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PROCEDURE / DRAFTING FNHA-3-B-072.00 NAME STD GEO DIM & TOL ENGINEERING SPECIFICATION THE INFORMATION HEREON IS THE CONFIDENTIAL AND PROPRIETARY PROPERTY OF NEW HOLLAND NORTH AMERICA, INC. AND/OR NEW HOLLAND CANADA, LTD. ANY USE, EXCEPT THAT FOR WHICH IT MAY BE LOANED, IS PROHIBITED. FRAME OF 1 69 PART NUMBER 86508251 ALL C TD 111649 980310 ALL B EDF 110394 970723 REL A EDF 104739 950123 FRAME NO. REV BY ECN NO. DATE APP. DRAWN TD MAR 1998 KHH JUL 97 CHECKED GEOMETRIC DIMENSIONING AND TOLERANCING 1.0 INTRODUCTION 1.1 SCOPE This standard specifies and describes the principles of geometric dimensioning and tolerancing as applied to engineering drawings. 1.2 REFERENCES The following standards were used as reference to establish this standard. 1.2.1 ANSI Y14.5M 1.2.2 ISO 1101 1.3 INDEX Index to the various sections can be found on page two. 1.4 REPLACED STANDARDS This standard replaces the following company standard: Ford New Holland WS 49.06

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Page 1: GD&T

PROCEDURE / DRAFTING FNHA-3-B-072.00

NAMESTD GEO DIM & TOL

ENGINEERING

SPECIFICATION

THE INFORMATION HEREON IS THE CONFIDENTIAL

AND PROPRIETARY PROPERTY OF NEW HOLLAND

NORTH AMERICA, INC. AND/OR NEW HOLLAND

CANADA, LTD. ANY USE, EXCEPT THAT FOR

WHICH IT MAY BE LOANED, IS PROHIBITED.

FRAME OF1 69

PART NUMBER

86508251

ALL C TD 111649 980310

ALL B EDF 110394 970723

REL A EDF 104739 950123

FRAME NO. REV BY ECN NO. DATE

APP. DRAWN TD MAR 1998

KHH JUL 97 CHECKED

GEOMETRIC DIMENSIONING AND TOLERANCING

1.0 INTRODUCTION

1.1 SCOPE

This standard specifies and describes theprinciples of geometric dimensioning andtolerancing as applied to engineering drawings.

1.2 REFERENCES

The following standards were used as reference toestablish this standard.

1.2.1 ANSI Y14.5M

1.2.2 ISO 1101

1.3 INDEX

Index to the various sections can be found on pagetwo.

1.4 REPLACED STANDARDS

This standard replaces the following companystandard:

Ford New Holland WS 49.06

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ENGINEERING SPECIFICATIONREV.C

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OF69 86508251

INDEX

Section Title Page

1. Symbology .......................................................................................................................... 3

1.1 Geometric Characteristics and Symbols ............................................................................. 3

1.2 Other Symbols (Relating to Geometric Tolerancing) ........................................................... 3

1.3 Identifying the Tolerance Zone............................................................................................ 6

1.4 Feature Control Frame & Datum Feature Symbol Placement ............................................. 7

1.5 Use of Notes ....................................................................................................................... 7

2. Datum Referencing............................................................................................................. 8

2.1 Datum & Datum Feature ..................................................................................................... 8

2.2 Referencing Datums According to Importance.................................................................. 10

2.3 Datum Targets .................................................................................................................. 16

3. Tolerances of Form........................................................................................................... 21

3.1 Straightness Tolerance ..................................................................................................... 21

3.2 Flatness Tolerance ........................................................................................................... 24

3.3 Circularity (Roundness) Tolerance.................................................................................... 25

3.4 Cylindricity Tolerance........................................................................................................ 25

4. Tolerances for Profile Control ........................................................................................... 28

4.1 Profile Tolerance............................................................................................................... 28

5. Tolerances for Orientation Control .................................................................................... 35

5.1 Angularity Tolerance ......................................................................................................... 35

5.2 Parallelism Tolerance ....................................................................................................... 38

5.3 Perpendicularity Tolerance ............................................................................................... 41

6. Tolerances for Runout Control .......................................................................................... 47

6.1 Circular Runout Tolerance ................................................................................................ 47

6.2 Total Runout Tolerance .................................................................................................... 47

7. Tolerances of Location...................................................................................................... 52

7.1 Position Tolerance ............................................................................................................ 52

8. Free State Variation .......................................................................................................... 68

8.1 Specifying Circularity in a Free State with Average Diameter............................................ 68

8.2 Specifying Restraint for Non-rigid Parts ............................................................................ 69

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ENGINEERING SPECIFICATIONREV.C

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S

M

SYMBOLOGY

1. SYMBOLOGY. Wherever possible, the use of internationally accepted symbols is recommended rather thanthe use of notes. This eliminates the translation of notes into other languages and also eliminates the possibility ofmisinterpretation of the note. This section establishes the symbols for specifying geometric characteristics and otherdimensional requirements on engineering drawings in accordance with ANSI Y14.5M and ISO 1101.

1.1 GEOMETRIC CHARACTERISTICS AND SYMBOLS

TYPE OFTOLERANCE

SYMBOL CHARACTERISTICREFERTO

STRAIGHTNESS 3.1

FOR INDIVIDUAL FORM FLATNESS 3.2

FEATURES CIRCULARITY (ROUNDNESS) 3.3

CYLINDRICITY 3.4

FOR INDIVIDUAL OR PROFILE PROFILE OF A LINE 4.1.2

RELATED FEATURES PROFILE OF A SURFACE 4.1.2

ANGULARITY 5.1

ORIENTATION PERPENDICULARITY 5.3

FOR RELATED PARALLELISM 5.2

FEATURES RUNOUT CIRCULAR RUNOUT 6.1

TOTAL RUNOUT 6.2

LOCATION POSITION 7.1

CONCENTRICITY * ——

* THIS CHARACTERISTIC WILL NOT BE USED BY NEW HOLLAND

1.2 OTHER SYMBOLS (RELATING TO GEOMETRIC TOLERANCING)

REFER TO

OR DATUM FEATURE SYMBOL 1.2.1

DATUM TARGET SYMBOL 1.2.2

FEATURE CONTROL FRAME 1.2.3

DIAMETER (CYLINDRICAL TOLERANCE ZONE WHEN USED WITHFEATURE CONTROL SYMBOL) 1.3

MAXIMUM MATERIAL CONDITION (MMC) ** 1.2.4

REGARDLESS OF FEATURE SIZE (RFS) 1.2.5

PROJECTED TOLERANCE ZONE 1.2.6

BASIC (EXACT) DIMENSION

** FOR NEW HOLLAND APPLICATIONS UNLESS OTHERWISE SPECIFIED: POSITION TOLERANCE AND RELATEDDATUMS APPLY AT MMC. OTHER GEOMETRIC TOLERANCES APPLY RFS. NEW HOLLAND WILL NOT USE THESYMBOL ON DRAWINGS SINCE IT IS NOT INCLUDED IN THE ISO STANDARDS.

S

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ENGINEERING SPECIFICATIONREV.C

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1.2.1 Datum feature symbol

The datum feature symbol consists of a frame containing the datum identifying letter.The letter is preceded and followed by a dash. The symbol frame is associated to thedatum feature by one of the methods described in 1.4 for feature frames. Eachdatum feature requiring identification shall be assigned a different letter with theletters “I”, “O”, “Q”, and “X” omitted.

MIN. 5 MM GRAPHIC MIN. 8 MM BOARDMIN. .2 IN DRAWINGS MIN. .3 IN DRAWINGS

1.2.2 Datum target symbol

The datum target symbol is a circle divided horizontally into two halves. Thelower half contains a letter identifying the associated datum, followed by thetarget number assigned sequentially starting with 1 for each datum.

Where the datum target area is a circular area, the area size may be enteredin the upper half. Otherwise, the upper half is left blank.

Where the datum target is a point, the location is indicated by an “x” andthe other half of the datum target symbol is left blank.

1.2.3 Feature control frame. Geometric characteristic symbols, the tolerance value, and datum reference letters, whereapplicable, are combined in a feature control frame to express a geometric tolerance.

A geometric tolerance for an individual feature is specified by means of a featurecontrol frame divided into compartments containing the geometric characteristicsymbol followed by the tolerance.

MIN. 5 MMGRAPHIC MIN. 8

MM BOARDMIN. .2 IN DRAWINGS MIN. .3 IN DRAWINGS

Where applicable, the tolerance is preceded by the diameter symboland followed by the maximum material condition symbol.

* } }

}* }

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1.2.3 Feature control frame (continued)

Where a geometric tolerance is related to a datum, this relationship isindicated by entering the datum reference letter in a compartmentfollowing the tolerance.

Where a datum is established by two datum features (for example, an axisestablished by two datum diameters) both datum reference letters, separatedby a dash, are entered in a compartment.

Where more than one datum is required, the datum reference letters areentered into separate compartments in the desired order of precedence.

Datum reference letters need not be in alphabetical order in the featurecontrol frame.

A composite feature control frame is used where more than one toleranceis specified for the same geometric characteristic of a feature or featureshaving different datum requirements.

Where a feature or pattern of features controlled by a geometric tolerancealso serves as a datum feature, the feature control frame and datum featuresymbol are combined.

1.2.4 Maximum material condition (MMC)

The maximum material condition symbol is specified in a feature controlframe when the tolerance value is applied to the maximum material conditionof the associated feature.

h=

TEXT HEIGHT IN FEATURE

CONTROL FRAME

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1.2.4.1 Effect of maximum material condition. Where a geometric tolerance is applied a MMC, the tolerance is limited toits specified value if the feature is produced at its MMC limit of size. If the actual size of the feature is not its MMC, thenthe allowable tolerance will increase equal to the difference between the feature’s actual size and its MMC. This principlealso applies to a datum feature if it is referenced at MMC. The axis or centerplane of the datum feature may deviate fromthe axis or center plane of its datum by an amount equal to the difference between its actual size and its MMC.

1.2.4.2 Position tolerance and its related datums will apply at MMC unless otherwise specified. It is not required toshow the symbol in the feature control frame for this application since this note is specified in the general toleranceblock on all drawings.

1.2.5 Regardless of feature size (RFS). The symbol will not be used on drawings since it is not an acceptedworldwide symbol and may be eliminated.

1.2.5.1 Effect of RFS. Where a geometric tolerance is applied on a RFS basis, the tolerance is limited to its specifiedvalue regardless of the actual size of the feature. Likewise, referencing a datum feature on a RFS basis means that acentering about its axis or center plane is required, regardless of the actual size of the feature.

1.2.5.2 RFS applies to the geometric tolerance, datum reference or both where no material condition is specified unlessotherwise specified in the general tolerance block on the drawing.

1.2.6 Projected tolerance zone

Where a projected tolerance zone is applied to a position or orientationtolerance, a frame containing the projected tolerance zone symbolpreceded by the zone height is placed below the feature control frame.

1.3 IDENTIFYING THE TOLERANCE ZONE. The diameter symbol ∅will precede the tolerance value where the tolerance value represents the diameter of a cylindrical zone. No identificationsymbol is required where the tolerance zone is other than a diameter, as this tolerance value represents the distancebetween two parallel lines or planes, or the distance between two uniform boundaries.

M

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1.4 FEATURE CONTROL FRAME AND DATUM FEATURE SYMBOL PLACEMENT. To relate the feature controlframe and datum feature symbol to its associated feature, use one of the following methods.

(a) Add the feature control frame or datum feature symbol below or after a leader-directed callout or dimensiondirected to the feature.

(b) Use a leader from the feature control frame or datum feature symbol to the feature.

(c) Locate a side or end of the feature control frame or datum feature symbol on an extension line from thefeature if the feature is a plane surface.

(d) Locate a side or end of the feature control frame or datum feature symbol on an extension line of thedimension line relating to a feature of size.

1.5 USE OF NOTES. Situations may arise in which the geometric requirement desired cannot be totally defined byuse of symbols. In these situations a note may be used, either separately or to supplement a symbol, to describe therequirement.

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DATUM REFERENCING

2. DATUM REFERENCING. Where the geometric tolerance requirement of a feature is related to another feature orfeatures, a datum reference is used. This section defines methods of establishing those datums and the interpretation ofthem.

2.1 DATUM AND DATUM FEATURE

Surfaces of parts produced by normal manufacturing methodswill, if magnified, have some irregularity in the surface. Theactual part surface designated is the datum feature and thetrue geometric counterpart of that surface establishes thedatum. The datum is the origin of the dimensionalrelationship between the toleranced feature and the relatedfeature.

2.1.1 Datum feature selection. Datum features are selected to control the relationship between features of a part toinsure proper fit, function, and assembly of parts. Where practical, corresponding features on mating or related partsshould be selected as datum features. A datum feature should be accessible on the part and be of sufficient size forpractical usage.

2.1.2. Datums are used, as applicable, to control profile, orientation, runout, and location. Refer to 1.1.

2.1.3 Datum feature symbol placement

Application to a plane surface

Where a plane surface is to be used as a datum feature, the datumfeature symbol is located on an extension line directed to the surfaceor by a leader line directed to the surface. When using a triangle onan extension line to designate a plane surface, the triangle should notbe centered on a dimension line.

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2.1.3 Datum feature symbol placement (continued)

Application to a feature of size

Where the datum feature is a feature of size,whether a cylindrical surface or two parallelplanes, the datum feature symbol must be clearlyrelated to the size dimension or to the feature.When using a triangle to designate a feature ofsize, the triangle must be centered on thedimension line.

Partial surfaces as datum features

For some design requirements, only a portion of a surface is required to be designated as a datum feature. In thesesituations, a chain line located by basic dimensions is used to identify that portion of the surface.

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2.1.4 Compound datum features. Two datum features may be used to established a single datum. To accomplish this,each datum feature or portion of datum feature is designated with its own datum feature symbol. The datum referenceletters, separated by a dash, are then shown in a single compartment of the feature control frame.

A single datum plane can be established by simultaneously contacting the high points of two surfaces.

A single datum axis for two coaxial diameters can be established by simultaneously contacting the high points of bothsurfaces.

2.2 REFERENCING DATUMS ACCORDING TO IMPORTANCE. A feature can be referenced to up to three planesurfaces simultaneously if required. When this is done, and order of precedence must be defined in the feature controlframe according to the importance of each plane to the toleranced feature. This first datum referenced is the mostimportant or primary datum. The second datum referenced is the secondary datum and the third datum referenced is thetertiary datum. Refer to 1.2.3.

Datum reference frame

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2.2.1 Positioning a part on a datum reference frame. A part positioned on a datum reference frame must contact theprimary datum plane at a minimum of three points, the secondary datum plane at a minimum of two points, and the tertiarydatum plane at a minimum of one point.

Shown below is a part with two ∅ 7 07 2.. holes which must be located within ∅ 0.2 at MMC to a primary (D), secondary (E)

and tertiary (F) datum. To satisfy this geometric tolerance requirement, the finished part, when dropped over two ∅ 6.8

(∅ 7.0 MMC-0.2 total tol.) pins, must contact datum plane D a minimum of three points, datum plane E a minimum of two

points, and datum plane F a minimum of one point.

Shown below is an inspection fixture that would check thispart according to the specified geometric tolerance.

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2.2.2 Positioning parts with a cylindrical datum feature on a reference frame. The datum established by a cylindricalsurface is the axis of a true cylinder as established by inspection equipment. A cylindrical datum feature is alwaysassociated with two theoretical planes intersecting at right angles on a datum axis: therefore, a cylindrical datum featureuses two of the planes on a datum reference frame.

Shown below is a part with four ∅ 10 8112

.. holes which must be located within ∅ 0.8 at MMC to a primary (K) and secondary

(M) datum. To satisfy this geometric tolerance requirement, the finished part, when dropped over four ∅ 10 (∅ 10.8 MMC-

0.8 total tol.) pins, must contact datum plane K a minimum of three points and must fit within a ∅ 76.4 (MMC) datum M

boundary.

Shown is an inspection fixture that would checkthis part according to the specified geometrictolerance.

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2.2.3 Angular orientation. Where it is important to establish the angular orientation of a part about the datum axis, atertiary datum feature is referenced in the feature control frame.

In the example shown below, angular orientation of the two planes intersecting through datum B is established by thecenter plane of slot C, the tertiary datum feature.

The illustration below shows the development of the theoretical datum reference frame for the position tolerance shownabove.

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2.2.4 Effect of datum sequence and material condition. Where datums specified in sequence include a feature of size,the material condition at which the datum feature applies must be determined. The effect of its material condition andorder of precedence should be considered relative to the fit and function of the part. As previously stated, positiontolerances and their related datums will apply at MMC unless otherwise specified. Other geometric tolerances will applyRFS unless otherwise specified.

The illustration below shows the different effects that changing the material condition of the datum features and thesequence of the datum references has on the allowable finished part.

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2.2.4.1 Datum features designated RFS. Where a datum feature of size is designated as RFS, the datum is determinedby physical contact between the surface or surfaces of the feature and inspection tools.

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2.2.4.2 Datum features designated MMC. Where a datum feature of size is designated at MMC, the datum is theequivalent of the MMC limit of size of the datum feature.

2.3 DATUM TARGETS. Due to distortion caused by welding, forming, casting, etc., the entire surface of somefeatures cannot be used effectively to establish a datum. Where this condition arises, the important points, lines, or areasof contact of that feature should be used to define the datum for that feature. These points, lines, or areas are calleddatum targets.

2.3.1 Datum target symbols (Refer to 1.2.2)

Datum target points

The symbol “X” is used to indicate a datum target point on a surface. The “X” is located by dimensions on a direct view ofthe surface, or where there is no direct view it is located on two edge views.

Datum target lines

A datum target line is indicated by the symbol “X” on an edge view of the surface and a phantom line on the direct view.Where the length of the datum target line must be controlled, its length is dimensioned in the direct view.

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2.3.1 Datum target symbols (continued)

Datum target areas

Where it is necessary to designate areas of flat contact rather than points to assure proper establishment of a datum, atarget area of the desired shape is specified. The datum target area is indicated by section lines inside a phantom outlineof the desired shape. If the datum target area is a diameter, its size may be specified in the upper half of the datum targetsymbol; otherwise, the desired shape is controlled by dimensions on the drawing. Where a circular target area is too smallto show it on the drawing. it may be represented by an “X” and its diameter specified in the datum target symbol.

Single datum target areas (partial datums)

In some situations, one datum target area is of sufficient size to be used to determine the datum and is also the only areaof the surface that is important when referenced to a geometric tolerance. In such instances, that target area is shown anddimensioned on the drawing. The symbol should be used to designate it.

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2.3.2 Datum planes created by datum targets. A primary datum plane is established by at least three target points orareas not on a straight line or by at least three points of contact within a single datum target area. Secondary datum planesare established by two target points or areas, and tertiary datum planes are established by one target point or area.

The illustration below shows the establishment of a primary datum plane from three datum target areas.

2.3.3 Dimensioning datum targets. Locating dimensions and size dimensions, where required, can be expressed in theform of either basic dimensions or toleranced dimensions. Where basic dimensions are used, tooling or gaging tolerancesare assumed to apply.

The illustration below shows three perpendicular planes established by three points on the primary datum feature, twopoints on the secondary datum feature, and one point of the tertiary datum feature.

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2.3.4 Step datums. A datum plane may be established by targets located on stepped surfaces

In the illustration below, a basic (gage) dimension defines the offset between the target points while a toleranceddimension controls the distance between the surfaces.

2.3.5 Circular target lines and cylindrical target areas. On rotating cylindrical parts, it is sometimes necessary to applythe geometric tolerance for a feature to only a portion of or circular line on a cylindrical datum surface. In these situations,a circular target line or cylindrical target area should be designated. An example of this would be the bearing area of ashaft.

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2.3.6 Restraining of parts to a datum plane. Restraining is the application of a force to the free state condition of a partin order to simulate its actual assembled condition. In some situations, it is important to tolerance a feature of a part to thepart’s restrained condition rather than its free state condition. This is accomplished by adding a note to the feature controlframe.

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TOLERANCES OF FORM

3. TOLERANCES OF FORM. This section defines the methods of dimensioning and tolerancing to control the formof a feature or element of a single feature. Since form tolerances apply only to a single (individual) feature or element of asingle feature, they are not related to datums. The geometric form characteristics are straightness, flatness, roundness(circularity), and cylindricity. (Refer to 1.1)

3.1 STRAIGHTNESS TOLERANCE. Straightness is a condition where an element of a surface or an axis is a straightline. A straightness tolerance specifies a tolerance zone within which the considered element or axis must lie. Thestraightness tolerance is shown in the view where the elements to be controlled appear as a straight line.

3.1.1 Straightness — individual line elements

A straightness tolerance directed by a leader to the surface of the feature controlsindividual line elements of the surface. This control requires each line element to bewithin two parallel straight lines, separated by the specified tolerance.

Example

In the example to the right, each line element of the surface must lie withintwo parallel lines (0.02 apart) where the two lines and the nominal axisshare a common plane. The feature must always be within the specifiedlimits of size and the boundary of perfect form at MMC. The allowabledeviation from straightness will become less than the specifiedstraightness tolerance (for example, when the actual size of the feature is∅ 19.99, the straightness deviation is 0.01 maximum).

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3.1.2 Straightness — axis control

A straightness tolerance directed to a size dimension, either byattachment to the dimension line or by placement immediately adjacentto the dimensional value, controls the straightness of the axis of thefeature. This control requires the axis of the feature to lie within acylindrical tolerance zone equal in diameter to the tolerance. Thismethod permits the straightness tolerance to exceed the MMC limit ofsize.

Example — straightness of a feature of size — RFS (recommended)

Where a straightness tolerance is applied to a feature of size RFS, theaxis or centerline of the actual feature size must lie within the specifiedcylindrical tolerance zone (∅ 0.04). Additionally, each circular elementof the surface must be within the specified limits of size. NOTE —Straightness tolerance always applies RFS unless otherwise specified.

Example — straightness of a feature of size — MMC

Where a straightness tolerance is applied to a feature of size atMMC, the axis or centerline of the actual feature must lie withinthe specified cylindrical tolerance zone (∅ 0.04) at MMC. As thefeature departs from MMC, the allowable straightness toleranceincreases equally to the feature’s departure from MMC. See thechart for examples. Additionally, each circular element of thesurface must be within the specified limits of size.

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3.1.3 Straightness — unit length and total. In order to prevent an abrupt surface variation over a relatively short lengthof a feature, a straightness tolerance may be applied on a unit basis. When using unit control, a maximum straightnesstolerance for the feature should always be specified because of the large variation that could occur if not controlled overall.

Example — straightness per unit length and total — RFS

In this example, the diameter of the tolerance zone over any20 mm length of the feature is 0.01 while the diameter ofthe tolerance zone over the total length of the feature is0.04. Additionally, each circular element of the surfacemust be within the specified limits of size.

3.1.4 Straightness — plane surfaces

Straightness may be applied to control line elements in asingle direction or two directions on plane surfaces. It isdesignated by a leader line in a direct view of the surfacethat shows the direction the tolerance is to be applied. Inthis example, each longitudinal element of the surface mustlie between two parallel lines 0.05 apart in the left view and0.1 in the right view.

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3.2 FLATNESS TOLERANCE. A flatness tolerance defines the permitted deviation of a surface from a theoreticallyflat plane.

The feature control frame for a flatness tolerance is attached to a surface byeither a leader line directed to the surface or by locating it on an extension lineto the surface.

Example

In this example all the surface variation must lie within two parallelplanes separated by the specified flatness tolerance (0.08).

If the surface is associated with a size dimension, the flatnesstolerance may not exceed the size tolerance.

3.2.1 Flatness — unit area and total. In order to prevent an abrupt surface variation in a relatively small area of afeature, a flatness tolerance may be applied on a unit basis. When using unit control, as flatness tolerance for the entirefeature should also be specified because of the large variation that could occur if not controlled overall.

Example

In the feature control frame to the right, any 30×30 area of the surface it is directedto would have to lie between two parallel planes. 0.1 apart, and the entire surfacewould have to lie between two parallel planes 0.4 apart.

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3.3 ROUNDNESS (CIRCULARITY) TOLERANCE. A roundness tolerance defines the permitted deviation of anycircular element of a feature from a theoretically true circle. Any circular element must lie between two concentric circleswhose radius difference is equal to the specified tolerance.

Example

In this illustration, each circular element of thesurface must lie within two concentric circles,one having a radius 0.25 greater than theother. Additionally each circular element ofthe surface must be within the specified limitsof size. Also, the roundness tolerance maynot exceed the size tolerance.

3.4 CYLINDRICITY TOLERANCE. A cylindricity tolerance defines the permitted deviation of any circular element of acylindrical feature from a theoretically perfect cylinder. Any circular element of the feature must lie between two concentriccylinders whose radius difference is equal to the specified tolerance.

Example

In this illustration, the cylindrical surface must lie between twoconcentric cylinders, one having a radius 0.25 larger than the other.Additionally, the surface must be within the specified limits of size.Also, the cylindricity tolerance may not exceed the size tolerance.

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3.5 EXAMPLES WITH FORM TOLERANCES APPLIED

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3.6 EXAMPLE WITH FORM TOLERANCES AND RUNOUT TOLERANCES APPLIED

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TOLERANCES FOR PROFILE CONTROL

4. TOLERANCES FOR PROFILE CONTROL. This section defines methods of dimensioning and tolerancing tocontrol the profile (outline) of a part or portion of a part. This control can be applied to either a single line element on theprofile surface or to the entire surface.

4.1 PROFILE TOLERANCE. A profile tolerance defines a tolerance zone controlling the form of line elements orsurfaces of a part outline or portion of a part outline as related to its own perfect counterpart. This control can be appliedto a related datum if applicable.

4.1.1 Application of profile tolerances

Dimensions

Basic dimensions are used to dimension the outline or portion of the outlineto which profile tolerances apply. These basic dimensions represent thetrue geometric shape to which the profile tolerance is applied. Where thereare many basic dimensions, the note “untoleranced dimensions are basic”may be used and the boxes around the dimensions may be omitted.

Line element control

A line profile tolerance directed by a leader to the part outline controlsindividual line elements of the part outline on the part surface.

Total surface control

A surface profile tolerance directed by a leader to the part outline controlsthe total surface of the part outline.

All around or between points

Where the profile tolerance applies to the entirepart periphery, the symbol ∅ is applied to theleader. See (a). If the tolerance applies to only aportion of the part periphery, it should bedesignated as shown in (b).

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4.1.1 Application of profile tolerances (continued)

Profile tolerance — no datum reference

Where profile tolerancing is used only for feature form control, no datumreference is specified. This indicates that the feature is to be compared toits perfect counterpart without any positioning to a datum.

Profile tolerance with datum reference

Where a profile tolerance for a feature or features is related to anotherfeature, that other feature should be specified as a datum. This requiresthe tolerance zone to be fixed in orientation to that datum.

Bilateral tolerance zone

Where no indication of tolerance zone is shown on the drawing, the profiletolerance is understood to be a bilateral tolerance. This means that thetolerance zone is centered on the perfect profile of the feature or features.

Unilateral tolerance zone

Where the tolerance zone is to apply to either one side or the other of theperfect profile, the zone is indicated by a phantom line adjacent to the sideof the profile that the tolerance zone is to be on and by arrowheadsindicating the zone. The phantom line should be drawn parallel to theprofile and need only be long enough to clearly indicate to which side of theprofile the tolerance must be.

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4.1.2 Interpretation of profile tolerances

Profile of a line element

Where a line profile tolerance is specified,any line element of the designated surfacemust lie within the specified tolerance zone(0.3).

Profile of a surface

Where a surface profile tolerance isspecified, the entire surface that isdesignated must lie within the specifiedtolerance zone (0.3).

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4.1.3 Profile tolerances in part applications

Profile toleranced surface located by a toleranced dimension

Where a profile toleranced surface islocated by a toleranced dimension only,the profile tolerance zone (0.3) may lieanywhere within the tolerance zoneestablished by the locating dimension(±1). The actual surface profile must liewithin the profile tolerance zone (0.3).

Profile toleranced surface located by a toleranced dimension and related datum

Where a profile toleranced surface islocated by a toleranced dimension andreferenced to a datum, the profiletolerance zone (0.3) may lie anywherewithin the tolerance zone established bythe locating dimension (±1) but mustmaintain its orientation to the referenceddatum ( ). The actual surface profilemust lie within the profile tolerance zone(0.3).

Profile tolerance for coplanar surfaces

Where two or more surfaces have all their elements in one plane, theflatness of that total plane can be controlled by a surface profile note.The profile tolerance establishes a tolerance zone (0.1) defined by twoparallel planes within which all elements of the indicated surfacesmust lie.

– A –

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4.1.3 Profile tolerances in part applications (continued)

Profile toleranced surface located by a basic dimension to datum surface

Where a profile toleranced surface is locatedby a basic dimension, the profile tolerancecan be applied either bilaterally or unilaterally.

Where a bilateral profile tolerance is appliedto a feature or features, the tolerance zone(0.3) is equally disposed about the true profileof the designated surface at the basicdimension.

Where a unilateral profile tolerance is appliedto a feature or features, the tolerance zone(0.3) is all located to either the outside orinside of the true profile of the designatedsurface at the basic dimension.

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4.1.3 Profile tolerances in part applications (continued)

Profile tolerance all around

Where a profile tolerance is applied allaround (∅ ), the tolerance can be appliedbilaterally or unilaterally (the illustration showsa bilateral tolerance). The actual outsidesurface profile must lie within the specifiedtolerance zone (0.8).

Where it is necessary to relate the tolerancezone to another surface, that surface can bespecified as a datum.

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4.1.3 Profile tolerances in part applications (continued)

Profile tolerances to control alignment

Where two or more parts are shown to align in a weld assembly or assembly, the allowable misalignment (determined bydesign and function) can be one of three conditions. Bilateral and unilateral profile tolerances can be used to expressthese allowable conditions.

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TOLERANCES FOR ORIENTATION CONTROL

5. TOLERANCES FOR ORIENTATION CONTROL. This section defines methods of tolerancing to control theorientation of features to other features. The orientation tolerances are angularity, perpendicularity, and parallelism. Theymay also be referred to as attitude tolerances. When specifying orientation tolerances, the considered feature is related toone or more datum features. Orientation tolerances apply RFS unless otherwise specified.

5.1 ANGULARITY TOLERANCE. Angularity is the condition of a surface or axis at a specified angle (other than 90º)from a datum plane or axis. The angularity tolerance is the distance between two parallel planes, inclined at the specifiedangle to a datum plane or axis, within which the tolerance surface or axis must lie.

5.1.1 Application of angularity control

Angularity for a plane surface

Where an angularity toleranced surface is located by a toleranced dimension, the angularity tolerance zone (0.3) may lieanywhere within the tolerance zone established by the dimension, but must maintain its relationship to the referenceddatum ( ). The actual profile of the surface must lie within the angularity tolerance zone (0.3).

Angularity for an axis (RFS)

Where an angularity tolerance is applied to a feature of size, the axis or centerplane of that feature of size may lieanywhere within the tolerance zone (0.5) established by the angularity tolerance in relationship to the referenced datum.

– A –

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5.1.1 Application of angularity control (continued)

Loose control of angularity between features

For drawing purposes, features are sometimes shown on the same centerline or at 90º when in actual function a liberalangular relationship is allowable between those features. In such cases, the angular tolerance may be expressed indegrees instead of decimals.

Position of these features in relation to the axis of the shaft is controlled by the standard shop practices manual: however,if a tolerance different from that specified in the standard shop practice manual is required, it must be specified in the formof an additional positional (!) tolerance.

No control of angularity between features.

Where the angularity between features may vary freely,a symbol may be used to designate that no angularitycontrol is needed.

Angularity control between some features

On some parts the angularity between some featuresmust be controlled while the angularity between othersmay vary freely. This can be designated as shown.

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5.1.1 Application of angularity control (continued)

No angularity control specified

Where features are located on centerlines and noangularity control is specified, the angular relationshipbetween the features shall be ±1º.

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5.2 PARALLELISM TOLERANCE. A parallelism tolerance defines the permitted deviation from a theoretically exactparallel condition.

A parallel tolerance specifies:

A tolerance zone defined by two planes or linesparallel to a datum plane or axis within which theconsidered feature (axis or surface) must lie.

A cylindrical tolerance zone parallel to a datumaxis within which the axis of the considered featuremust lie.

5.2.1 Application of parallelism control

Parallelism tolerance defined by two planes

Where a parallelism tolerance for a surface or line isreferenced to a datum surface, the designated line or surfacemust lie totally within the tolerance zone established by twoparallel planes separated by the specified tolerance. Thistolerance zone in turn may lie anywhere within the sizedimension of the part but must always remain parallel to thereferenced datum.

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5.2.1 Application of parallelism control (continued)

Parallelism tolerance defined by two planes (continued)

Where a parallelism tolerance for an axis is referenced to adatum surface, the designated axis must lie totally within thetolerance zone established by two parallel planes separatedby the specified tolerance. This tolerance zone in turn may lieanywhere within the size dimension of the part but mustalways remain parallel to the referenced datum.

Parallelism tolerance defined by a cylindrical tolerance zone

Where a parallelism tolerance for anaxis is referenced to a datum axis, thetoleranced axis must lie totally within acylindrical tolerance zone equivalent tothe specified tolerance. This cylindricaltolerance zone in turn may lieanywhere within the size dimension ofthe part but must always remainparallel to the referenced datum.

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5.2.1 Application of parallelism control (continued)

Parallelism tolerancing at MMC (effect of MMC)

Where a parallelism tolerance is applied to a feature of sizeat MMC, the tolerance zone within which the axis orcenterplane of the feature of size must lie is the specifiedtolerance when the feature of size is at its MMC. As thefeature of size departs from its MMC, the tolerance zoneincreases; however, the tolerance zone still must lie withinthe size dimension of the part and must always remainparallel to the referenced datum.

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5.3 PERPENDICULARITY TOLERANCE. A perpendicularity tolerance defines the permitted deviation of a surface,axis, or centerplane from a theoretically exact 90º datum plane or axis. A perpendicularity tolerance specifies:

A tolerance zone defined by two parallel planesperpendicular to a datum plane within which the surface ofa feature must lie.

A tolerance zone defined by two parallel planesperpendicular to a datum plane within which the centerplaneof a feature of size must lie.

A tolerance zone defined by two parallel planesperpendicular to a datum axis within which the axis of afeature of size must lie.

A cylindrical tolerance zone perpendicular to a datum planewithin which the axis of a feature of size must lie.

A tolerance zone defined by parallel, straight linesperpendicular to a datum plane or datum axis within whichan element of the surface must lie (radial perpendicularity.)

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5.3.1 Application of perpendicularity control

Plane surface to a datum plane

Where a perpendicularity tolerance for a surfaceor line is referenced to a datum surface, thedesignated surface or line must lie totally within thetolerance zone established by two parallel planesseparated by the specified tolerance and at 90º tothe referenced datum. This tolerance zone mustlie within the size dimension of the part.

Plane surface to two datum planes

Where a perpendicularity tolerance for asurface is referenced to two datum surfaces,the surface must lie within the specifiedtolerance zone perpendicular to each datumwhen the part is resting on at least three pointson the primary datum plane and touching atleast two points on the secondary datumplane. This tolerance zone must also lie withinthe size dimension of the part.

Feature of size (rect.) to a datum plane

Where a perpendicularity tolerance for a rectangularfeature of size is referenced to a datum plane, thecenterplane of that feature must lie within thetolerance zone established by two parallel planesseparated by the specified tolerance and at 90º to thereferenced datum. Also, the feature centerplane mustbe within the location dimension.

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5.3.1 Application of perpendicularity control (continued)

Feature of size to a datum axis

Where a perpendicularity tolerance fora cylindrical feature of size isreferenced to a datum axis, the axis ofthat feature of size must lie within thetolerance zone established by twoparallel planes separated by thespecified tolerance and at 90º to thereferenced datum axis. Also, the axisof the feature must lie within thelocation dimension.

Perpendicularity for an axis at a projected height

In some situations (holes for dowelpins, tapped holes for bolts, etc.) itmay be necessary to control the axis ofa hole for a distance beyond the datumsurface equal to the thickness of themating part. This is accomplished byspecifying a perpendicularity toleranceat a projected height. The feature axismust lie within the specified cylindricaltolerance zone which is perpendicularto and projects from the referenceddatum plane for the specified height.Also, the axis of the feature over theprojected height must lie within thelocation dimension.

NOTE: The perpendicularity tolerance does not control the intersection of thefeature axis and the datum axis. If this control is required, a position toleranceshould be used instead. See 7.1.3.

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5.3.1 Application of perpendicularity control (continued)

Cylindrical feature of size to a datum plane

Where a perpendicularity tolerance for acylindrical feature of size is referencedto a datum plane, the axis of that featuremust lie within the specified cylindricaltolerance zone which is at 90º to thereferenced datum plane. Also, the axisof the feature must lie within the locationdimension.

Perpendicularity for a line element of a surface to a datum plane

Where a perpendicularity tolerance is applied to any line element of a surface in relationship to a referenced datum plane,any line on that surface must lie within the specified tolerance zone which is perpendicular to the referenced datum plane.Also, any line element of the surface must lie within the location dimension. This approach can also be used to controlperpendicularity of radial elements to a datum axis.

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5.3.1 Application of perpendicularity control (continued)

Perpendicularity tolerancing at MMC (effect of MMC)

Where a perpendicularity tolerance is applied to a cylindrical feature of size atMMC and referenced to a datum plane, the axis of the feature must lie within acylindrical tolerance zone that is perpendicular to the datum plane. The diameterof the cylindrical tolerance zone is the specified perpendicularity tolerance whenthe feature is at its MMC. As the feature departs from its MMC, the diameter ofthe cylindrical tolerance zone increases accordingly.

Shown to the right is an inspection gage that would check this part.

5.4 CONTROL OF FLATNESS BY ORIENTATION TOLERANCES. Where an orientation tolerance (angularity,parallelism, or perpendicularity) is applied to a plane surface, the flatness of that surface is also controlled within thetolerance zone specified by the orientation tolerance. An additional flatness tolerance is specified only where a morelimiting flatness control of that surface is required.

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5.5 EXAMPLES WITH ORIENTATION TOLERANCES

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TOLERANCES FOR RUNOUT CONTROL

6. TOLERANCES FOR RUNOUT CONTROL. This section defines methods of tolerancing to control the runout of afeature or single element of a feature to another feature or combination of features. The features controlled by runouttolerances are located either around a datum axis or perpendicular to a datum axis. A datum is always required. Therunout tolerances are circular runout (single element of a surface) and total runout (total surface). Runout tolerancesalways apply RFS.

6.1 CIRCULAR RUNOUT TOLERANCE. A circular runout tolerance specifies the maximum allowable deviation fromperfect form of a line element of a surface as it rotates 360º about a datum axis.

6.2 TOTAL RUNOUT TOLERANCE. A total runout tolerance specifies the maximum allowable deviation from perfectform of an entire surface as it rotates 360º about a datum axis.

6.3. ESTABLISHING DATUMS FOR MEASURING RUNOUT

Datums for measuring runout should be selectedaccording to the function of the part. Generally fora shaft they will be the bearing diameters, sincethey determine the center of rotation of the shaft inactual application.

Where the shaft is supported by two bearings on thesame diameter, the datum for measuring runoutshould be designated by datum targets centered onthe bearing mounting area. This will simulate actualpart function.

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6.4 FULL INDICATOR MOVEMENT — CIRCULAR RUNOUT AND TOTAL RUNOUT

Runout is the full indicator movement (FIM) of a measuring device asthe part is rotated on its datum axis. Reading direction is takennormal (90º) to the toleranced surface.

NOTE: FIM is the term used internationally and should replace totalindicator reading (TIR) which is a United States term.

Circular runout is the FIM on a single location on the surface over onerevolution.

Total runout is the FIM as the indicator traverses the total surfacewhile maintaining the normal attitude, measuring one continuoustolerance zone.

NOTE: Total runout also controls straightness of the feature withinthe continuous tolerance zone.

6.5 APPLICATION OF CIRCULAR RUNOUT

Circular runout can be applied to a cone, a perpendicular planesurface, or a radiused groove in addition to a cylinder. In theillustration shown, each circular line element taken normal (90º) tothe indicated surfaces must lie within 0.05 FIM when the part isrotated 360º on datum axis A–B.

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6.6 APPLICATION OF TOTAL RUNOUT

Where total runout is applied to a cylindrical surface, theentire surface must lie within the specified total runouttolerance when rotated on the datum axis. In the illustrationshown, the entire surface must lie within 0.1 FIM while thepart rotates on datum axis A and the indicator transversesthe total surface and maintains normal attitude. This sameprocedure applies to conical surfaces and again the indicatortransverses the total surface maintaining normal (90º)attitude to it.

Total runout applied to datum surfaces

Where datum features are required by function to be included in the runout control, runout tolerances must be specified forthese features. This will indicate any misalignment of the individual datum feature axes to each other. In the illustrationshown, the entire surface of each datum feature must lie within 0.02 FIM while the part rotates on datum axis A–B.

Total runout can also be applied to a portion of a surface asshown to the right.

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6.6 APPLICATION OF TOTAL RUNOUT (continued)

Plane surfaces perpendicular to a datum axis

Where total runout is applied to a plane surface that is perpendicular toa datum axis, the entire surface must lie within the specified totalrunout tolerance when rotated on the datum axis. In the illustrationshown, the entire surface must lie within 0.1 FIM while the part rotateson datum axis A and the indicator transverses the total surface andmaintains normal attitude.

NOTE: The concavity and convexity of this surface is also controlledwithin the specified total runout tolerance.

6.7 APPLICATION OF RUNOUT CONTROL TO MULTIPLE DATUMS

A multiple datum for runout control may be used as follows:

In some situations due to part function it is importantto control runout to a plane surface as well as to anaxis. This is illustrated by the example to the right.

In other situations, the cylindrical surface referencedas a datum may be of insufficient length to properlydetermine a datum axis so a plane surface is used inconjunction to it to properly orient the part. This isillustrated by the example to the right.

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6.8 EXAMPLES OF RUNOUT TOLERANCES

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TOLERANCES OF LOCATION

7. TOLERANCES OF LOCATION. This section defines methods of tolerancing to control the location of a feature ofsize in relationship to another feature. The tolerances of location are position, concentricity, and symmetry; however theonly one used by New Holland will be position.

7.1 POSITION TOLERANCE. A position tolerance defines a zone within which the center, axis, or centerplane of afeature of size is permitted to vary from its theoretically exact position. Position tolerancing provides a method of locationto ensure assemble-ability and interchangeability at maximum tolerance.

7.1.1 Conventions related to positional control

Exact relationship

Basic dimensions are used to establish the exact location of thetolerance zone of a feature of size to its datum or to another positiontoleranced feature of size.

Features shown at 90º have an implied exact 90º relationship betweentheir tolerance zones when a position tolerance is specified.

Material condition

All position tolerance will be applied at MMC for the designated features ofsize and their related datums unless otherwise specified. A note is includedin the title block of each drawing stating this. The symbol will not be usedwith the feature control frame for position tolerance since through use of thenote it is understood to apply.

Tolerance zone

Where the symbol ∅ precedes the tolerance value, the tolerance zone iscylindrical in shape.

Where no ∅ symbol is specified, the tolerance value represents the distancebetween two parallel planes.

M

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7.1.2 Benefit of position tolerancing

Coordinate system versus position system

The top figure shows a part dimensioned by the coordinatesystem. Under this system the tolerance zone within whichthe axis of the hole must lie is a square (or rectangular)zone equivalent to the specified dimensional tolerance.This tolerance zone must be small enough so that hardwarewill always fit between it and its mating part when both areat MMC. This tolerance zone is constant and does notincrease as the holes depart from MMC, so the potential forincreasing tolerance is not used.

The bottom figure shows the same part dimensioned by theposition system. Under this system the tolerance zonewithin which the axis of the hole must lie is a cylindricalzone specified by a position tolerance. The diameter of thetolerance zone can be equivalent to the across cornerdimension of the coordinate tolerance, thus providing 57%additional tolerance at MMC in the four segments of thediameter as shown. Additionally, as the holes depart fromMMC toward their LMC, the diameter of the tolerance zoneincreases accordingly. This provides “BONUSTOLERANCE” without affecting fit up to mating parts.

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7.1.2 Benefit of position tolerancing (continued)

Further illustration

The top figure further illustrates the allowable location ofthe holes in the part shown on the previous page.

The bottom figures show a gage that would check thehole location to the allowable tolerance. Functionalgaging techniques are fundamentally based on theMMC position concept; however gages are notmandatory to fulfill MMC position inspection.

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7.1.3 Application of position tolerance

Series of holes

Where a series of holes are located by a position tolerance, the axis of each hole when at MMC must lie within acylindrical tolerance zone equivalent to the specified tolerance diameter. Each cylindrical tolerance zone must becentered on the perfect center distance between holes. As the holes depart in size from MMC toward their LMC, thediameter of the cylindrical tolerance zone will increase accordingly.

Additionally

A series of holes that are position toleranced toeach other can also be position toleranced to datumfeatures by the use of a composite feature controlframe. In such situations, the centers of thosezones in relationship to each other must fall withinthe cylindrical tolerance zones established inrelationship to the referenced datums. The centersof the holes must fall simultaneously within bothtolerance zones.

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7.1.3 Application of position tolerance (continued)

Series of holes (continued)

Where the same tolerance is required between holes in a series and between those holes and other features, a singlefeature control frame can be used with the related features referenced as datums. In such situations, the axis of each holeat MMC must lie within a cylindrical tolerance zone equivalent to the specified position tolerance. Each cylindricaltolerance zone must be centered on its perfect location in relationship to the datum features. As the holes depart in sizefrom MMC toward their LMC, the diameter of the cylindrical tolerance zone will increase accordingly.

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7.1.3 Application of position tolerance (continued)

Bolt circle — punched holes

It is a common practice for a number of holes to belocated on a bolt circle that shares a common axiswith a related cylindrical feature of size. In suchsituations, a position tolerance will be assigned tothe holes on the bolt circle with the relatedcylindrical feature referenced as a datum. In theexample to the right, the axis of each hole at MMCmust lie within the specified cylindrical tolerancezone which is centered on perfect dimensions inrespect to datum plane A and the MMC of datum D.As the holes depart in size from MMC toward theirLMC, the diameter of the cylindrical tolerance zonewill increase accordingly. Also as the diameter ofdatum feature D departs from MMC toward LMC,the allowable position will be affected.

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7.1.3 Application of position tolerance (continued)

Bolt circle — punched holes (continued)

The figures to the right show a gage that wouldcheck the hole locations of the part on the previouspage to the referenced datums by the allowabletolerance.

Additionally

*NOTE: (See preceding page also.) If theangular rotation of the hole pattern to otherpart features is not critical, it will be controlledby the implied 90º angle with the angulartolerance specified in the title block applied.If a more restrictive tolerance to controlrotation to a part feature is required, thatfeature should also be referenced as adatum. See the example to the right.

The figures to the right show a gage thatwould check the hole locations in the abovepart to its position tolerance.

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7.1.3 Application of position tolerance (continued)

Bolt circle referenced to a machined datum

Where holes on a bolt circle are positiontoleranced to a machined feature of size, thevirtual condition of that feature of size must beconsidered. Shown to the right is an example ofsuch a part and shown below is an example of agage to check the part.

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7.1.3 Application of position tolerance (continued)

Projected tolerance zone

Where the variation in perpendicularity of a threaded hole or dowel pin hole could cause interference between the screw orpin and the mating part, a projected tolerance zone may be specified. Where a projected tolerance zone is specified, theprojected axis of the hole must lie within the specified cylindrical tolerance zone for the height above the part surface thatis specified with the feature control frame. The leader for the callout must be directed to the side of the part that theprojected zone must be. A projected tolerance zone should be considered when the mating part is of sufficient thicknessthat an assembly problem could exist.

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7.1.3 Application of position tolerance (continued)

Coaxial features

Where a cylindrical feature is given a position toleranceto a cylindrical datum that shares the same axis, theaxis of that feature at MMC must lie within the specifiedcylindrical tolerance zone. That cylindrical tolerancezone is centered on the axis of the datum feature atMMC.

As the toleranced feature or datum feature depart fromMMC toward their LMC, the cylindrical tolerance zonewill increase accordingly. Shown below is a gage thatwould check this part according to the specifiedtolerance and the illustration of the worst allowablemisalignment condition of the axis of the two bores.

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7.1.3 Application of position tolerance (continued)

Coaxial features

Where cylindrical features of the same diameter areshown on a common axis with a position toleranceto each other, a pin equal to the MMC of thefeatures minus the specified ∅ tolerance zone mustpass through all features simultaneously.Additionally, each feature must lie within thespecified dimensional tolerance.

Additionally

The position tolerance shown above controls onlythe size of pin that the holes must accept. It doesnot control the relationship of the axis of the holestogether to the rest of the part any closer than thedimension tolerances. If a tighter relationship toanother feature is required, an orientationtolerance can be added and referenced to therelated feature. In the example to the right, theaxis of both holes together must lie within a 1 mmtolerance zone to datums A and B.

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7.1.3 Application of position tolerance (continued)

Coaxial features (continued)

The same method can be used to positiontolerance cylindrical features of unequaldiameter that are shown on a common axis.In this situation however, the note “2 holestogether” must be included with the featurecontrol frame. A step pin equal to the MMC ofeach feature minus the specified ∅ tolerance

zone must pass through all featuressimultaneously. Additionally, each featuremust lie within the specified dimensiontolerance.

Additionally

As on the previous page, the position toleranceshown above controls only the size of pin thatthe holes must accept. It does not control therelationship of the axis of the holes together tothe rest of the part any closer than thedimension tolerances. If a tighter relationship toanother feature or features is required, anorientation tolerance can be added to the axisand referenced to the related feature or features.In the example to the right, the axis of both holestogether must lie within a ∅ 1 mm tolerancezone to datums A and B.

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7.1.3 Application of position tolerance (continued)

Bidirectional position tolerancing

Where the allowable tolerance between features isdifferent in one direction than the allowable tolerancein its perpendicular direction, position tolerances canbe specified bidirectionally. As illustrated in thefigures to the right, the center of the slots must liewithin a rectangular tolerance zone equivalent to thespecified position tolerances when the holes are atMMC. This tolerance zone is centered on thecenterplanes of the datum features. As the slotsdepart from MMC toward their LMC, the tolerancezone will increase accordingly.

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7.1.3 Application of position tolerance (continued)

Holes in shafts

Where a hole in a shaft is position toleranced to the O.D. of the shaft, the axis of the hole at MMC must lie within acylindrical tolerance zone equivalent to the diameter of the specified position tolerance. The cylindrical tolerance zonemust be centered on and perpendicular to the axis of the shaft. As the diameter of the hole departs from MMC toward itsLMC, the diameter of the tolerance zone will increase accordingly. Additionally, the axis of the hole must lie totally withinthe locating dimension tolerance.

Keyways, tabs, spline teeth, sprocket teeth, etc.

Where a tab, keyway, sprocket, or spline tooth, etc., are position toleranced to other part features, the centerplane of thetoleranced feature at MMC must lie between two parallel planes separated by the position tolerance. The tolerance zonecreated by the two parallel planes must be centered on the perfect location to the MMC of the datum features.

Another way of expressing this requirement is to define theboundary within which the part must lie (as shown below).

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7.1.4 Calculation of position tolerances. This section defines the method of calculating the maximum positiontolerances that can be applied.

7.1.4.1 Mating parts with floating fasteners (clearance hole in each part)

7.1.4.2 Mating parts with fixed fasteners (clearance hole in one, other pinned or drilled and tapped)

Since the fastener is fixed in one part and only one part has clearance holes, the ∅ 0.8 is the total allowable sum of thetolerance zones applied to both parts. The total allowable tolerance need not be divided evenly between the mating parts.It should be divided in the most useful amounts for manufacturing. The position tolerance for these mating parts could be∅ 0.4 and ∅ 0.4, ∅ 0.5 and ∅ 0.3, ∅ 0.6 and ∅ 0.2, etc.

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7.1.4.3 Two or more fixed diameters aligning for a shaft

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8. FREE STATE VARIATION. Free state variation is a term used to describe distortion of a part after removal offorces applied during manufacture. This distortion is principally due to the weight and flexibility of the part and the releaseof internal stresses resulting from fabrication. A part of this kind is referred to as a non-rigid part.

8.1 SPECIFYING CIRCULARITY IN A FREE STATE WITH AVERAGE DIAMETER

In some cases, it may be required that the part meet its tolerance requirements while in the free state. In such situations,the maximum allowable free state variation should be specified with an appropriate feature control frame. Where formcontrol such as circularity is specified for a circular or cylindrical feature, the pertinent diameter is qualified with theabbreviation AVG. An average diameter is the average of several diametrical measurements (usually not less than four)across a circular or cylindrical feature. Illustrations (a) and (b) (simplified by showing only two measurements) give thepermissible diameters in the free state for two extreme conditions of maximum average diameter and minimum averagediameter, respectively.

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8.2 SPECIFYING RESTRAINT FOR NON-RIGID PARTS

In some cases, it may be necessary to simulate the mating part interface in order to verify individual or related feature

tolerance. This is accomplished by restraining the appropriate features such as the datum features shown in the

illustration below. In this illustration, the runout of the ∅ 13901391 must be checked when the part is restrained to datums A and

B. Additionally in the part’s free state, the ∅ 13901391 must be round within a 2.5 tolerance zone. The ∅ 1390

1391 AVG would be

checked as described in paragraph 8.1.