CHAPTER 11Reading Geometric Dimensioning and TolerancingLearning ObjectivesIdentify the ASME standard for dimensioning and tolerancingRead prints containing geometric dimensioning applicationsProvide datum identification as given on actual printsRead datum target points, lines, area, and related datum target symbolsLearning ObjectivesCalculate the geometric tolerance at given produced sizes based on the material condition symbolRead and explain the information given in feature control frames presented on printsCalculate the virtual condition for given applicationsExplain the purpose of geometric tolerancingLearning ObjectivesDescribe methods for representing datum surfaces, datum target points, areas, lines, datum center planes, and datum axes on drawingsIdentify the degrees of freedom of a partInterpret drawing applications specifying regardless of featuresize (RFS) and regardless of material boundary (RMB), maximum material condition (MMC), and least material condition (LMC)Learning ObjectivesInterpret surface geometric controls and axis geometric controlsRead location tolerances on drawingsExplain the differences between conventional tolerancing and positional tolerancingInterpret rectangular coordinate and polar coordinate dimensioning on drawingsLearning ObjectivesRead composite positional tolerances on drawingsInterpret geometric tolerances specified for threaded fastenersRead projected tolerance zone representations on drawingsInterpret concentricity geometric tolerances and positional tolerances specified for coaxial features on drawingsLearning ObjectivesRead symmetry geometric tolerances and positional tolerances specified for symmetrical features on drawingsRead profile geometric tolerances on drawingsInterpret runout geometric tolerances on drawingsInterpret form tolerances when independency is specifiedGeometric TolerancingGeometric dimensioning and tolerancing (GD&T)Helps ensure interchangeability of partsUse dictated by function and relationship of part featureDoes not take the place of conventional tolerancing (Chapter 8)ASME GD&T StandardsASME Y14.5 Dimensioning and TolerancingASME Y14.5.1 Mathematical Definition of Dimensioning and Tolerancing PrinciplesASME Y14.5.2 Certification of Geometric Dimensioning and Tolerancing ProfessionalsASME Y14.31 Undimensioned DrawingsASME Y14.43 Dimensioning and Tolerancing Principles for Gages and FixturesASME Y14.1 Decimal Inch Drawing Sheet Size and FormatASME Y14.1M Metric Drawing Sheet Size and FormatGD&T SymbolsFive basic types:Dimensioning symbolsDatum feature and datum target symbolsGeometric characteristic symbolsMaterial condition symbolsFeature control frameDatumsReference features of an objectPlanesPointsLinesAxesThe true geometric counterpart of a datum featureEstablish location and size dimensionsDatum Feature SimulatorsThe opposite shape of the datum featureTwo types:Theoretical datum feature simulatorPhysical datum feature simulatorManufacturing examples:Machine tablesSurface platesGauge surfacesSurface tablesRotation devicesDatum Feature SymbolDrawn using thin linesSymbol size relates to the drawing lettering heightEach datum feature is identified with a different letter except I, O, and QNot applied to centerlines, center planes, or axesDatum Feature Symbol

Datum Feature TermsActual mating envelopeDatum planeSimulated datumTangent planeDatum Feature

Datum Feature Symbol Placement

Datum SurfaceCan be controlled by a geometric toleranceMeasurements taken from a datum plane do not take into account any variations of the datum surface from the datum planeGeometric Control of Datum Surface

Datum Reference Frame (DRF)Used for layout purposesSelected by three datum features that are perpendicular to each otherAssigned precedence and datum reference order:Primary datumSecondary datumTertiary datumDatum Reference Frame (DRF)

Datum Reference Frame (DRF)All parts have six degrees of freedomThree degrees of translationThree degrees of rotationMovement is translational or rotational

Multiple Datum Reference Frames ExampleDatum reference X, Y, and ZDatum reference L and M

Datum Features Specified IndividuallyA note appears next to datum feature symbols indicating how many datum features to consider separatelyThe note 2X INDIVIDUALLY appears next to datum feature symbols of two separate datum features identified by same letterReading Datum Target SymbolsIdentify datum targetsUseful on parts with surface or contour irregularitiesConnect to datum target point, line, or area with a leaderReading Datum Target SymbolsMovable datum target

Reading Datum Target PointsPrimary datum plane is established by locating at least three points on primary datum surfaceSecondary datum plane is established by locating at least two points on related secondary datum surfaceTertiary datum plane is established by locating at least one point on related tertiary datum surfaceDimensioned using baseline or chain dimensioningLocation dimensions originate from datumsDatum Target Point LocationsUse basic dimensions or tolerance dimensions

Datum Target Area Locations

Datum Target Line Locations

A Partial Datum Surface

Coplanar Datum SurfacesSurfaces treated as a single, interrupted surfaceContinuous feature symbol, orNote below the related feature control frameCoplanar Datum Surfaces

Datum AxisA cylindrical object can be a datum featureRepresents two theoretical planes intersecting at 90Represented in drawings with centerlinesPitch cylinder for screw threads establishes datum axis unless otherwise specifiedWhen not using pitch cylinder for screw threads, place note such as "MAJOR DIA" or "MINOR DIA" next to datum feature symbolSimulated datum axis established by inspection equipmentDatum Axis

Reading the Datum Feature Symbol for a Datum Axis

Coaxial Datum FeaturesA single datum axis is established by two datum features that are coaxial

Datum Axis Established with Datum Target SymbolsPrimary datum axis established by two sets of three equally spaced targetsDatum target points identified in correlation to adjacent cylindrical datum feature when two cylindrical features of different diameters establish a datum axisDatum Axis Established with Datum Target SymbolsCylindrical datum target areas and circular datum target lines can be used to establish datum axisTarget area represented by two phantom lines with section lines betweenDatum target line represented by phantom line all around partSecondary datum axis established by placing three equally spaced targets on cylindrical surfaceMovable Datum Target Symbols with Datum Target PointsWhen datum targets establish a center point, axis, or center plane on a RMB basis, datum feature simulator movement is normal to true profileMovable Datum Target Symbols with Datum Target Points

Datum Center PlaneAxis and center plane datum feature symbols align with/replace dimension line arrowhead or appear on feature, leader shoulder, dimension line, or feature control frameDatum Center Plane

Material Condition Symbols and Material Boundary SymbolsAppear with geometric tolerance or datum reference in feature control frameModify geometric tolerance in relationship to actual produced size of featureMaterial Condition Symbols and Material Boundary Symbols

Material Condition Symbols and Material Boundary SymbolsRegardless of feature size (RFS) and regardless of material boundary (RMB) are assumed

Limits of Size Application

Perfect Form BoundaryParts produced at MMC must be at perfect formFor a part at LMC, form tolerance can vary within geometric tolerance zone to extent of MMC boundaryIndependency symbol specifies that perfect form at MMC is not requiredPerfect Form Boundary

Regardless of Feature Size (RFS) and Regardless of Material Boundary (RMB)Assumed when no material condition or boundary condition symbol is specifiedRFS applies with respect to individual geometric toleranceRMB applies to datum referenceRegardless of Feature Size (RFS) and Regardless of Material Boundary (RMB)Circularity, cylindricity, profile, circular runout, total runout, concentricity, and symmetry are applied only on an RFS basisTolerance specified using RFS is held at any produced size within specified dimensional toleranceSurface Geometric Control, Regardless of Feature Size (RFS)RFS is implied if MMC or LMC is not specifiedSurface control is not associated with a size dimensionEach longitudinal element of the surface must lie between two parallel lines of the geometric tolerance zone Perfect form boundary exampleAxis Geometric Control, Regardless of Feature Size (RFS)Diameter symbol in front of the geometric tolerance in the feature control frame specifies diameter tolerance zone

Reading Maximum Material Condition (MMC)Indicated maximum amount of material for featureMaximum shaft diameterMinimum hole diameterSpecified geometric tolerance is held only at MMC produced sizeReading Maximum Material Condition (MMC)External feature formula:MMC Produced Size + Given Geometric Tolerance = Applied Geometric ToleranceInternal feature formula:(Produced Size MMC) + Given Geometric Tolerance = Applied Geometric ToleranceAxis Control, Maximum Material Condition (MMC)

Reading Least Material Condition (LMC)Indicates least amount of material for featureMinimum shaft diameterMaximum hole diameterGiven geometric tolerance is held at LMC produced sizeNo requirement for feature to maintain perfect form when produced at the LMC size limitReading Least Material Condition (LMC)External feature formula:Produced Size LMC + Given Geometric Tolerance = Applied Geometric ToleranceInternal feature formula:LMC Produced Size + Given Geometric Tolerance = Applied Geometric ToleranceReading Least Material Condition (LMC)

Application of RMB on Primary Datum FeatureRMB is implied for datum features influenced by size and form variations unless otherwise specifiedWhen a datum feature has a size dimension and form tolerance, size of simulated datum is MMB size limitBoundary can exceed MMB when axis straightness is specifiedFor a datum feature of size, datum is established by contact between datum feature surface and surface of processing equipmentApplication of RMB on Primary Datum FeatureSimulated datum is axis of datum feature simulatorExternal feature:Smallest circumscribed perfect cylinder that contacts datum feature surfaceInternal feature:Largest inscribed perfect cylinder that contacts datum feature surfaceApplication of RMB on a Primary Datum Center PlaneSimulated datum is center plane of datum feature simulatorExternal feature:Two parallel planes that contact datum feature surface at minimum separationInternal feature:Two parallel planes at maximum separationRMB on a Secondary and Tertiary Datum FeatureSecondarySame 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 planeTertiarySame 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 Precedence and Material ConditionEffect of material condition on datum closely examined when precedence is assignedChanges in precedence alter part fit and functionThe Effect of Datum Precedence and Material Condition

Geometric Characteristic SymbolsProvide specific controls related to the:Form of an objectOrientation of featuresOutlines of featuresRelationship of features to an axisLocation of featuresGeometric Characteristic Symbols

The Feature Control Frame Symbol

Form TolerancesApplied to single features or elements of single featuresNot related to datumsUsed to control:StraightnessFlatnessCircularityCylindricityStraightness ToleranceApplied to control surface or axis straightness Surface Straightness ToleranceFeature cannot exceed MMC envelope and must maintain perfect form if actual size is produced at MMCOtherwise, RFS applies and geometric tolerance remains the same at any produced sizeAxis StraightnessFature control frame placed below diameter dimensionDiameter symbol placed in front of geometric toleranceAllows a violation of perfect form at MMCRFS assumedAxis Straightness at MMCMMC symbol appears after the geometric toleranceSpecified geometric tolerance held at MMC and can increase as actual size departs from MMCAcceptance boundary can be used as a functional gage to verify the partLocal size is also verifiedUnit StraightnessSpecifies straightness per unitPrevents an abrupt surface variation within a relatively short length of the featureTolerance over total length is greater than unit toleranceUnit StraightnessPer unit specification given per inch or per 25 mm of lengthDerived axis or centerline of the actual feature lies within a cylindrical tolerance zone for:Total lengthAny 25 mm length, RFS Straightness of Non-cylindrical FeaturesControls median plane of the part within specified straightness toleranceLeader or extension line attaches feature control frame to surface in a view where the surface appears as a lineDiameter symbol does not appear in front of geometric toleranceStraightness of a rectangular part applies at RFS or MMCGenerally appropriate for thin featuresStraightness of a Flat SurfaceStraightness geometric tolerance controls single line elements on surface in one or two directionsTolerance zone direction determined by feature control frame placementStraightness of a Limited LengthStraightness applied to a portion of a long part using a chain line next to view at desired straightness lengthDimension length of chain lineFeature control frame connected to chain line with a leaderApplied to a cylindrical or flat partFlatness ToleranceEstablishes flatness tolerance zoneAlways considered RFS when applied to a surface

Flatness Applied to a Size DimensionIn a typical application, derived median plane of feature lies within two parallel planes spaced equal to specified flatness geometric toleranceGeometric tolerance applied at RFS or MMCSpecific Area FlatnessUsed when a large cast surface must be flat in relatively small areaMachine only required areaSpecific area outlined with phantom linesSection lines added within areaSpecific area located from datums with basic or dimensionsFeature control frame connected to area with leader lineUnit FlatnessUsed alone or in combination with a total toleranceMost applications use unit flatness with a total tolerance over entire surface so the unit callout does not become unmanageableUnit tolerance must be smaller than total toleranceUnit flatness specified using a square, rectangular, or circular unit areaCircularity ToleranceEstablished from periphery, shaft circumference, or inside diameter of a holeDoes not reference a datum and is always RFSMust be less than size toleranceFeature control frame connects to the view where the feature appears as a circle or in the longitudinal viewCircularity Tolerance

Circularity Tolerance for a SphereEstablished by two concentric circles created by a plane passing through the spheres centerAll points on surface must lie within circularity tolerance zoneFree State Variation Applied to CircularityTypical in nonrigid partsCircularity specification of a nonrigid part can be based on average diameterFree state symbol appears in feature control frame after geometric tolerance and material condition symbolAVG placed after size dimensionCylindricity ToleranceForm tolerance not referenced to a datumGeometric tolerance must be less than size toleranceAlways RFSComposite control of circularity, straightness, and taperCylindricity Tolerance

Orientation Geometric TolerancesUsed to establish total control of feature relationships:ParallelismPerpendicularityAngularityProfile (in some cases)Orientation TolerancesControlled feature relates to one or more datum featuresEACH ELEMENT or EACH RADIAL ELEMENT note allows for control of individual surface elementsWhen tolerance is applied to a plane surface, flatness is controlled to the extent of the orientation toleranceRFS impliedSurface ParallelismRequires parallelism geometric toleranceActual surface must be within parallelism tolerance zone established by two planes parallel to the datumParallelism tolerance zone must be within specified size limits

Tangent PlaneAdditional requirement applied to a surface controlSymbol placed after geometric tolerance in feature control frameActual surface can be outside parallelism geometric tolerance zoneTangent plane must be within parallelism geometric tolerance zoneAxis ParallelismApplied for a feature axis by establishing two parallel planes parallel to a datum plane between which the axis must lieParallelism tolerance zone must be within specified location toleranceFeature control frame appears with diameter dimensionDiameter dimension associates the related geometric tolerance with feature axisRFS assumedAxis Parallelism

Axis ParallelismCan be applied to the axes of two or more featuresAxis of feature must lie within cylindrical tolerance zone parallel to datum axisDiameter tolerance zoneRFS assumed unless applying MMC or LMCParallelism of Line and Radial ElementsPlace note EACH ELEMENT below feature control frame to control only individual line elementsOnly controls elements in a plane parallel to view in which the tolerance is givenNote EACH RADIAL ELEMENT placed under feature control frame to control parallelism for individual line elements on a radial surfacePerpendicularity of a SurfaceRequires perpendicularity toleranceAlways RFSRequires datum referenceSurface can be held perpendicular to one datum plane or two datum planesSurface held perpendicular to two datum planes is between two parallel planes perpendicular to two datum planesFeature control frame references both datumsPerpendicularity of an AxisEstablished by two parallel planes perpendicular to a datum plane or axis within which the axis feature must lieFeature control frame appears below diameter dimensionOnly applies in view where dimension is shownPerpendicularity of an AxisRFS implied unless applying MMC or LMCCylindrical perpendicularity tolerance zone applied when diameter symbol appears in front of geometric tolerance in feature control framePerpendicularity of a Center PlaneSpecifies symmetrical feature as perpendicular to datum planeFeature center plane held within two parallel planes that are perpendicular to a datum planeCenter plane must be within the specified location tolerancePerpendicularity of Line Elements and Radial ElementsNote used when controlling individual line elements of a surface:EACH ELEMENT below feature control frameNote used when controlling individual line elements of a radial surface:EACH RADIAL ELEMENT under feature control frameCombining Parallelism and PerpendicularityAllows versatility by providing uniform parallelism and perpendicularity to related datumsTolerance zones are different or sameFeature control frames stacked to provide feature control frame compartment for each geometric toleranceAngularity ToleranceAngle must be basic from the datum planeRFS implied unless otherwise specified

Angularity of an AxisCan be used to control feature axis between two parallel planesPlanes are spaced equally on each side of specified basic angle from datum plane or axisAxis of feature must lie within this zoneOnly applies to view where specifiedFeature control frame appears next to feature diameter dimension to specify axis controlAngularity of an AxisCan be used to control feature axis within a cylindrical angularity tolerance zoneDiameter symbol appears in front of geometric tolerance in feature control frameSpecifies cylindrical tolerance zoneAngularity of a Center Plane and Single Element ControlAngularity tolerance formed by two parallel planes at specified basic angle to datum planeCenter plane of feature must lie within this zoneUsed for single line element or single radial element controlNote EACH ELEMENT or EACH RADIAL ELEMENT placed below feature control frameZero Orientation Tolerance at MMCCan be used for parallelism, perpendicularity, or angularityFeature has perfect orientation at MMCLocation TolerancingUses location tolerancesPositional toleranceConcentricity toleranceSymmetry tolerancePositional TolerancingUsed to establish location of features from true positionProvides benefits over conventional methodsPositional TolerancingDiameter symbol included when applied to a cylindrical tolerance zoneCompartments addedfor datum referenceMMC or LMC symbol appears after toleranceAssume RFS or RMB unless MMB or LMB symbol follows specified datum referencePositional TolerancingEstablishes cylindrical tolerance zone when applied to a cylindrical featureWhen applied to a noncylindrical feature, tolerance value represents distance between two parallel straight lines or planes or distance between two uniform boundariesConventional TolerancingEstablishes surface tolerance zoneUses or limit location dimensionsActual hole center is anywhere within the square areaDiagonal of zone is greatest distance that allows variation in center locationDiagonal becomes diameter tolerance zone cylindrical through thickness of partPositional TolerancingProvides increase of 54% in permissible area for the hole locationDrawings converted from conventional tolerancingDatums addedLocation dimensions changed from to basicFeature control frame added to diameter dimensionPositional Tolerance ZoneHole axis at true positionPositional tolerance at MMC

Positional Tolerance ZoneHole axis at extreme positional variationPositional tolerance at MMCPositional tolerance at MMCPositional Tolerance ZoneHole axis at extreme attitude variationPositional tolerance at MMCPositional Tolerance ZoneHole axis at true positionPositional tolerance at LMCPositional Tolerance at MMCTolerance increases equal to amount of change from MMCMaximum positional tolerance occurs at LMCInternal feature formula:Actual Size MMC + Specified Positional Tolerance = Applied Positional ToleranceExternal feature formula:MMC Actual Size + Specified Positional Tolerance = Applied Positional ToleranceIntroduction to Virtual ConditionInternal feature:MMC OF FEATURE RELATED GEOMETRIC TOLERANCE = VIRTUAL CONDITIONExternal feature:MMC OF FEATURE + RELATED GEOMETRIC TOLERANCE = VIRTUAL CONDITIONPositional Tolerance Based on the Surface of a HoleAll elements of hole surface must be outside a theoretical boundary located at true position and produced within specified size limitsZero Positional Tolerancing at MMCAllows positional tolerance zone to exceed amount specified when feature is produced at any actual size other than MMCSpecifies importance of certainty that tolerance is totally dependent on actual size of featureTrue position required at MMCZero Positional Tolerancing at MMCPositional tolerance increases equal to amount of departure as feature size departs from MMCTotal allowable variation in positional tolerance is at LMCPositional Tolerance at RFSAssume RFS when no material condition symbol appears after positional toleranceRFS applied to positional tolerance when it is desirable to maintain given positional tolerance at any produced sizeRFS requires closer control of featuresPositional Tolerance at LMCUsed to control relationship of feature surface and true position of largest hole sizeSometimes controls minimum edge distance or minimum wall thicknessPositional tolerance held at LMCPositional Tolerance at LMCPositional tolerance increases equal to amount of change from LMC as produced size departs from LMC toward MMCMaximum positional tolerance is at MMCRequires perfect form at LMCCalculating Positional Tolerance at LMCInternal feature:LMC Actual Size + Specified Positional Tolerance = Applied Positional ToleranceExternal feature:Actual Size LMC + Specified Positional Tolerance = Applied Positional ToleranceLocating Multiple FeaturesRectangular coordinate dimensioning used in positional tolerancing applications

Locating Multiple FeaturesPolar coordinate dimensioning used to establish angular dimensions in positional tolerancing applications

Single Composite PatternLocation dimensions are basic from datum reference frameAll holes checked together

Features in Patterns with Separate RequirementsTo treat patterns separately with regard to the datum references, the note "SEP REQT" appears below each feature control frameAppropriate when features in one pattern are different in size or have different location requirements than the features in other patternsPositional Tolerance Specified IndividuallyUsed when a multiple datum reference frame exists and features are positioned to different datums individuallyNote appears next to datum feature symbols and related feature control frame to identify how many datum features and position tolerance specifications to consider individuallyExample: 2X INDIVIDUALLYComposite Positional ToleranceFeature control frame doubled in height and divide into two partsOne positional geometric characteristic symbol used in one double height feature control frame compartmentPattern-locating control specified in upper part of feature control frameFeature-relating control specified in lower entryComposite Positional Tolerance

Two Single-Segment Feature Control FramesTwo position symbols displayed, each in a separate compartmentPattern-locating control specified in top half of feature control frameSingle datum reference in lower half of feature control frame provides orientationDouble datum reference provides orientation and alignment for feature-relating controlTwo Single-Segment Feature Control FramesOffers tighter relationship of holes within patternPattern-locating zones and feature-relating zones must remain same distance from secondary datumTwo Single-Segment Feature Control Frames

Composite Positional Tolerancing Applied To Circular PatternsPattern-locating zones located using a basic diameter and basic angle between featuresOriented to specified datum reference frameFeature-relating zones located partially or totally within boundaries of pattern-locating zonesHeld perpendicular to primary datumControlled as group by basic dimensionsFeature axes must fall within both zonesComposite Positional Tolerancing Applied To Circular Patterns

Two Single-Segment Tolerance Applied to Circular PatternsTop half of feature control frame controls location of features as a group to the datumsSlot and tertiary datum added to pattern-locating control to provide orientation of the pattern of holesLower portion of feature control frame controls pattern of features related to each otherTwo Single-Segment Tolerance Applied to Circular Patterns

Material Condition Requirements In Composite Positional TolerancingComposite and two single-segment feature control frames must have same material conditionDatums must be in same order of precedence with same boundary conditionPosition Tolerancing of Coaxial FeaturesUsed for features with a common axisHoles and counterboresWhen tolerance is same for both features, positional tolerance zone diameter is same for both features relative to specified datumsFeature control frame appears below note to specify hole and counterborePosition Tolerancing of Coaxial FeaturesWhen different tolerances are applied to coaxial features related to the same datum features, separate feature control frames are usedOne feature control frame appears under note to specify hole sizeAnother feature control frame appears under note to specify counterborePosition Tolerancing of Coaxial FeaturesWhen tolerances control individual counterbore-to-hole relationships relative to different datum features, an additional specification is requiredA note appears under the datum feature symbol for the hole and under the feature control frame for the counterbore to indicate number of places each applies on an individual basisCoaxial Positional Tolerance of Features in AlignmentUsed for holes lying apart and in alignmentPositional tolerance zone of holes located by basic dimensions from referenced datumsEach hole can be produced at any location within positional tolerance zoneCoaxial Positional Tolerance of Features in Alignment

Position Tolerancing of Non-parallel Holes

Locating Slotted FeaturesLocated to centers with basic dimensions from datumsWhen a greater positional tolerance is placed on the length than on the width, a feature control frame is added to the length and width dimensionsLocating Slotted FeaturesBidirectional positional tolerance used for a greater location tolerance in one direction than the other directionPositional tolerance results in a rectangular tolerance zoneOmit diameter symbol omited from the feature control framePositional tolerance zone is noncylindricalLocating Slotted FeaturesWhen the positional tolerance is controlled in relation to the feature surfaces, each feature is controlled by a theoretical boundarySize of each slot is within size limits and no portion of surface can enter theoretical boundaryFeature control frame preceded with number of slots, such as 2XLocating Slotted FeaturesBoundary formula:MMC Length Positional Tolerance = Boundary LengthMMC Width Positional Tolerance = Boundary Width

Position Tolerancing of Spherical FeaturesSpherical diameter symbol precedes feature size dimensionFeature control frame appears below size dimension and positional tolerance zone is spherical Applying Positional Tolerancing to FastenersFasteners (Chapter 9)Thread symbol represents thread on drawingThread note provides thread specificationsUnless otherwise specified, geometric tolerances apply to pitch diameter Applying Positional Tolerancing to FastenersA: Location tolerance applies to the cylindrical axis of the pitch diameterB: Location tolerance applies to the cylindrical axis of the major diameterC: Location tolerance applies to the cylindrical axis of the minor diameter

A Projected Tolerance Zone Applied to a PrintLength is distance fastener extends into the mating part, thickness of the part, or height of a press-fit studPerpendicularity tolerance provides a tighter control than allowed by a positional toleranceA Projected Tolerance Zone Applied to a Print

Projected Tolerance Zone Representation First Option

Projected Tolerance Zone Representation Second Option

Virtual ConditionDetermined when designing mating partsViolating virtual condition risks the interchangeability of mating partsVirtual condition of a feature must be interchangeable with virtual condition of its mating partCalculating Virtual ConditionInternal Feature Formula:MMC SIZE OF THE FEATURE RELATED GEOMETRIC TOLERANCE = VIRTUAL CONDITIONExternal Feature Formula:MMC SIZE OF THE FEATURE + RELATED GEOMETRIC TOLERANCE = VIRTUAL CONDITIONZero Positional Tolerance at MMC with the Clearance Hole at Virtual Condition

Concentricity Geometric ToleranceEstablishes concentricitySpecifies a cylindrical tolerance zoneAxis of tolerance zone coincides with datum axisConcentricity Geometric ToleranceSpecifies that median points originating from feature surface must be within cylindrical concentricity tolerance zoneApplied only on an RFS basisRelated datum reference applied only on an RMB basisConcentricity Geometric Tolerance

Concentricity Geometric ToleranceForm irregularities of an actual feature can make it difficult to establish location of median pointsFinding median points requires analysis of surface variationsRunout or positional tolerancing used unless it is absolutely necessary to control median pointsSymmetry Geometric ToleranceApplied only on an RFS basisRelated datum reference applied only on an RMB basisPresents difficulty in inspecting median pointsPositional tolerance locating symmetrical features considered if symmetry is not requiredSymmetry Geometric Tolerance

Positional Tolerancing Locating Symmetrical FeaturesEstablishes a center plane-to-center plane controlUsed to locate one or more features symmetrically with respect to center plane of datum featurePositional Tolerancing Locating Symmetrical FeaturesDiameter symbol omitted in feature control framePositional tolerance zone is distance between two parallel planes equally divided on each side of true positionMaterial condition must accompany positional toleranceRFS assumed otherwiseZero Positional Tolerance at MMC for Symmetrical ObjectsUse to control symmetry relationship of features within their limits of sizeDatum feature usually specified on MMB basisPerfect symmetry occurs and a boundary of perfect form is established when positional controlled feature is at MMC and datum feature is at MMBOut-of-perfect symmetry only happens as produced size leaves MMC Profile Tolerances on PrintsProfile can be used to control form or combinations of size, form, and orientationBased on true profileMust be contained within size tolerance when used as a refinement of sizeAlways RFSEqually disposed bilateral unless otherwise specifiedProfile geometric tolerance zone is generally oriented to one or more datumsProfile of a Line ToleranceUsed when it is unnecessary to control profile of the entire featureUsed when parts have changing cross sections throughout lengthAssumed to be equally disposed bilateral when leader from feature control frame extends to related surface without any additional clarificationProfile of a Line between Two PointsBetween symbol appears under feature control frameAny combination of letters usedTrue profile established with a basic or tolerance dimensionEqually disposed bilateral unless otherwise specifiedFeature confined within profile tolerance zoneProfile of a Line between Two Points

Profile of a Line All Around

Unilateral Profile of a LineUnequally disposed symbol appears after geometric tolerance in feature control frameTolerance value repeated after unequally disposed symbol when the tolerance has material added to feature or partUnilateral Profile of a Line

Unilateral Profile of a LineTolerance value placed before the unequally disposed symbol when the tolerance has material taken from the feature or part0 appears after the unequally disposed symbolSpecifies entire profile tolerance is inside of true profileAlternate Unilateral Profile Tolerance OptionShort phantom line appears parallel to the true profile on the side of the intended unilateral toleranceDimension line with an arrowhead placed on the far side and a leader line connected to the feature control frame with a leader line on the other sideUnequally Disposed Profile of a LineTotal profile tolerance value appears before the unequally disposed symbol in feature control frameValue of tolerance that adds material to the feature or part placed after the unequally disposed symbolUnequally Disposed Profile of a Line

Alternate Unequally Disposed Profile Tolerance OptionEither inside or outside of true profile shown as a basic dimensionDimension line with arrowheads placed on each side of the phantom lines and connected to the feature control frame with a leaderActual profile of part must be between the basic zone created around the true profileProfile of a Surface ToleranceUse to control entire surface as a single featureExtends along total length and width or circumference of object or feature(s)Establishes a blanket toleranceEqually disposed bilateral unless otherwise specifiedNormally requires reference to datums for proper orientation of profileProfile of a Surface Between Two Points

Profile of a Surface All Around or All OverEstablishes a blanket toleranceSurfaces all around or all over object outline must lie between two parallel boundaries equal in width to given geometric toleranceTolerance zone should be perpendicular to datum planeProfile of a Sharp CornerTolerance zone extends to intersection of the boundary linesA rounded corner can occurControlled using a maximum radius noteUnilateral or Unequally Disposed Profile of a Surface

Coplanar Profile ToleranceUsed to control profile of coplanar surfaces as a single surfacePhantom line appears between surfaces in the view where required surfaces appear as linesLeader connects from feature control frame to phantom line and a note appears below feature control frame identifying the number of surfacesCoplanar Profile Tolerance

Profile of Plane SurfacesUsed to control form and orientation of planar surfacesCan be used to control the angle of an inclined surface in relationship to a datumSurface must lie between two parallel planes equally split on each side of a true plane that has a basic angular orientation to a datumProfile of Conical FeaturesControls form or form and orientationControls feature independently as a refinement of size or orients feature to a datum axisProfile tolerance must be within the size toleranceActual surface must lie between two coaxial boundaries equal in width to the specified geometric tolerance, having a basic included angle, and within the size limitsComposite Profile ToleranceFeature control frame doubled in heightGeometric characteristic symbol placed in first compartment Locating tolerance zone specified in top half of feature control frameDatum reference given in order of precedence in feature control frameFeature to be controlled from datums located with basic dimensionsComposite Profile ToleranceProfile form and orientation tolerance zone specified in bottom half of feature control frameDatum referencing establishes limits of size, form, and orientation of profile related to locating tolerance zoneActual feature surface must be within both tolerance zonesProfile of a Feature to Be RestrainedIdentify datum featuresProvide a note specifying process used and force required to restrain the partRunout Geometric ToleranceUsed to control surfaces constructed around or perpendicular to a datum axisControl of circular elements of a surfaceControl of cumulative variations of circularity, straightness, coaxiality, angularity, taper, and profile of a surfaceControl of variations in perpendicularity and flatnessRunout Geometric ToleranceAlways specified RFSDatum references always specified RMBFeature control frame connects to surface by a leader lineMultiple leaders used to direct a feature control frame to two or more surfaces having a common runout toleranceCircular RunoutControls circularity and coaxiality when applied to surfaces constructed around or perpendicular to a datum axisCan be used to control wobbling motionControlling datum verified before checking other surfacesReference datum always RMBCircular RunoutMeasured by full indicator movement (FIM) of a dial indicator placed at several circular measuring positions as part is rotated 360FIM is a total toleranceEach circular element must lie within the FIMDatum axis for runout inspection estabished using a clamping deviceCollet typicalCircular Runout

Total RunoutControls combined variations of circularity, straightness, coaxiality, angularity, taper, and profile when applied to surfaces constructed around and at right angles to a datum axisCan control combined variations of perpendicularityCan control concavity or convexity when applied to surfaces perpendicular to a datum axisTotal RunoutReference datums always RMBTolerance zone encompasses entire surface as part is rotated 360Entire surface must lie within specified tolerance zoneDial indicator is placed at every location along surface as part is rotated 360Total Runout

Runout Applied to a Portion of a Surface and Two Datum ReferencesChain line located with basic dimensions appears in linear viewFeature control frame connects to chain line by a leaderDatum identifying letters placed in feature control frameLetters separated by a dashRunout Applied to a Datum Surface and a Datum AxisDatums placed separately in feature control frame in order of precedenceProfile must be within specified geometric tolerance when part is mounted on the datum surface and rotated 360 about the datum axisDatum reference always specified RMBRunout Control Applied to a DatumDatum feature symbol specified to apply runoutDatum feature symbol centered below feature control frame or datum feature symbol connected to the leader shoulderCombining Runout with Other Geometric TolerancesUsed in runout tolerancing applicationsProfile and circular runoutRunout and cylindricity Specify IndependencyForm control is independent of size tolerance and should be added to the featureSize is verified by a two-point check using a micrometer or caliperForm is checked using the runout toleranceGlossaryAcceptance boundaryThe maximum size plus the allowable out-of-straightness tolerance.Actual mating envelopeThe smallest size that can be contracted about an external feature or the largest size that can be expanded within an internal feature.Actual produced sizeThe measured size after production.GlossaryAngularityThe condition of a surface, center plane, or axis at any specified angle from a datum plane or axis.Angularity toleranceA tolerance established by two parallel planes or cylindrical zones at any specified basic angle, other than 90, to a datum plane, a pair of datum planes, or an axis.Average diameterThe average of several measurements across a circular or cylindrical feature.GlossaryAxis geometric controlThe control (using a geometric tolerance) of an axis of a feature or object. The feature control frame is placed with the diameter dimension of the related object or feature.Axis straightnessA tolerance specified by placing the feature control frame below the diameter dimension and placing a diameter symbol in front of the geometric tolerance to specify a cylindrical tolerance zone.Basic dimensionA theoretically perfect dimension. Basic dimensions are used to describe the theoretically exact size, profile, orientation, or location of a feature or datum target.GlossaryCircular runoutA type of runout that provides control of single circular elements of a surface.CircularityA form tolerance that is characterized by any given cross section taken perpendicular to the axis of a cylinder or cone, or through the common center of a sphere.Circularity toleranceA tolerance formed by a radius zone creating two concentric circles within which the actual surface must lie.GlossaryCoaxial featuresFeatures having a common axis, such as counterbores, countersinks, and counterdrills.Coaxial positional toleranceA tolerance used to control the alignment of two or more holes that share a common axis.ColletA cone-shaped chuck used for holding cylindrical pieces in a lathe or inspection machine.GlossaryComposite positional tolerancingA tolerancing method used when it is desirable to permit the location of a pattern of features to vary within a larger tolerance than the positional tolerance specified for each feature.Composite profile toleranceA tolerance that provides for the location of a profiled feature and, at the same time, the control of form and orientation.Concentricity geometric toleranceA tolerance used to establish a relationship between the axes of two or more cylindrical features of an object.GlossaryCylindricityA form tolerance identified by a radius tolerance zone establishing two perfectly concentric cylinders within which the actual surface must lie.Datum axisThe center axis established when a cylindrical datum feature is used.GlossaryFlatnessA condition where all elements of a surface are in a single plane.Flatness toleranceA tolerance that establishes the distance between two parallel planes within which the surface must lie.Flatness tolerance zoneA tolerance zone that establishes the distance between two parallel planes within which the surface must lie.GlossaryOrientation geometric tolerancesTolerances that control the relationship of features to one another. When controlling orientation tolerances, the feature is related to one or more datum features.Parallelism geometric toleranceA tolerance established by two parallel planes or cylindrical zones that are parallel to a datum plane, and between which the surface or axis of the feature must lie.ParallelismThe condition of a surface or center plane equidistant from a datum plane or axis.GlossaryProfileThe outline of an object represented either by an external view or a cross section through the object.Profile toleranceA tolerance that specifies a uniform boundary along the true profile within which the elements of the surface must lie.Projected tolerance zoneA tolerance zone that is established at true position and extends away from the primary datum. A projected tolerance zone is recommended when variations in perpendicularity of threaded or press-fit holes could cause the fastener to interfere with the mating part.GlossaryRadial elementA line element on the contour of a radial surface.Rectangular coordinate dimensioningThe use of linear dimensions to locate features from planes, centerlines, or center planes.Regardless of feature size (RFS)The term used to indicate that a geometric tolerance applies at any increment of size of the feature within its size tolerance. RFS is assumed for all geometric tolerances unless otherwise specified.GlossaryUnit flatnessA specification used when it is desirable to control the flatness of a given surface area as a means of controlling an abrupt surface variation.Virtual conditionA boundary that takes into consideration the combined effect of feature size at MMC and geometric tolerance.