GD&T - Print Reading for Manufacturing

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CHAPTER 11

Reading Geometric Dimensioning

and Tolerancing



Learning Objectives• Identify the ASME standard for

dimensioning and tolerancing

• Read prints containing geometricdimensioning applications

• Provide datum identification as given on

actual prints• Read datum target points, lines, area, and

related datum target symbols



Learning Objectives• Calculate the geometric tolerance at given

produced sizes based on the material

condition symbol• Read and explain the information given in

feature control frames presented on prints• Calculate the virtual condition for given

applications• Explain the purpose of geometric

tolerancing



Learning Objectives• Describe methods for representing datum

surfaces, datum target points, areas, lines,

datum center planes, and datum axes ondrawings• Identify the degrees of freedom of a part• Interpret drawing applications specifying

regardless of featuresize (RFS) and regardless

of material boundary (RMB), maximum materialcondition (MMC), and least material condition(LMC)



Learning Objectives• Interpret surface geometric controls and

axis geometric controls

• Read location tolerances on drawings

• Explain the differences betweenconventional tolerancing and positional

tolerancing• Interpret rectangular coordinate and polar

coordinate dimensioning on drawings



Learning Objectives• Read composite positional tolerances on

drawings

• Interpret geometric tolerances specified for threaded fasteners

• Read projected tolerance zonerepresentations on drawings

• Interpret concentricity geometrictolerances and positional tolerancesspecified for coaxial features on drawings



Learning Objectives• Read symmetry geometric tolerances and

positional tolerances specified for

symmetrical features on drawings• Read profile geometric tolerances on

drawings• Interpret runout geometric tolerances on

drawings• Interpret form tolerances when

independency is specified



Geometric Tolerancing• Geometric dimensioning and

tolerancing (GD&T)• Helps ensure interchangeability of parts

• Use dictated by function and

relationship of part feature• Does not take the place of

conventional tolerancing (Chapter 8)

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ASME GD&T Standards• ASME Y14.5 Dimensioning and Tolerancing• ASME Y14.5.1 Mathematical Definition of Dimensioning

and Tolerancing Principles

• ASME Y14.5.2 Certification of Geometric Dimensioningand Tolerancing Professionals

• ASME Y14.31 Undimensioned Drawings• ASME Y14.43 Dimensioning and Tolerancing Principles

for Gages and Fixtures

• ASME Y14.1 Decimal Inch Drawing Sheet Size andFormat

• ASME Y14.1M Metric Drawing Sheet Size and Format



GD&T Symbols• Five basic types:

– Dimensioning symbols – Datum feature and datum target symbols

– Geometric characteristic symbols

– Material condition symbols

– Feature control frame



Datums• Reference features of an object

– Planes

– Points

– Lines

– Axes

• The true geometric counterpart of adatum feature

• Establish location and size dimensions







Datum Feature Simulators• The opposite shape of the datum feature• Two types:

– Theoretical datum feature simulator – Physical datum feature simulator

• Manufacturing examples: – Machine tables

– Surface plates – Gauge surfaces – Surface tables – Rotation devices





Datum Feature Symbol• Drawn using thin lines

• Symbol size relates to the drawinglettering height

• Each datum feature is identified with a

different letter except I, O, and Q• Not applied to centerlines, center

planes, or axes



Datum Feature Symbol



Datum Feature Terms• Actual mating envelope

• Datum plane• Simulated datum

• Tangent plane



Datum Feature



DatumFeature

Symbol

Placement



Datum Surface• Can be controlled by a geometric

tolerance

• Measurements taken from a datum

plane do not take into account any

variations of the datum surface from the

datum plane



Geometric Control of DatumSurface



Datum Reference Frame(DRF)

• Used for layout purposes

• Selected by three datum features that areperpendicular to each other

• Assigned precedence and datumreference order: – Primary datum – Secondary datum – Tertiary datum




• All parts have six

degrees of freedom – Three degrees of

translation

– Three degrees of rotation

• Movement istranslational or rotational



Multiple Datum Reference Frames Example

• Datum reference X,

Y, and Z

• Datum reference L

and M



Datum Features SpecifiedIndividually

• A note appears next to datum feature

symbols indicating how many datumfeatures to consider separately

• The note “2X INDIVIDUALLY” appears

next to datum feature symbols of twoseparate datum features identified bysame letter



Reading Datum TargetSymbols

• Identify datum targets

• Useful on parts with surface or contour

irregularities

•Connect to datum target point, line, or area with a leader



Reading Datum Target Symbols• Movable datum target



Reading Datum Target Points• Primary datum plane is established by locating at

least three points on primary datum surface• Secondary datum plane is established by locating

at least two points on related secondary datumsurface

• Tertiary datum plane is established by locating atleast one point on related tertiary datum surface

• Dimensioned using baseline or chain dimensioning• Location dimensions originate from datums



Datum Target Point Locations• Use basic

dimensions or

tolerancedimensions



Datum Target Area Locations



Datum Target Line Locations



A Partial Datum Surface



Coplanar Datum Surfaces• Surfaces treated as a single, interrupted

surface

• Continuous feature symbol, or

• Note below the related feature control

frame



Coplanar Datum Surfaces



Datum Axis• A cylindrical object can be a datum feature• Represents two theoretical planes intersecting at

90°• Represented in drawings with centerlines• Pitch cylinder for screw threads establishes datum

axis unless otherwise specified – When not using pitch cylinder for screw threads, place

note such as "MAJOR DIA" or "MINOR DIA" next todatum feature symbol

• Simulated datum axis established by inspectionequipment



Datum Axis



Reading the Datum Feature Symbol for a

Datum Axis



Coaxial Datum Features• A single datum axis

is established by

two datum featuresthat are coaxial



Datum Axis Established withDatum Target Symbols

• Primary datum axis established by two

sets of three equally spaced targets• Datum target points identified in

correlation to adjacent cylindrical datum

feature when two cylindrical features of different diameters establish a datumaxis



Datum Axis Established withDatum Target Symbols

• Cylindrical datum target areas and circular datum

target lines can be used to establish datum axis – Target area represented by two phantom lines withsection lines between

– Datum target line represented by phantom line allaround part

• Secondary datum axis established by placing threeequally spaced targets on cylindrical surface



Movable Datum Target Symbolswith Datum Target Points

• When datum targets establish a center

point, axis, or center plane on a RMB

basis, datum feature simulator

movement is normal to true profile



Movable Datum Target Symbols with Datum

Target Points



Datum Center Plane• Axis and center plane datum feature

symbols align with/replace dimension

line arrowhead or appear on feature,

leader shoulder, dimension line, or

feature control frame



Datum Center Plane



Material Condition Symbols andMaterial Boundary Symbols

• Appear with geometric tolerance or

datum reference in feature control

frame

• Modify geometric tolerance in

relationship to actual produced size of feature




• Regardless of feature size (RFS) and

regardless of material boundary (RMB)

are assumed



Limits of Size Application



Perfect Form Boundary• Parts produced at MMC must be at

perfect form

• For a part at LMC, form tolerance can

vary within geometric tolerance zone to

extent of MMC boundary

• Independency symbol specifies that

perfect form at MMC is not required



Regardless of Feature Size(RFS) and Regardless of

Material Boundary (RMB)• Assumed when no material condition or

boundary condition symbol is specified

– RFS applies with respect to individual

geometric tolerance – RMB applies to datum reference



Regardless of Feature Size(RFS) and Regardless of

Material Boundary (RMB)• Circularity, cylindricity, profile, circular

runout, total runout, concentricity, andsymmetry are applied only on an RFSbasis

• Tolerance specified using RFS is held atany produced size within specifieddimensional tolerance



Surface Geometric Control,Regardless of Feature Size (RFS)

• RFS is implied if MMC or LMC is not

specified• Surface control is not associated with a

size dimension• Each longitudinal element of the surface

must lie between two parallel lines of thegeometric tolerance zone

• Perfect form boundary example



Axis Geometric Control,Regardless of Feature Size (RFS)

• Diameter symbol in front of the geometric

tolerance in the feature control framespecifies diameter tolerance zone



Reading Maximum MaterialCondition (MMC)

• Indicated maximum amount of material

for feature

– Maximum shaft diameter

– Minimum hole diameter

• Specified geometric tolerance is held

only at MMC produced size



Reading Maximum MaterialCondition (MMC)

• External feature formula:

– MMC – Produced Size + Given Geometric

Tolerance = Applied Geometric Tolerance

• Internal feature formula:

– (Produced Size – MMC) + GivenGeometric Tolerance = Applied Geometric

Tolerance



Axis Control, MaximumMaterial Condition (MMC)



Reading Least MaterialCondition (LMC)

• Indicates least amount of material for feature

– Minimum shaft diameter – Maximum hole diameter

• Given geometric tolerance is held at LMCproduced size

• No requirement for feature to maintain perfectform when produced at the LMC size limit



Reading Least MaterialCondition (LMC)

• External feature formula:

– Produced Size – LMC + Given Geometric

Tolerance = Applied Geometric Tolerance

• Internal feature formula:

– LMC – Produced Size + Given GeometricTolerance = Applied Geometric Tolerance



Reading Least Material Condition (LMC)



Application of RMB onPrimary Datum Feature

• RMB is implied for datum features influenced bysize and form variations unless otherwise specified

• When a datum feature has a size dimension andform tolerance, size of simulated datum is MMBsize limit – Boundary can exceed MMB when axis straightness is

specified

• For a datum feature of size, datum is establishedby contact between datum feature surface andsurface of processing equipment



Application of RMB onPrimary Datum Feature

• Simulated datum is axis of datum

feature simulator – External feature:

• Smallest circumscribed perfect cylinder thatcontacts datum feature surface

– Internal feature:• Largest inscribed perfect cylinder that contacts

datum feature surface



Application of RMB on aPrimary Datum Center Plane

• Simulated datum is center plane of

datum feature simulator

– External feature:

• Two parallel planes that contact datum feature

surface at minimum separation – Internal feature:

• Two parallel planes at maximum separation



RMB on a Secondary andTertiary Datum Feature

• Secondary

– Same guidelines for primary datum axis or center plane except:• Contacting datum feature simulator is 90°, or another design

angle, to primary datum, which is usually an adjacent plane

• Tertiary – Same guidelines for secondary datum axis or center

plane except:• Contacting datum feature simulator is 90°, or another design

angle, to primary and secondary datums



The Effect of Datum Precedenceand Material Condition

• Effect of material condition on datum

closely examined when precedence isassigned

– Changes in precedence alter part fit and

function



The Effect of Datum Precedenceand Material Condition



Geometric CharacteristicSymbols

• Provide specific controls related to the:

– Form of an object

– Orientation of features

– Outlines of features

– Relationship of features to an axis

– Location of features



Geometric Characteristic Symbols



The Feature Control FrameSymbol



Form Tolerances• Applied to single features or elements of

single features

• Not related to datums• Used to control:

– Straightness

–Flatness – Circularity

– Cylindricity



Straightness Tolerance – Applied to control surface or axis

straightness



Surface StraightnessTolerance

• Feature cannot exceed MMC envelope

and must maintain perfect form if actualsize is produced at MMC

• Otherwise, RFS applies and geometric

tolerance remains the same at anyproduced size



Axis Straightness• Fature control frame placed below

diameter dimension

• Diameter symbol placed in front of

geometric tolerance

• Allows a violation of perfect form at

MMC

• RFS assumed



Axis Straightness at MMC• MMC symbol appears after the geometric

tolerance

• Specified geometric tolerance held atMMC and can increase as actual sizedeparts from MMC

• Acceptance boundary can be used as afunctional gage to verify the part

• Local size is also verified



Unit Straightness• Specifies straightness per unit

• Prevents an abrupt surface variation

within a relatively short length of the

feature

• Tolerance over total length is greater

than unit tolerance



Unit Straightness• Per unit specification given per inch or

per 25 mm of length

• Derived axis or centerline of the actual

feature lies within a cylindrical tolerance

zone for:

– Total length

– Any 25 mm length, RFS



Straightness of Non-cylindricalFeatures

• Controls median plane of the part within specifiedstraightness tolerance

• Leader or extension line attaches feature controlframe to surface in a view where the surfaceappears as a line – Diameter symbol does not appear in front of geometric

tolerance

• Straightness of a rectangular part applies at RFS or MMC

• Generally appropriate for thin features



Straightness of a Flat Surface• Straightness geometric tolerance

controls single line elements on surface

in one or two directions

• Tolerance zone direction determined by

feature control frame placement



Flatness Tolerance• Establishes flatness

tolerance zone

– Always consideredRFS when applied to

a surface



Flatness Applied to a SizeDimension

• In a typical application, derived median

plane of feature lies within two parallelplanes spaced equal to specified

flatness geometric tolerance

• Geometric tolerance applied at RFS or MMC



Specific Area Flatness• Used when a large cast surface must be

flat in relatively small area –

Machine only required area• Specific area outlined with phantom lines – Section lines added within area

• Specific area located from datums with

basic or ± dimensions• Feature control frame connected to area

with leader line



Unit Flatness• Used alone or in combination with a total

tolerance

• Most applications use unit flatness with a totaltolerance over entire surface so the unit calloutdoes not become unmanageable

• Unit tolerance must be smaller than total

tolerance• Unit flatness specified using a square,rectangular, or circular unit area



Circularity Tolerance• Established from periphery, shaft

circumference, or inside diameter of a hole

• Does not reference a datum and is alwaysRFS

• Must be less than size tolerance

• Feature control frame connects to the viewwhere the feature appears as a circle or inthe longitudinal view



Circularity Tolerance



Circularity Tolerance for aSphere

• Established by two concentric circles

created by a plane passing through thesphere’s center

• All points on surface must lie within

circularity tolerance zone



Free State Variation Appliedto Circularity

• Typical in nonrigid parts

• Circularity specification of a nonrigidpart can be based on average diameter – Free state symbol appears in feature

control frame after geometric tolerance andmaterial condition symbol

– “AVG” placed after size dimension



Cylindricity Tolerance• Form tolerance not referenced to a

datum

• Geometric tolerance must be less than

size tolerance

• Always RFS

• Composite control of circularity,

straightness, and taper



Cylindricity Tolerance



Orientation GeometricTolerances

• Used to establish “total” control of

feature relationships: – Parallelism

– Perpendicularity

– Angularity – Profile (in some cases)



Orientation Tolerances• Controlled feature relates to one or more

datum features

• EACH ELEMENT or EACH RADIALELEMENT note allows for control of individual surface elements

• When tolerance is applied to a plane

surface, flatness is controlled to the extentof the orientation tolerance• RFS implied



Surface Parallelism• Requires parallelism

geometric tolerance• Actual surface must

be within parallelismtolerance zoneestablished by twoplanes parallel to thedatum

• Parallelism tolerancezone must be withinspecified size limits



Tangent Plane• Additional requirement applied to a surface

control

• Symbol placed after geometric tolerance infeature control frame

• Actual surface can be outside parallelismgeometric tolerance zone

• Tangent plane must be within parallelismgeometric tolerance zone



Axis Parallelism



Axis Parallelism• Can be applied to the axes of two or

more features

• Axis of feature must lie within cylindrical

tolerance zone parallel to datum axis

– Diameter tolerance zone

• RFS assumed unless applying MMC or

LMC



Parallelism of Line and RadialElements

• Place note EACH ELEMENT below feature

control frame to control only individual lineelements – Only controls elements in a plane parallel to view

in which the tolerance is given

•Note EACH RADIAL ELEMENT placed under feature control frame to control parallelism for individual line elements on a radial surface



Perpendicularity of a Surface• Requires perpendicularity tolerance• Always RFS

• Requires datum reference• Surface can be held perpendicular to one

datum plane or two datum planes – Surface held perpendicular to two datum

planes is between two parallel planesperpendicular to two datum planes – Feature control frame references both datums



Perpendicularity of an Axis• Established by two parallel planes

perpendicular to a datum plane or axis

within which the axis feature must lie

• Feature control frame appears below

diameter dimension

• Only applies in view where dimension is

shown



Perpendicularity of an Axis• RFS implied unless applying MMC or

LMC

• Cylindrical perpendicularity tolerance

zone applied when diameter symbol

appears in front of geometric tolerance

in feature control frame



Perpendicularity of a Center Plane

• Specifies symmetrical feature as

perpendicular to datum plane – Feature center plane held within two

parallel planes that are perpendicular to a

datum plane – Center plane must be within the specified

location tolerance



Perpendicularity of LineElements and Radial Elements• Note used when controlling individual line

elements of a surface: – EACH ELEMENT below feature control frame

• Note used when controlling individual line

elements of a radial surface: – EACH RADIAL ELEMENT under feature

control frame



Combining Parallelism andPerpendicularity

• Allows versatility by providing uniform

parallelism and perpendicularity to relateddatums

• Tolerance zones are different or same

• Feature control frames stacked to providefeature control frame compartment for each geometric tolerance



Angularity Tolerance• Angle must be basic

from the datum

plane• RFS implied unless

otherwise specified



Angularity of an Axis• Can be used to control feature axis

between two parallel planes

– Planes are spaced equally on each side of specified basic angle from datum plane or axis

– Axis of feature must lie within this zone

– Only applies to view where specified

– Feature control frame appears next to feature

diameter dimension to specify axis control



Angularity of an Axis• Can be used to control feature axis

within a cylindrical angularity tolerance

zone – Diameter symbol appears in front of

geometric tolerance in feature control

frame – Specifies cylindrical tolerance zone



Angularity of a Center Planeand Single Element Control

• Angularity tolerance formed by two parallel

planes at specified basic angle to datum plane• Center plane of feature must lie within this zone

• Used for single line element or single radialelement control

– Note EACH ELEMENT or EACH RADIALELEMENT placed below feature control frame



Zero Orientation Tolerance atMMC

• Can be used for parallelism,

perpendicularity, or angularity• Feature has perfect orientation at MMC



Location Tolerancing• Uses location tolerances

– Positional tolerance

– Concentricity tolerance

– Symmetry tolerance



Positional Tolerancing• Used to establish location of features

from true position

• Provides benefits over conventional

methods



Positional Tolerancing• Diameter symbol included when applied

to a cylindrical tolerance zone

– Compartments addedfor datum reference

– MMC or LMC symbol appears after

tolerance

– Assume RFS or RMB unless MMB or LMBsymbol follows specified datum reference



Positional Tolerancing• Establishes cylindrical tolerance zone

when applied to a cylindrical feature

• When applied to a noncylindrical

feature, tolerance value represents

distance between two parallel straight

lines or planes or distance between twouniform boundaries



Conventional Tolerancing• Establishes surface tolerance zone

– Uses ± or limit location dimensions

– Actual hole center is anywhere within the

square area

– Diagonal of zone is greatest distance that

allows variation in center location – Diagonal becomes diameter tolerance

zone cylindrical through thickness of part



Positional Tolerancing• Provides increase of 54% in permissible

area for the hole location

• Drawings converted from conventionaltolerancing

– Datums added

– Location dimensions changed from ± to basic – Feature control frame added to diameter

dimension



Positional Tolerance Zone• Hole axis at true

position

• Positional toleranceat MMC



Positional Tolerance Zone

• Hole axis at extreme positional variation

• Positional tolerance at MMC• Positional tolerance at MMC



Positional Tolerance Zone• Hole axis at extreme attitude variation

• Positional tolerance at MMC



Positional Tolerance at MMC• Tolerance increases equal to amount of

change from MMC

•Maximum positional tolerance occurs at LMC• Internal feature formula: – Actual Size – MMC + Specified Positional

Tolerance = Applied Positional Tolerance

• External feature formula: – MMC – Actual Size + Specified PositionalTolerance = Applied Positional Tolerance



Introduction to VirtualCondition

• Internal feature:

– MMC OF FEATURE – RELATEDGEOMETRIC TOLERANCE = VIRTUALCONDITION

• External feature:

– MMC OF FEATURE + RELATEDGEOMETRIC TOLERANCE = VIRTUALCONDITION



Positional Tolerance Based onthe Surface of a Hole

• All elements of hole surface must be

outside a theoretical boundary locatedat true position and produced within

specified size limits



Zero Positional Tolerancing atMMC

• Positional tolerance increases equal to

amount of departure as feature sizedeparts from MMC

• Total allowable variation in positional

tolerance is at LMC



Positional Tolerance at RFS• Assume RFS when no material

condition symbol appears after

positional tolerance• RFS applied to positional tolerance

when it is desirable to maintain givenpositional tolerance at any producedsize – RFS requires closer control of features



Positional Tolerance at LMC• Used to control relationship of feature

surface and true position of largest hole

size• Sometimes controls minimum edge

distance or minimum wall thickness

• Positional tolerance held at LMC



Positional Tolerance at LMC• Positional tolerance increases equal to

amount of change from LMC as

produced size departs from LMCtoward MMC

• Maximum positional tolerance is at

MMC• Requires perfect form at LMC



Calculating PositionalTolerance at LMC

• Internal feature:

– LMC – Actual Size + Specified PositionalTolerance = Applied Positional Tolerance

• External feature:

– Actual Size – LMC + Specified PositionalTolerance = Applied Positional Tolerance



Locating Multiple Features• Rectangular coordinate dimensioning

used in positional tolerancing

applications



Locating Multiple Features• Polar coordinate dimensioning used to

establish angular dimensions in

positional tolerancing applications



Single Composite Pattern

• Location dimensions

are basic from

datum referenceframe

• All holes checked

together



Positional Tolerance SpecifiedIndividually

• Used when a multiple datum reference frameexists and features are positioned to differentdatums individually

• Note appears next to datum feature symbolsand related feature control frame to identifyhow many datum features and positiontolerance specifications to consider individually – Example: 2X INDIVIDUALLY



Composite PositionalTolerance

• Feature control frame doubled in heightand divide into two parts – One positional geometric characteristic symbol

used in one double height feature controlframe compartment

– Pattern-locating control specified in upper part

of feature control frame – Feature-relating control specified in lower

entry



Composite Positional Tolerance



Two Single-Segment FeatureControl Frames• Two position symbols displayed, each in a

separate compartment – Pattern-locating control specified in top half of feature control frame

– Single datum reference in lower half of feature

control frame provides orientation – Double datum reference provides orientation

and alignment for feature-relating control



Two Single-Segment FeatureControl Frames• Offers tighter relationship of holes within

pattern• Pattern-locating zones and feature-

relating zones must remain same

distance from secondary datum



Two Single-Segment Feature Control Frames



Composite Positional Tolerancing Applied To Circular Patterns• Pattern-locating zones located using a basic

diameter and basic angle between features

– Oriented to specified datum reference frame• Feature-relating zones located partially or

totally within boundaries of pattern-locatingzones

– Held perpendicular to primary datum – Controlled as group by basic dimensions

• Feature axes must fall within both zones



Composite Positional Tolerancing Applied To Circular

Patterns



Two Single-Segment Tolerance Applied to Circular Patterns• Top half of feature control frame controls

location of features as a group to the datums

• Slot and tertiary datum added to pattern-locating control to provide orientation of thepattern of holes

•Lower portion of feature control frame controlspattern of features related to each other



Two Single-Segment Tolerance Applied to Circular

Patterns



Material Condition Requirements InComposite Positional Tolerancing• Composite and two single-segment

feature control frames must have samematerial condition

• Datums must be in same order of

precedence with same boundarycondition



Position Tolerancing of Coaxial Features• Used for features with a common axis

– Holes and counterbores

• When tolerance is same for both features,positional tolerance zone diameter is samefor both features relative to specifieddatums – Feature control frame appears below note to

specify hole and counterbore



Position Tolerancing of Coaxial Features• When different tolerances are applied to

coaxial features related to the same datumfeatures, separate feature control framesare used – One feature control frame appears under note

to specify hole size – Another feature control frame appears under

note to specify counterbore



Position Tolerancing of Coaxial Features• When tolerances control individual

counterbore-to-hole relationships relativeto different datum features, an additionalspecification is required – A note appears under the datum feature

symbol for the hole and under the feature

control frame for the counterbore to indicatenumber of places each applies on anindividual basis



Coaxial Positional Toleranceof Features in Alignment• Used for holes lying apart and in

alignment• Positional tolerance zone of holes

located by basic dimensions fromreferenced datums

• Each hole can be produced at anylocation within positional tolerance zone



Coaxial Positional Tolerance of Features in

Alignment



Position Tolerancing of Non-parallel Holes



Locating Slotted Features• Located to centers with basic

dimensions from datums

• When a greater positional tolerance isplaced on the length than on the width,

a feature control frame is added to the

length and width dimensions



Locating Slotted Features• When the positional tolerance is controlled

in relation to the feature surfaces, eachfeature is controlled by a theoreticalboundary – Size of each slot is within size limits and no

portion of surface can enter theoreticalboundary

– Feature control frame preceded with number of slots, such as 2X



Locating Slotted Features

• Boundary formula:

– MMC Length –

Positional

Tolerance =

Boundary Length

– MMC Width –

Positional

Tolerance =

Boundary Width



Applying PositionalTolerancing to Fasteners• Fasteners (Chapter 9)

• Thread symbol represents thread ondrawing

• Thread note provides thread specifications

• Unless otherwise specified, geometrictolerances apply to pitch diameter



A Projected Tolerance Zone Applied to a Print



Projected Tolerance Zone Representation First Option

S



Projected Tolerance Zone Representation Second

Option



Calculating Virtual Condition• Internal Feature Formula:

– MMC SIZE OF THE FEATURE –

RELATED GEOMETRIC TOLERANCE =VIRTUAL CONDITION

• External Feature Formula:

– MMC SIZE OF THE FEATURE +RELATED GEOMETRIC TOLERANCE =

VIRTUAL CONDITION



Concentricity Geometric Tolerance



Concentricity GeometricTolerance• Form irregularities of an actual feature can

make it difficult to establish location of median points – Finding median points requires analysis of

surface variations

– Runout or positional tolerancing used unless itis absolutely necessary to control medianpoints



Symmetry GeometricTolerance• Applied only on an RFS basis• Related datum reference applied only on

an RMB basis• Presents difficulty in inspecting median

points

• Positional tolerance locating symmetricalfeatures considered if symmetry is notrequired



Positional Tolerancing LocatingSymmetrical Features• Diameter symbol omitted in feature control

frame

• Positional tolerance zone is distancebetween two parallel planes equallydivided on each side of true position

• Material condition must accompanypositional tolerance – RFS assumed otherwise



Profile of a Line between Two Points



Profile of a Line All Around



Unilateral Profile of a Line• Unequally disposed symbol appears

after geometric tolerance in feature

control frame• Tolerance value repeated after

unequally disposed symbol when the

tolerance has material added to featureor part

Unilateral Profile of a Line



Unilateral Profile of a Line



Unilateral Profile of a Line• Tolerance value placed before the

unequally disposed symbol when the

tolerance has material taken from thefeature or part

• 0 appears after the unequally disposedsymbol

• Specifies entire profile tolerance isinside of true profile



Alternate Unilateral ProfileTolerance Option• Short phantom line appears parallel to

the true profile on the side of theintended unilateral tolerance

• Dimension line with an arrowheadplaced on the far side and a leader line

connected to the feature control framewith a leader line on the other side



Unequally Disposed Profile of a Line• Total profile tolerance value appears

before the unequally disposed symbolin feature control frame

• Value of tolerance that adds material to

the feature or part placed after theunequally disposed symbol

Unequally Disposed Profile of a Line



Unequally Disposed Profile of a Line



Alternate Unequally DisposedProfile Tolerance Option• Either inside or outside of true profile

shown as a basic dimension

• Dimension line with arrowheads placed oneach side of the phantom lines andconnected to the feature control frame witha leader

• Actual profile of part must be between thebasic zone created around the true profile



Profile of a Surface Tolerance• Use to control entire surface as a singlefeature

• Extends along total length and width or

circumference of object or feature(s) – Establishes a blanket tolerance

• Equally disposed bilateral unlessotherwise specified

• Normally requires reference to datums for proper orientation of profile

Profile of a Surface Between Two Points



Profile of a Surface Between Two Points



Profile of a Surface All Aroundor All Over • Establishes a blanket tolerance

• Surfaces all around or all over objectoutline must lie between two parallelboundaries equal in width to givengeometric tolerance

• Tolerance zone should beperpendicular to datum plane



Profile of a Sharp Corner • Tolerance zone extends to intersection

of the boundary lines

• A rounded corner can occur • Controlled using a maximum radius

note



Unilateral or UnequallyDisposed Profile of a Surface



Coplanar Profile Tolerance• Used to control profile of coplanar surfacesas a single surface

• Phantom line appears between surfaces in

the view where required surfaces appear as lines

• Leader connects from feature controlframe to phantom line and a note appears

below feature control frame identifying thenumber of surfaces



Coplanar Profile Tolerance



Profile of Plane Surfaces• Used to control form and orientation of

planar surfaces

• Can be used to control the angle of aninclined surface in relationship to a datum

– Surface must lie between two parallel planes

equally split on each side of a true plane that

has a basic angular orientation to a datum



Profile of Conical Features• Controls form or form and orientation

• Controls feature independently as a refinementof size or orients feature to a datum axis

• Profile tolerance must be within the sizetolerance

• Actual surface must lie between two coaxialboundaries equal in width to the specified

geometric tolerance, having a basic includedangle, and within the size limits



Composite Profile Tolerance• Feature control frame doubled in height• Geometric characteristic symbol placed in

first compartment

• Locating tolerance zone specified in tophalf of feature control frame – Datum reference given in order of precedence

in feature control frame

– Feature to be controlled from datums locatedwith basic dimensions



Composite Profile Tolerance• Profile form and orientation tolerance

zone specified in bottom half of feature

control frame – Datum referencing establishes limits of

size, form, and orientation of profile related

to locating tolerance zone

• Actual feature surface must be within

both tolerance zones

Profile of a Feature to Be



Profile of a Feature to Be

Restrained• Identify datum features

• Provide a note specifying process usedand force required to restrain the part



Runout Geometric Tolerance• Used to control surfaces constructed

around or perpendicular to a datum axis

– Control of circular elements of a surface – Control of cumulative variations of

circularity, straightness, coaxiality,

angularity, taper, and profile of a surface

– Control of variations in perpendicularity

and flatness



Runout Geometric Tolerance• Always specified RFS

• Datum references always specified RMB

• Feature control frame connects to surfaceby a leader line

• Multiple leaders used to direct a feature

control frame to two or more surfaceshaving a common runout tolerance



Circular Runout• Controls circularity and coaxiality when

applied to surfaces constructed around

or perpendicular to a datum axis• Can be used to control wobbling motion

• Controlling datum verified before

checking other surfaces• Reference datum always RMB



Circular Runout• Measured by full indicator movement (FIM)of a dial indicator placed at several circular measuring positions as part is rotated 360°

• FIM is a total tolerance• Each circular element must lie within the

FIM• Datum axis for runout inspection

estabished using a clamping device – Collet typical

Circular Runout



Circular Runout



Total Runout• Controls combined variations of circularity,straightness, coaxiality, angularity, taper, andprofile when applied to surfaces constructed

around and at right angles to a datum axis• Can control combined variations of

perpendicularity

• Can control concavity or convexity when

applied to surfaces perpendicular to a datumaxis



Total Runout



Total Runout

Runout Applied to a Portion of



Runout Applied to a Portion of

a Surface and Two Datum

References• Chain line located with basic dimensions

appears in linear view – Feature control frame connects to chain line

by a leader

• Datum identifying letters placed in feature

control frame• Letters separated by a dash

Runout Applied to a Datum



Runout Applied to a Datum

Surface and a Datum Axis• Datums placed separately in feature

control frame in order of precedence

• Profile must be within specifiedgeometric tolerance when part ismounted on the datum surface and

rotated 360° about the datum axis• Datum reference always specified RMB

Runout Control Applied to a



Runout Control Applied to a

Datum• Datum feature symbol specified to

apply runout• Datum feature symbol centered below

feature control frame or datum feature

symbol connected to the leader shoulder

Combining Runout with Other



Combining Runout with Other

Geometric Tolerances• Used in runout tolerancing applications

– Profile and circular runout – Runout and cylindricity



Specify Independency• Form control is independent of size

tolerance and should be added to the

feature• Size is verified by a two-point check

using a micrometer or caliper

GD&T - Print Reading for Manufacturing

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