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8/18/2013 1 Intellectual Design & Engineering

Geometric Dimensioning and Tolerancing

Tolerance of Position -- RFS

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.490 - .500

C

A

B

.014 A B C

The information in the feature

control frame would be read asfollows: Regardless of featuresize, this feature must be located on true position within acylindrical tolerance zone of .014in. on diameter, with referenceto datums A (primary),

B(secondary), and C (tertiary). Irrespective of how large orsmall the actual hole size is within its size limits noadditional tolerances areavailable for the location of thefeature. Ill demonstrate in thenext few slides.

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Form Tolerance


True Position

The exact location of the hole is established with basic dimensions.

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Form Tolerance


True Position

Location ToleranceZone RFS

The cylindrical tolerance zone is established in the featurecontrol frame ( .014).

.014 A B C

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True Position


(Always the Same)

.014 A B C

MMC Diameter

When the axis is located at theextreme limit of the tolerancezone, the MMC hole axiswould be offset from the true

position by a distance equal toone-half of the positiontolerance (.007).

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True Position

Location ToleranceZone RFS(Always the Same)

.014 A B C

MMC Diameter

The actual hole size may vary between MMC (smallestdiameter) and LMC (largestdiameter), but the axislocation cannot violate the

boundaries of its locationtolerance.

LMC Diameter



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True Position


.014 A B C

MMC Diameter

LMC Diameter

The white circle representsthe MMC boundary. Itscenter is located at true

position. No element of thehole surface can be insidethis boundary.

MMC Boundary(VC Functional Gaug



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8/348/18/2013 8 Intellectual Design & Engineering

True Position


.014 A B C

MMC Diameter

LMC Diameter

The outer white circle representsthe LMC boundary centered ontrue position. No elementson the surface of the holecan be outside of this

boundary. The

following series of Slides will sequenceThe progressive

position of the center of the hole asit moves around thetolerance zone.

LMC Boundary

MMC Boundary(VC Functional Gauge



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True Position


.014 A B C

MMC Diameter

LMC Diameter

The outer white circle represents theLMC boundary. No elementson the surface of the hole

can be outside of this boundary. The followingseries of slides will

sequence the progressive positionof the center of thehole as it movesaround the tolerancezone.

LMC Boundary




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True Position


.014 A B C

MMC Diameter

LMC Diameter

LMC Boundary



Tolerance of Position -- RFS The outer white circle represents theLMC boundary. No elementson the surface of the hole

can be outside of this boundary. The followingseries of slides will

sequence the progressive positionof the center of thehole as it movesaround the tolerancezone.

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True Position


.014 A B C

MMC Diameter

LMC Diameter

LMC Boundary




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True Position


.014 A B C

MMC Diameter

LMC Diameter

The outer whitecircle representsthe LMC boundary.

No elements on thesurface of the holecan be outside of this boundary. The

following series of slides willsequence the

progressive position of thecenter of the holeas it moves aroundthe tolerance zone.

LMC Boundary

MMC Boundary(VC Functional Gaug

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True Position


.014 A B C

MMC Diameter

LMC Diameter

LMC Boundary




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True Position


.014 A B C

MMC Diameter

LMC Diameter

LMC Boundary


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TOLERANCE OF POSITION ATMAXIMUM MATERIAL CONDITION


Tolerance of Position -- MMC

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The next example will illustrate the concept of bonustolerance, in connection with position tolerances. Wewill use the same drawing example that was used todiscuss tolerances of position, when applied regardlessof feature size (RFS). One of the significant differences

you will see is the advantages of defining the tolerancezone for the axis of a hole as we did before but thistime, we will add the modifier for maximum material condition (MMC) to the tolerance specification in the

feature control frame . Notice the changes that occur inlocation tolerances when modifiers are used, and asdeparture from MMC occurs.



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M

.490 - .500

.014 A B CC

A

B

The information in the featurecontrol frame would be read as

follows: This feature must belocated on true position within acylindrical tolerance zone of .014on diameter with reference todatums A (primary), B(secondary), and C (tertiary),when the hole is at its smallest size, or MMC.

As the actual hole size increasesin size from MMC, additionaltolerance (equal to the amountof departure) may be added tothe location tolerance for thefeature.



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True Position The exact location of thehole is established bybasic dimensions.



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True Position

MMC Diameter (Axis

at Maximum Offset)


The maximum materialcondition diameter of .490 isshown at its maximum offsetfrom true position one-half the specified locationtolerance.



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True Position

MMC Diameter


As the size of the holechanges within itstolerance range fromMMC smallest hole sizelimit, and increases in sizetowards the LMC, or uppersize limit, an equal amountof tolerance can be added to the axis location tolerance.

Location ToleranceZone at LMC



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True PositionMMC Diameter


Location Tolerance

Zone at LMC

The additionaltolerance for the holeaxis location (which isequal to the amountof departure fromMMC), is calledbonus tolerance.

LMCDiameter

Bonus Tolerance



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True Position

MMC Diameter



LMCDiameter

When the hole size is atits lower limit (MMC),and positioned at theextreme limit of theMMC location tolerance,the MMC boundary isestablished. When thefeature of size is at thislimit, no elements of thehole surface may beinside this theoreticalboundary. This is thevirtual condition of thehole, which alsosimulates the mating

part at its maximummaterial condition . MMC Boundary



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LMC

Diameter

MMC Boundary

When the hole sizeis at its upper limit(LMC), andpositioned at theextreme limit of the locationtolerance, the LMCboundary isestablished.No elements of the hole surfacecan be out-sidethis boundary.

LMC Boundary



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LMCDiameter

MMC Boundary(VC=MMC-Tol)

LMC Boundary

In this next series of

slides, note that while thesize and location of theactual hole may vary, theelements onthe surface of the holesnever violate theirboundaries. Thisseries will helpyou to understandhow the hole sizechanges can affectthe location of thecenter axis and its

orientation.


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Location Toleranceat MMC


Location Tolerance at LMC

LMCDiameter

MMC Diameter

True Position

LMC Boundary

Axis location variancepossibilities whenposition tolerance ismodified to MMC.

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LMCDiameter

MMC Diameter

True Position

LMC Boundary


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LMCDiameter

MMC Diameter True Position

LMC Boundary


d l

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LMCDiameter

MMC Diameter

True Position

LMC Boundary

G i Di i i d T l i

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LMCDiameter

MMC Diameter

True Position

LMC Boundary


G i Di i i d T l i

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LMCDiameter

MMC Diameter

True Position

LMC Boundary


G i Di i i d T l i

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LMCDiameter

MMC Diameter True Position

LMC Boundary


G t i Di i i d T l i

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Location Toleranceat MMCLocation Tolerance at LMC



LMCDiameter

MMC Diameter

True Position

LMC Boundary

Axis location

variance possibilitieswhen positiontolerance ismodified to MMC.

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