eatures is position%

The icon to represent where a

+eature shoul" e9 we use atarget symol=

his reminds me of one of myfavorite military sayings!

-echanical engineers build-echanical engineers build"eapons."eapons.

ivil engineers build targets.ivil engineers build targets.

L ti


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LocationSymmetry

The +irst non/o!ious location controlis calle" symmetry%

The icon to represent when two

things shoul" e symmetric is=

Note the icon shows a mirrorre+erence line the "atum an"two little symmetric lines%

+ have never placed a symmetric tolerance+ have never placed a symmetric toleranceon a dra"ing or checed a dra"ing that hadon a dra"ing or checed a dra"ing that had

it /correct0. enterlines are another matter.it /correct0. enterlines are another matter.

aving said that, this is a po"erful setchaving said that, this is a po"erful setch

constraint in SolidWors 1 eep using it!constraint in SolidWors 1 eep using it!

Location


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Location2oncentricity

The secon" non/o!ious locationcontrol is calle" concentricity%

Most GD&T newies lo!e hearing aout

this symol an" are an)ious to use it

although they proaly shoul" eusing runout

2oncentricity is har" to inspect%

The icon to represent when two things

shoul" ha!e the same center a)is is=

To mae matters "orse, this is theTo mae matters "orse, this is the

assembly constraint in SolidWors forassembly constraint in SolidWors for

revolved elements!revolved elements!


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8osition 2allout

7483L


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7483L6n 8rocess

7483L L "


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7483L Legen"

In each control, we place information so someoneskilled in the arts will have all the information they

need to work with the control.

7483L Legen"


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7483L Legen"2

Tolerance ones are y "e+ault either Btotal wi"eC or

B+ull in"icator mo!ementC ut some Btotal wi"eC

tolerance ones can e change" to Bcylin"ricalC%

We*ll lea!e this area o+ the 7483L chart lan# e)cept

+or the controls that can ha!e cylin"rical tolerance

one an" then we*ll put=

7483L Legen"


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7483L Legen"D

Three options:

Datums not allowe"

Datums re:uire"

Datums are allowe" ut not re:uire" is


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7483L Legen"E

Ietween two cylin"ers

Within a cylin"er

Within a sphere

7ull 6n"icator

Mo!ement

Ietween two lines

Ietween twoplanes

Ietween two

cur!es

Ietween twocur!e" sur+aces

Ietween two circles

7483L Legen"


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7483L Legen"A

$!eryone turn in your stan"ar" to pagenumer F

2ntil you have a standard, youll 3ust to2ntil you have a standard, youll 3ust totrust me.trust me.

7483L Legen"


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7483L Legen"


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The 2omplete 7483L 2hart

Soli"Wor#s 8art Datums


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Soli"Wor#s J 8art Datums

Soli"Wor#s 8art 7eature 2ontrol 7rames


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Soli"Wor#s / 8art 7eature 2ontrol 7rames

Soli"Wor#s Drawing Datums


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Soli"Wor#s / Drawing Datums

Soli"Wor#s Drawing 7eature 2ontrol 7rames


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Soli"Wor#s/Drawing 7eature 2ontrol 7rames

2AD,2AM Data


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2AD,2AM Data

Section 2.1:BIf CAD/CAM database models are used and they do not

include tolerances, then tolerances must be

expressed outside of the database to reflect design

requirements.C

This section clearly states that models maymay

include tolerances hence paving the way to

eliminating conventional drawings someday!


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