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Chapter Seven

Orientation Controls

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Interpret the perpendicularity control

Interpret the angularity control

Interpret the parallelism control

Chapter Goals

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We are going to explore controls that apply tothe orientation of a part.

These controls are for the perpendicularity,

angularity and parallelism of the part.

Orientation controls are used when otherdrawing limits are inadequate to control the

assembly or fit for function of a part.

Introduction

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Implied right angles Two lines shown at 90 degrees create an implied

90 degree angle with a tolerance usually noted in

the title block or a note on the drawing. Shortcomings of implied 90 degree angles

Tolerance zone is fan shaped that is gets biggerthe farther you are from the origin of

measurement. No datum to inspect from? What side is the

inspection done from?

Perpendicularity Control

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Coordinate Tolerancing and

Perpendicularity

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The condition that results when a surface, axisor centerplane is exactly 90 degrees to adatum.

Perpendicularity Control

A geometric tolerance that limits the amount a

surface, axis or centerplane is permitted to vary

from being perpendicular to the datum.

Perpendicularity

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Two Parallel PlanesA Cylinder 

Perpendicularity Tolerance Zones

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Applied to a surface

Shape of the zone is two parallel planes

perpendicular to the datum plane.

Tolerance value of the perpendicularity controldefines the distance separating the two planes.

All elements of the surface must be within the

tolerance zone. The perpendicular tolerance zone limits the

flatness of the tolerance surface.

Perpendicularity Applications

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Add Picture of Perp to a surface

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Applied to a planar FOS Used to ensure assembly.

Certain Rules Apply Tolerance zone is two parallel planes perpendicular to

the datum plane. Tolerance value of the perpendicularity control

defines the distance separating the two planes. Centerplane of the AME of the FOS must be within

the tolerance zone. Bonus tolerance applies Fixed gage may be used to verify perpendicularity

control.

Perpendicularity Applications

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Perpendicular Control to a planar

Surface

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Applied to a cylindrical FOS Controls the axis of the FOS.

Tolerance zone is a cylinder perpendicular to thedatum plane

Tolerance value of the perpendicularity controldefines the diameter of the tolerance zone cylinder.

Axis of the diameter must be within the tolerancezone (when FOS is at MMC).

Bonus tolerance allowed.

WCB of the diameter is affected.

Fixed gage may be used to verify.

Perpendicularity Applications

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Perpendicular Control on a Cylindrical

FOS

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A perpendicular control applied to a surfacedoes not affect the WCB but a perpendicularcontrol applied to a FOS does.

Note that the WCB of a FOS that istoleranced with an orientation is orientedrelative to the datum's specified.

More Perpendicular Control Notes

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Several controls indirectly affectperpendicularity.

Tolerance of position

Runout

Profile

Indirect controls are not measured. If you

want perpendicularity inspected, apply thecontrol.

Indirect Perpendicular Controls

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Review flow chart pg. 185 fig. 7-7.

Note that this applies only to RFS datumreferences only.

Note that if the control is applied to a surfacethen the projected tolerance zone, diameter,MMC and LMC may not be used in thetolerance portion of the feature control frame.

Legal Specification

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There are three separate checks needed toverify the control.

Size of FOS

Rule One Boundary

Perpendicularity requirement

The inspection of the perpendicularity

requirement is a reverse go gage.

Inspecting Perpendicularity

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Insert Inspection Picture

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The condition of a surface, centerplane or axisbeing exactly at a specified angle.

The control is a geometric tolerance thatlimits the amount a surface or centerplane isallowed to vary from its specified angle.

Angularity Control

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Two Parallel Planes Cylinder  

Need Pictures

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WCB of the toleranced surface is not affected. Tolerance zone is two parallel planes Angularity control tolerance defines distance

between zone planes All elements of surface must lie between zone

planes Tolerance zone is oriented relative to the datum

plane by a basic angle Angularity tolerance zone limits flatness of

toleranced surface

Angularity Applied to a Surface

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Angularity Applied to a Surface

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The WCB of the FOS is affected.

If FOS is toleranced with an orientationcontrol, the WCB is oriented relative to the

datums specified.

If an angularity control is applied to acylindrical FOS, some new rules apply.

Angularity Applied to a Cylindrical FOS

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Tolerance zone is a cylinder. Angularity control tolerance defines diameter

of tolerance cylinder.

Axis of toleranced feature must be withintolerance zone.

Tolerance zone is oriented relative to the

datum plane by a basic angle. An implied 90 degree basic angle exist in the

other direction.

Angularity Applied to a Cylindrical FOS

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Angularity Control to a Diametrical FOS

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Note thetwo

datums

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Several geometric controls indirectly affectangularity of a part feature. Tolerance of position Total runout

Profile Remember that indirect controls are not

inspected. If you need the angularity checked, usean angularity control.

Also note that the tolerance of angularity controlshould be less than the tolerance value of anyindirect control.

Indirect Angularity Controls

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Review Flow sheet page 190, fig. 7-11.

Legal Test of an Angularity Control

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Verifying Angularity

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Implied Parallelism

If two surfaces are shown parallel on a drawing,

the size dimensions of the surfaces controls the

parallelism between the surfaces. Poor inspection due to lack of datums and

parallelism has same dimensions as size.

Not a good way to design.

Parallelism Control

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Implied Parallelism Picture

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Parallelism is the condition that results when asurface, axis or centerplane is exactly parallelto a datum.

The control is a geometric tolerance thatlimits the amount a surface, axis orcenterplane is permitted to vary from being

parallel to the datum.

Parallelism Control

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Two Parallel Planes Cylinder/Diameter  

Parallelism Tolerance Zones

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If a parallelism control is applied to a surface, thefollowing applies: Tolerance zone is two parallel planes parallel to the

datum plane.

Tolerance zone is located within the limits of the sizedimension. Tolerance value of the parallelism control defines the

distance between tolerance zone planes. All elements of the surface lie within the tolerance

zone. Parallelism tolerance zone limits flatness of the

toleranced feature.

Parallelism Applications

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If parallelism control, containing the MMCmodifier, is applied to a cylindrical FOS, thefollowing applies: Tolerance zone is a cylinder parallel to the datum

plane. Tolerance value of the parallelism control defines the

diameter of the tolerance zone cylinder. Axis of the cylinder must be within tolerance zone,

when FOS is at MMC. Bonus tolerance is permissible. Fixed gage may be used. WCB or VC of the hole is affected.

Parallelism Applications

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35

When a surface is to be parallel to a datum, thefeature control frame is either connected by aleader to the surface or directly connected to the

extension line of the dimension.

Parallelism Applied to a Surface

Parallelism to a Surface

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When parallelism is applied to an axis the axis ofthe hole may be specified within a tolerance zonethat is parallel to a given datum.

The feature control frame is place with the diameterdimension

Parallelism Applied to an Axis

Parallelism to a FOS

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Tangent plane modifier, , denotes that onlythe tangent plane established by the highpoints of the controlled surfaces must be

within the parallelism tolerance zone. If the tangent plane modifier is used, the

flatness of the tolerance surface is not

controlled.

Parallelism with Tangent Plane Modifier

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T

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Other rules apply: Tolerance zone is two parallel planes.

Tangent plane is established by the high points of

the surface and must be within the tolerance zoneof the control but is not a flatness control.

Tolerance zone will “float”.

Parallelism with Tangent Plane Modifier

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Tangent Plane Modifier Application

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Several geometric controls indirectly affectparallelism of a feature.:

Tolerance of position

Total runout

Profile

Remember that indirect controls are not

measured. To measure parallelism one mustuse a control.

Indirect Parallelism Controls

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Review fig. 7-17, page 197.

Legal Specification Test for Parallelism

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Inspecting Parallelism

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Summary Table

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Questions?

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Chapter Eight

Tolerance of Position, Part One

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Understand fundamental concepts oftolerance of position; definitions, conventions,advantages and basic theories.

Interpret RFS and MMC tolerance of positionapplications.

Draw cartoon gages for tolerance of position

(MMC) applications.

Chapter Goals

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True position: the theoretically exact locationof a FOS as defined by basic dimensions.

Tolerance of Position Control: a geometrictolerance that defines the location toleranceof a FOS from its true position.

Definitions and Conventions

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A TOP control, specified at RFS, defines atolerance zone that the center, axis, orcenterplane of the AME of a FOS must be

within. If specified on an MMC or LMC basis, TOP

control defines a boundary, VC, that may not

be violated by the surface(s) of theconsidered feature.

Definitions and Conventions

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If specified at RFS, the TOP feature controlframe will have no modifiers. Remember thatRFS is the default condition for all geometric

tolerances.

Definitions and Conventions

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TOP Feature Control Frames

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When a TOP control is specified, thetheoretically exact location of the axis orcenterplane of the FOS must be defined with

basic dimensions. This exact location is called the true position

of the FOS.

Definitions and Conventions

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TOP Tolerance Zone and True Position

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Basic dimensions define the true position relativeto the referenced datums.

If basic dimensions are not specified, they areimplied. Implied basic 90 degree angle: applies where

centerlines of features are located and defined bybasic dimensions and no angle is specified.

Implied basic zero dimension: a centerline orcenterplane of a FOS is shown in line with a datumaxis or centerplane, the distance between thecenterlines or centerplanes is an implied basic zero.

Definitions and Conventions

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I li d A l d Z Di i

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Implied Angles and Zero Dimensions

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Provides larger tolerance zones; cylindricaltolerance zones are 56% larger than squarezones.

Permits bonus tolerance and datum shift. Prevents tolerance accumulation.

Permits use of functional gages.

Protects part function.

Lowers manufacturing costs.

Advantages of Tolerance of Position

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Commonly used with TOP controls.

57% larger tolerance zone?

How?

Bonus and Datum shift add additionaltolerance, up to 100%.

Help clarify drawing to manufacturing

Reduces overall cost.

Cylindrical Tolerance Zones

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CT d TOP T l Z C i

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CT and TOP Tolerance Zone Comparison

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Distance between features of size such asholes, bosses, slots, tabs, etc.

Location of features of size, or patterns of

features of size, such as holes, bosses, slots,tabs, etc.

Coaxiality between features of size.

Symmetrical relationship between features ofsize.

What Can Be Controlled With TOP?

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If TOP controls are used, you must specify underwhich material condition the control is to apply.(MMC, LMC or RFS).

The function of the FOS being toleranced is theprimary dictate for the material condition.

Cost of production is a secondary considerationbut still important.

Do not forget inspection cost. Note that the MMC modifier is most common

and least costly.

Tolerance Of Position Modifier Usage

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Guide For Selecting TOP Control

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Guide For Selecting TOP Control

Modifiers

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Virtual Condition Boundary Theory: Theoretical boundary that limits the location of

the surfaces of a FOS.

Axis Theory: Axis or centerplane of a FOS must be within the

tolerance zone.

Tolerance of Position Theories

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TOP at MMC Hole must be specified limit of size.

Located so no element of its surface will be inside

a theoretical boundary. Theoretical boundary centered about true

position of the hole.

Theoretical boundary is equal to the MMC of the

FOS minus the TOP tolerance.

Theoretical boundary is the VC of the hole (gage pin).

Virtual Condition Boundary Theory

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TOP VCB for Internal FOS

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A TOP is also an indirect orientation control.

The theoretical boundary is orientatedrelative to the primary datum referenced in

the TOP callout. The gage pin also limits the orientation of the

FOS.

Virtual Condition Boundary Theory

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Virtual condition boundary theory also appliesto an external FOS.

Theoretical boundary for a TOP, at MMC, of an

external FOS is the MMC of the FOS plus theTOP tolerance.

Location and orientation of the FOS is limited by

the TOP control.

TOP VCB for External FOS

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TOP VCB Th f E l FOS

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TOP VCB Theory for External FOS

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A Th

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Used when TOP is applied at RFS. Specified TOP applies at whatever size the FOS is

produced at.

Axis of the hole AME must be within the TOPtolerance zone cylinder.

The TOP tolerance zone cylinder is centeredaround the true position of the hole.

The diameter of the TOP tolerance zone is equalto the tolerance value specified in the TOPcallout.

Axis Theory

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TOP A Th I l FOS

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TOP Axis Theory: Internal FOS

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A i Th

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A TOP is also an indirect orientation control. The theoretical boundary is orientated

relative to the primary datum referenced in

the TOP callout. Tolerance zone that controls the location of

the FOS also limits the orientation of the FOS.

Axis Theory

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TOP A i Th I l FOS

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TOP Axis Theory: Internal FOS

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A i Th Pl F f Si

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Tolerance zone for a TOP, applied at RFS, of anexternal planar feature of size is two parallelplanes spaced apart at a distance equal to the

TOP tolerance. The orientation and location of the

centerplane of the AME of the FOS is limited

by the TOP tolerance zone.

Axis Theory: Planar Features of Size

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TOP A i Th E l Pl FOS

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TOP Axis Theory: External Planar FOS

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C TOP RFS A li i

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Three conditions are present when a TOPcontrol is applied at RFS:

Tolerance zone applies to the axis or centerplane

of the FOS. Tolerance value applies regardless of size of the

toleranced FOS.

Requirement must be verified with a variable gage.

Review Chart on page. 216.

Common TOP RFS Applications

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RFS T l Z

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In TOP, when it is an RFS situation, there aretwo tolerance zones commonly found:

Fixed diameter cylinder

Two parallel planes a fixed distance apart The diameter of the cylinder or the distance

between planes is equal to the tolerance value

specified in the TOP callout. Location of the tolerance zone is always

centered around the true position of the FOS

RFS Tolerance Zones

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RFS T l Z Sh

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Figure 8-9, page 219 has a diameter symbol inthe tolerance portion of the FCF. This says acylindrical tolerance zone.

Figure 8-10, page 220, there is no diametermodifier in the tolerance portion of the FCF.

This says the tolerance zone is two parallelplanes.

RFS Tolerance Zone Shapes

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H l L ti C t ll d b TOP t RFS

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Hole location may be controlled with a TOP atRFS. Figure 8-11 shows such a situation. Theaxis of the hole is controlled relative to the

outside surfaces of the part.

Hole Location Controlled by TOP at RFS

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H l L ti C t ll d b TOP t RFS

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Following rules apply here: Shape of tolerance zone is a cylinder

Tolerance zone is located by basic dimensions relativeto the datum planes

Tolerance zone is RFS Dimension between centerline of hole and datum A is

an implied 90 degrees

No datum shift is possible

Tolerance zone controls orientation of hole relativeto the primary datum from TOP callout

WCB of hole is affected..6.0-0.2=5.8

Hole Location Controlled by TOP at RFS

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H l C t ll d With TOPS @ RFS

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Hole Controlled With TOPS @ RFS

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P tt f H l L t d b TOP @ RFS

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When more than one hole, a pattern, is located by aTOP at RFS, certain conditions will apply. An example isfig. 8-12, pg. 225.

The following applies: Shape of tolerance zone is cylindrical Tolerance zone is located by basic dimensions Tolerance zones are at RFS Tolerance zones control orientation of holes relative to

the primary datum

Tolerance zones are at an implied 90 basic degrees todatum A Rule One applies

Pattern of Holes Located by TOP @ RFS

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Coaxial Diameter Position

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When the location of coaxial diameters iscontrolled by a TOP @ RFS, the following applies: Tolerance zone is a cylinder

Tolerance zone is applied at RFS

Dimension specifying the location of the diameterrelative to the datum feature is an implied zero

Tolerance zone limits the orientation of thetoleranced diameter relative to the datum A axis

No datum shift allowed

Rule one applies

Coaxial Diameter Position

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Coaxial Diameters Controlled by TOPs @ RFS

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Coaxial Diameters Controlled by TOPs @ RFS

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Inspecting TOP Applied At RFS

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Three separate checks are needed to verifypart:

Size of hole

Rule one boundary TOP requirements

Hole size and rule one was explained before.

TOPS inspecting requires a variable gage. Coordinate Measurement Machine is the ideal

Inspecting TOP Applied At RFS

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Common TOP MMC Applications

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A TOP applied at a max material condition isspecified when function, assembly or theeffects of a bonus tolerance/datum shift wouldnot affect the actual function/assembly of thepart.

If a TOP @ MMC is used, the following applies: Tolerance zone is considered a boundary zone

Bonus tolerance and datum shift is allowed Requirement can be verified with a functional gage

Common TOP MMC Applications

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MMC and RFS Comparison

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MMC and RFS Comparison

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Hole Location Controlled with TOP @ MMC

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@

Hole Pattern Controlled By TOP @ MMC

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If a hole pattern is controlled by TOP @ MMC, thelocation of the holes is controlled relative to the partedges and the following applies: Tolerance zone shapes are Virtual Condition boundaries

Tolerance zones are located by basic dimensions from thedatum planes

Relationship between centerlines of holes and datum planeA is implied basic 90 deg.

Bonus tolerance is permissible

Rule one applies

Tolerance zone controls orientation of the holes relativeto the primary datum referenced in TOP callout

Hole Pattern Controlled By TOP @ MMC

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Coaxial Diameter Applications

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90

Coaxial Diameter Applications

Legal Specification Test For TOP

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For a TOP to be a legal callout, the followingapplies: TOP must be applied to a FOS

Datum references are required

Basic dimensions must be used to establish the trueposition of the toleranced FOS from the datumsreferenced and between FOS in a pattern

All of these conditions must be met or callout is

not legal. Refer to fig.8-19, pg.234

Legal Specification Test For TOP

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Inspecting TOP at MMC

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Multiple types of gages may be used to verify aTOP applied at MMC. These include: CMM

Variable gages

Other functional gages

A functional gage is one that verifies functionalrequirements of part features as defined by the

geometric tolerances. This means that a functional gage mimics the actual

function of the part being measured.

Inspecting TOP at MMC

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Benefits of a Functional Gage

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Represents worst case mating part Parts may be verified quickly

Economical to produce

No special skills needed to read or interpretresults

Functional gage may be able to check several

part characteristics at the same time

Benefits of a Functional Gage

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Reality of a Functional Gage

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Gage should represent the virtual conditionofthe toleranced FOS

Note that the TOP applied at MMC may be

verified by other devices, such as an CMM.Note that a functional gage must also be

verified as to dimensional correctness

Reality of a Functional Gage

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Cartoon Gage

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A sketch of a functional gage. A cartoon gagedefines the same part limits that a functionalgage would, but it does not represent the

actual gage construction of a functional gage. A cartoon gage construction is described in

figure 8-20, page 237.

Cartoon Gage

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More Cartoon Gages

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More Cartoon Gages

97

The cartoon gage for this

application was drawn using the

designer’s judgment. The effects

of the TOP callout are added to

the MMC of the toleranced

diameter to produce the virtual

condition. The gage must also

be built to conform to the virtual

condition of datum B.

Note that the gage only checksorientation and location. Form

and size must be checked

separately.

Summary of TOP Information

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Review figure 8-22, page 239.

Summary of TOP Information

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Questions?

99

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Geometric Dimensioning and

Tolerancing

CAD 2204

Spring 2010

100

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Chapter Nine

Tolerance of Position: Part Two

101

Chapter Goals

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Interpret tolerance of position specialapplications.

Calculate distances on a part dimensioned

with tolerance of position. Calculate tolerance of position tolerance

values using the fixed and floating fastener

formulas.

Chapter Goals

102

TOP Locating Non-Parallel Holes

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There are times that holes are not parallel orperpendicular to the datum axis. In order tocontrol the location and orientation of these

holes, a TOP control is used.

Figure 9-1 is one example.

TOP Locating Non Parallel Holes

103

TOP Locating Non-Parallel Holes

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There are some rules or conditions that applyin this type of instance: Tolerance zone is the cylindrical virtual condition

boundary. What is the VC? VC=MMC – Geo. Tol.

Tolerance zones are located by basic dimensionsrelative to the referenced datums.

Angle of the hole, relative to datum B, is limited bythe TOP.

Bonus tolerances are permitted.

TOP Locating Non Parallel Holes

104

TOP Applied To Non-Parallel Holes

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TOP Applied To Non Parallel Holes

105

Bi-Directional TOP

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There are times we need to provide a hole atolerance in more than one direction. This iswhere a bi-directional control is used.

Two feature control frames are used and eachone is attached to a dimension line of the holein the direction you need controlled.

Figure 9-2 is an example of this instance.

Bi Directional TOP

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Bi-Directional TOP

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The following applies to this bi-directionalTOP application:

Tolerance zones are parallel boundaries in the

direction of the TOP control. Shape of the tolerance zones is irregular.

Tolerance zones are located by basic dimensions

relative to the datums referenced.

Bonus tolerances are permitted.

Bi Directional TOP

107

Bi-Directional TOP

What is

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Bi Directional TOP

108

the VCformula?

Elongated Holes

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Elongated holes are unique in the application ofTOP. One would think that this type of holeneeds to have bi-directional TOP controls. In factthis is the best way of design but you could stilluse one TOP.

Again the feature control frames are attached tothe dimension lines and the word BOUNDARY is

added beneath each feature control frame. Figure 9-3 is an example of this application.

Elongated Holes

109

Elongated Holes

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The following conditions apply for thisapplication: Tolerance zone is a boundary of the identical

shape as the elongated hole, minus the position

tolerance value in each direction. Why?

Tolerance zones are located by basic dimensionsrelative to the datums referenced.

Bonus tolerances are permitted.

Elongated hole must meet size requirements.

o gate o es

110

Elongated Hole Application

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g pp

111

Whathappens ifonly one

TOPcontrol is

used?

TOP and Projected Tolerance Zone

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Threaded hole dimensioning is not easy. Onemust consider just what is being dimensionedand how the rest of the design is affected.

Figure 9-4 is an example of this issue.

j

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113

TOP and Projected Tolerance Zone

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The squareness error of the pin or fastenerhas resulted in an interference fit with thehole. This prevents proper torque being

applied or fastener being fully seated. To eliminate this condition, one should use a

projected tolerance zone.

Back to Figure 9-4.

j

114

TOP and Projected Tolerance Zone

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j

115

PTZ

Projected Tolerance Zone

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A tolerance zone that is projected above the partsurface. There is a specific symbol for a PTZ,, this would be placed in the tolerance section ofthe feature control frame.

Several conditions apply to a PTZ:

Height is specified after the symbol in the FCF.

Should be equal to the thickness of the mating part.

Orientation of the fastener is fixed.

Figure 9-5 is another example.

j

116

P

TOP & PTZ Example

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117

TOP & Symmetrical Relationships

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If symmetry is critical relationship on a part, thecenterplane of the part (AME) may be controlledwith a TOP control.

Figure 9-6 is an example of this application.

These conditions would apply: Tolerance zone shape is two parallel plates.

Tolerance zone is located by implied basic zerodimensions.

Bonus tolerance is allowed.

Datum shift is allowed.

y p

118

Symmetry Controlled With TOP

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y y

119

Can also beused at LMC

and RFS

TOP With MMC Modifier

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If one needs to control a minimum distance on apart, say a wall thickness, then a TOP control withan LMC modifier will work.

Figure 9-7 is an example of this application.

Some conditions apply: Tolerance zone shape is a cylindrical boundary.

Dimension between centerline of diameter and datumaxis is an implied zero.

Bonus tolerance is allowed.

Perfect form at LMC applies.

120

TOP @ LMC

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@

121

MW= 1.6 [(24.2-20.8-.2)/2=1.6]

TOP with Pattern of Holes

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If one wants to only control the spacing andorientation of holes in a pattern, a TOPcontrol with a single datum may be used.

In figure 9-8, we have an example of a TOPcontrol limiting the spacing between holes andthe orientation about datum A but there is nocontrol over location.

Further, the gage only checks perpendicularityand spacing.

122

TOP & Hole Pattern

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123

Multiple Single-Segment TOP Controls

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Sometimes you may want to control location,spacing and orientation of a pattern offeatures of size. Then multiple single segment

TOP controls will be used. Figure 9-9 is an example of this application.

Note that the upper segment tolerances

location while the lower tolerances spacingand orientation.

124

Multiple TOP Segments

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125

TOP @ Zero Tolerance at MMC

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Zero tolerancing is a method of helpingmanufacturing produce a quality part with thelowest cost.

ZT @ MMC simply states a zero tolerance atMMC but places the geometric tolerance withthe FOS tolerance.

Figure 9-10 illustrates this application.

126

ZT @ MMC

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127

A Tolerance Analysis Chart

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128

TOP Calculations

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Tolerance stacks at RFS This method will allow you to calculate the

minimum and maximum distance between the

edges of two holes.

The process uses the basic dimensions between

holes, TOP tolerance value and the MMC or LMC

hole size.

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Tolerance Stacks @ MMC

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Here we are going to use something called thegage method. This method involves using acartoon gage to calculate distance.

An advantage is that bonus tolerances anddatum shifts are automatically included in thecalculations.

The five steps are illustrated in figure 9-13.

131

Tolerance Stack:TOP @ MMC

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132

TOP @ MMC

Five steps:1. Draw the cartoon gage.

2. Draw the part on the gage in

the position that gives the

extreme condition being

calculated.

3. Label start and end points ofthe distance calculated.

4. Establish a path of

continuous known distances

from the start point to the

end point.

5. Calculate the answer.

AnotherExample

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133

Example

Fixed Fastener Assemblies

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This is where the fastener is fixed orrestrained by/into one of the components ofthe assembly.

Typically a screw, stud or other threaded fastener. Figure 9-15 is an example of screws as fixed

fasteners.

134

Fixed Fastener

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135

Fixed Fastener Formula

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This formula determines the amount oftolerance for a fixed fastener and needs tohave the projected tolerance modifier used onthe threaded hole.

The formula is: T = (H – F)/2

T is position tolerance diameter

H is MMC of the clearance hole F is MMC of the fastener

136

Fixed fastener Example

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137

Fixed Fastener Notes

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In figure 9-16, the MMC modifier is used asthe function of the holes is assembly. TheMMC allows for additional tolerance for

assembly.Now the projected tolerance zone may not be

specified, if that happens the tolerance formulachanges to :

T = F + 2T

Symbols still mean the same.

138

Floating Fastener Assemblies

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A floating assembly is where the componentsare held together by a combination of a boltand nut or some other type of fastener where

both of the fastened components haveclearance holes for the fastener.

Figure 9-17 is an example of such anapplication.

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Floating Fastener Formula

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The formula for floating fasteners tolerance is: T = H – F

T is position tolerance

H is MMC of clearance hole

F is MMC of fastener

The tolerance when determined applies toeach part in the assemble.

The MMC modifier is needed. Figure 9-18 is an example of this application.

141

Floating Fastener Example

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Floating Fastener Notes

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Floating fasteners seem to be simple. Drill holes,keep tolerances adequate and check the formula.But there are other items to consider:

Clearance of the threaded portion where the nut

goes. Is the clearance for the threaded end?

Can you get the wrench or socket on the flat end? Isthere vertical and horizontal clearance?

When the assembly is put into the system, will therebe room for service or is this a blind assembly?

143

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Questions?

144

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Chapter Ten

Concentricity and Symmetry Controls

145

Chapter Goals

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Interpret the concentricity control

Interpret the symmetry control

146

Concentricity Control

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Concentricity is a condition where the medianpoints of all diametrically opposed elements ofa cylinder or surface of revolution arecongruent with the axis of a datum feature.

Note: Median points are at the midpoint of a

two point measurement.

147

Concentricity Tolerance Zone

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148

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Concentricity Examples

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150

Concentricity Notes

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All of the coaxiality controls are intended to controlconcentric features. For that reason, many designers andengineers choose concentricity. Unfortunately, concentricityignores the size, roundness and cylindricity of the feature. Itrequires that the inspector derive a median line. In asituation where you don't care about the size, roundness or

cylindricity of the feature, concentricity may be specified. Ido know of a design where this is truly the case. Theclosest application, perhaps, is when dynamic balance isneeded. In such a case, measuring a part statically does notassure dynamic balance if the material is not homogeneous.

If dynamic balance is required, a dynamic balancing note isprobably in order rather than concentricity. For that reason,When in Doubt, Use Runout."

151

Concentricity example

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Concentricity Example

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153

Runout Review

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154

Concentricity Example

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But first some notes: Diameter must meet the size and rule 1 requirements.

Concentricity control tolerance zone is a cylinder thatis coaxial with a datum axis.

Tolerance value defines the diameter of the tolerancezone.

All median points of the toleranced diameter must bewithin the tolerance zone.

The maximum distance between median points is halfthe concentricity tolerance value.

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Concentricity Example

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156

Concentricity, Runout and TOP @ RFS

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157

More Notes

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158

More Notes

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Total runout is thedifference betweenthe highest andlowest readingsfound over theentire feature. Thehighest reading was+0.02 and thelowest reading was-0.09. Therefore,the total runoutfor the feature is0.11, the differencebetween +0.02 and-0.09.

159

Legal Specification Test ForConcentricity Control

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Page 286 has the flowchart for the test todetermine if a concentricity control specificationis legal. Note the conditions stated:

FCF must be applied to a surface of revolution coaxial

to the datum axis.

Datum references are required.

The concentricity symbol must be in the toleranceportion of the FCF.

MMC, LMC, Tangent Plane and Projected ToleranceZone may not be used in the FCF.

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Inspecting ConcentricityMust

calc late

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162

calculateand locate

the medianpoints.

Five Ways To Control Coaxiality ofFeatures

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GD&T Symbols

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164

Symmetry

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Symmetry is the condition where the medianpoints of all opposed elements of two ormore feature surfaces are congruent with theaxis or centerplane of a datum feature.

What this means is that opposed points mustbe equally spaced or apart and meet theconditions of the control.

165

Symmetry Control

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This is a geometric tolerance that limits thesymmetry error of a part feature.

This control only works when applied to part featuresshown symmetrical to the datum centerplane.

The tolerance zone is centered about the datumcenterplane and the width is equal to the tolerancevalue.

All median points must lie within the parallel planetolerance zone regardless of feature size.

Symmetry controls are always applied at RFS.

166

Symmetry Example

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167

Symmetry Example

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168

Symmetry Application

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A symmetry control is a special applicationthat requires work on the part of the designeror inspector to determine. Remember thatone must determine the datum plane and thenthe tolerance zone locations in order tomeasure symmetry.

169

Symmetry Application

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Often designers need to create symmetricallyshaped parts. Symmetrical parts are usually easierto assemble, look better and help maintainbalance in a design. Features shown symmetricalmust be controlled to avoid incomplete drawing

requirements (2.7.3 of ASME Y14.5M-1994).Symmetry is an option in these situations but it isdifficult to measure since it requires deriving thefeatures' median points to determine if they are

contained within the specified tolerance zonewhich is centered on the datum axis or datumcenter plane.

170

Symmetry Application

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Position may also be used to assure asymmetrical relationship. The advantages of usingPosition include the ability to modify thetolerance and datum reference at RFS (implied in

1994 Standard), MMC or LMC. In addition,verification is usually easier for Position than thatrequired for Symmetry since it is the center planeof the Actual Mating Envelope (simulated by the

inspection equipment) that must be within thetolerance zone.

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Positional Control of Symmetry

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172

Symmetry Application

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When a symmetrical control is specified, thepart in question usually needs to have aspecific attribute of a part controlled. Specificareas may include wall thickness, functionalappearance and other factors that includebalance and fit.

If a symmetry control is applied, the following

applies:

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Symmetry Application

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Controlled feature must meet size and ruleone requirements.

Tolerance zone is two parallel planes centered

about the datum centerplane. Tolerance value of the symmetry control

dictates distance between parallel planes.

All median points of the toleranced featuremust be within the tolerance zone.

174

Symmetry Example

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Symmetry and TOP @ RFS Differences

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176

Legal Test For a Symmetry Control

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Figure 10-10 on page 291 is the flowchart ofquestions one needs to ask to ensure that thecontrol you want to use is properly written.

Take note of the questions. This is the same flow

we have always seen and will see in the next few

chapters.

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Inspecting Symmetry

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178

Summary of Chapter

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179

Symmetry may

also becontrolled by

position

What doconcentricity and

symmetry indirectlycontrol?

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Questions?

180

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Chapter Eleven

Runout Controls

181

Chapter Goals

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Interpret the circular runout control

Interpret the total runout control

182

R l Th h f

Runout

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Runout is a composite control. That is the form,location and orientation of a part feature iscontrolled simultaneously.

Runout controls may also control coaxiality ofdiameters.

Runout must always be applied with a datumreference.

Runout may be applied to any feature thatsurrounds or intersects a datum axis.

Runout is measured as the max indicator readingon the feature when rotated 360 degrees.

183

Circular runout

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First we must establish a datum axis.We do so by:

Using a single diameter

Two coaxial diameters sufficiently apart A surface and a diameter at right angles

Figure 11-2 illustrates these concepts.

184

Establishing a Datum Axis

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Circular Runout

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Circular runout is a composite control, that isa control for form, orientation and location ofcircular elements of a part feature.

A circular runout control is a geometrictolerance that limits the amount of circularrunout of a part surface.

Circular runout may control location or ifapplied to a diameter, the form and location ofa datum axis.

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Circular Runout

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The tolerance zone for circular runout is twocoaxial circles whose centers are located onthe datum axis.

The outer tolerance zone circle is establishedby the feature element farthest from thedatum axis. The inner circle is offset by thetolerance amount.

All surface elements must reside within thetolerance zone circles.

Figure 11-3 illustrates this187

Circular Runout Tolerance Zone

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Circular Runout

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Circular runout, being a composite control,measures several different errors with a singlemeasurement. Figure 11-4 illustrates thesevarious errors.

Each error is measured by a single reading.

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Circular Runout As CompositeControl

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Th f ll i li

Circular Runout Applications

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The following applies: Diameter must meet size requirements

WCB is affected

Runout control is applied RFS

Runout applies at each circular element of thetoleranced diameter

Tolerance zone is two coaxial circles separated bythe tolerance

Maximum possible axis offset is one half of therunout tolerance

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Circular Runout Applied To ADiameter

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Circular Runout

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Applied to a surface, the following applies: Control is applied at RFS

Runout applies to each circular element of the

surface

Tolerance zone is two coaxial circles offset by the

tolerance value

Control does not control orientation of the

surface

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Circular Runout Applied To A Surface

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Legal Specification For Runout Control

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Figure 11-7 is the flowchart for answering thequestions of a legal specification for runout.

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Verifying Circular Runout

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Must meet

rule 1boundary

Mustmeet size

limits

Total Runout

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A composite control that affects form,orientation and location of all surfaceelements, either a diameter or a surface,relative to a datum axis.

If applied to a diameter, the tolerance zone istwo coaxial cylinders with centers located onthe datum axis.

Figure 11-9 illustrates this principle.

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Total Runout

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Total Runout As A Composite Control

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Total runout limits cylindricity, orientation andaxis offset of a diameter.

TR does affect worst case boundary.

Again, the single reading will read three typesof part errors. Figure 11-10 illustrates thisprinciple.

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Total Runout Example

WhatEntire

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What

happens if wehave

combined axisand form

error?

Errorcould beform

error

could beaxis offset

Total Runout Application

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Diameter must meet size requirementsWCB is affected

Control is applied at RFS

Runout applies simultaneously to all surfaceelements

Tolerance zone is two coaxial cylinders

Maximum axis offset is one half the tolerancevalue

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Total Runout Applied To A Diameter

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Total Runout Applied To A Surface

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Control is applied at RFS Runout applies simultaneously to all surface

elements

Tolerance zone is two parallel planesperpendicular to datum axis

Runout controls the angular (orientation)

aspect of the surface to the datum axis Runout also controls the flatness

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Total Runout Applied To A Surface

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Why isflatness alsocontrolled?

Verifying Total Runout

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Runout may be applied to a diameter or asurface.

Legal specification for Total runout is the sameas runout.

Figures 11-13 and 11-14 illustrate how toverify total runout.

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Verifying Total Runout

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Verifying Total Runout

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Comparison between Circular andTotal Runout

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Figures 11-15 and 11- 16 illustrate how eachrunout control should be used and what couldhappen if not applied properly.

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Comparison Chart

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Comparison of Controls

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This is a calculation to find the max/min

Runout Calculations

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This is a calculation to find the max/mindistance on a part. When we calculate thesevalues all tolerances must be used.

This calculation in figure 11-17 is one exampleand may be used for circular or total runout.

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Runout Calculations

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Summary Chart

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Questions?

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Chapter Twelve

Profile Controls

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Understand profile tolerancing

Chapter Goals

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Understand profile tolerancing

Interpret the profile of a surface control

Interpret profile of a line control

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Profile controls may be specified with or

Profile Control Notes

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Profile controls may be specified with orwithout a datum reference.

If a datum is referenced, we have a related feature

control

If no datum is referenced, we have a form control

Form controls apply specifically where the surface

exist.

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A profile is the outline of a part feature in a

Profile

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A profile is the outline of a part feature in agiven plane.

A true profile is the exact profile of a part feature

as shown by basic dimensions.

A profile control is a geometric tolerance thatspecifies a uniform boundary along the trueprofile that the elements of the surface must

lie within.

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A profile line control applies to line elements

Profile

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A profile line control applies to line elementsof the toleranced surface.

The true profile must be located with basic ortoleranced dimensions relative to the datumsreferenced in the profile control.

Figure 12-2 illustrates these issues.

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Profile Control

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Profile of a surface has a tolerance zone for

Profile Tolerance Zones

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Profile of a surface has a tolerance zone forthe width, length and depth of the control.

Profile of a line tolerance zone is length andwidth. Applies for full length of surface.

All profile controls, whether surface or line,are bilateral with equal distribution.

Figure 12-3 has examples and exceptions.

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Profile Tolerance Zone

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A profile control, when pointing to a surface,

Profile Controls

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A profile control, when pointing to a surface,applies to the entire length and width of thesurface.

There are ways of extending or moderatingthe control.

Figure 12-4 shows these ways.

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Clear definition of the tolerance zone.

Advantages of Profile

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Communicates datums and datum sequence.

Eliminates accumulation of tolerances.

Figure 12-5 illustrates this.

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Advantages of profile

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A geometric tolerance that limits the amount

Profile Of A Surface Control

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gof error a surface can have relative to its trueprofile.

Applications include controlling size, location,

orientation, and form for: Planar, curved or irregular surfaces

Polygons

Cylinders, surfaces of revolution, or cones

Coplanar surfaces

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Profile & Tolerance Of A SurfaceLocation

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Profile And Conical Features

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Profile And A Conical feature

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If a basic dimension

was used to sizethe cone, theprofile would limit

the size of thecone

Profile and Coplanar surfaces

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Profile and Coplanar Surfaces

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Profile and Multiple Coplanar Surfaces

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Sometimes the form, size, orientation, and

Multiple Single-Segment Controls

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location tolerances need to be at differentlevels. Multiple single-segment controls arethen used. We have seen them before.

If a surface is toleranced differently relative todifferent datums, multiple controls must beused.

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Multiple Single-Segment Controls

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Appliedto trueprofile

Controls location

Controls orientationControls size & form

Multiple Single-Segment Controls

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Figure 12-12 is the flowchart for use.

Legal Specification For Profile

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Figure 12-6 illustrates one way to inspect

Inspecting Profile Of Surface

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surface profile. There are several others.

CMM

Optical

Surface profilometer

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Inspecting Surface Profile

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Similar to profile of a surface except tolerance

Profile Of A Line

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zone is two dimensional for a line whereas itis three dimensional for a surface.

Profile of a line control is a geometric

tolerance that limits the amount of error forline elements relative to their true profile.

Profile of a line controls in one direction. May

be used with multiple single-segment controlsor with profile of surface control.

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Profile of Line Example

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Profile of Line Example

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Profile of Line and a CT to ControlForm and Location

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Profile of Line and a CT to ControlForm and Location

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Figure 12-12 is the flowchart from which onef

Legal Specification For Profile of a Line

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can answer the question of whether or notone has used the profile of a line controlcorrectly.

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Inspecting Profile of a Line

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More Tolerance Stacks

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More Tolerance Stacks

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Summary

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Next WeeK

Total Semester Review. Bring Questions. Iam going to highlight important principles

but you need to ask the questions