Dimensional Tolerances

TolerancesHow straight is straight enough? How flat is flatenough? How uniform must a wall thickness bein order to be acceptable? These are notabstract questions. Many products must be manufactured to exacting standards. The specified, acceptable range of deviationfrom a given dimension is known as a tolerance.

Tolerances are measurable, so they can be speci-fied and mutually agreed upon by manufacturersand purchasers, by extruders and their customers. Aluminum profiles can be extrudedto very precise special tolerances or to acceptedstandard dimensional tolerances.

The first portion of the following sectionaddresses standard dimensional tolerances. Thelatter portion of this section is an introduction togeometric tolerancing.

Geometric tolerancing has been likened to amodern technical language that enablesdesigners and engineers to communicate theirrequirements to the people who produce thecomponents of an assembly.

When tolerances are met, parts fit together well,perform as intended, and do not require unnecessary machining. The aluminum extrusion process puts the metal where it isneeded and offers the precision necessary tomeet specified tolerances.

Section

8

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UNDERSTANDING TOLERANCES

What Are Tolerances?Ask any engineering student to makea critical measurement, and his firstquestion may be, “Accurate to howmany decimal places?”

He's just recognizing a basic fact ofnature: that dimensions, whethermeasured or produced, are neverabsolutely exact; they are only as precise as we and our equipment canmake them--or need to make them.Every manufacturing process haslimits of accuracy, imposed by tech-nology or economics, which are rou-tinely taken into account in designand production.

Most manufacturers and customersexpect to provide, or receive, prod-ucts whose dimensions are reliablewithin mutually acceptable limits ofdeviation. Those agreed-upon limitsare called tolerances, and at the timeof ordering, a clear consensusregarding those tolerances benefitsboth the extrusion supplier and theuser. It protects the user by ensuringthat the extruded product will besuitable for his use; it protects theextruder from having products reject-ed by a customer with unreasonableexpectations; it's good business forboth of them.

Aluminum Extrusion Manual 88--11

TOLERANCESSTANDARD DIMENSIONALTOLERANCES

Section

88

A

Note 8Note 6

Length

Cross-section/wall thickness

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88--22

Where Are Dimensional TolerancesApplied?The shape of an aluminum profile isdescribed by specifying the dimen-sions of its cross-section on an engi-neering drawing, and by specifyingthe delivered length.

The allowed tolerances are usuallyexpressed in plus-or-minus (decimal)fractions of an inch or percentages ofa dimension, applied to zones wherethe dimensions are to be held withinthese specified limits.

Unless otherwise specified, standardindustry tolerances are applied.Special tolerances may be specified inconsultation with the extruder.

Extrusion tolerances are applied to avariety of physical dimensions.

Section 8 Tolerances

Y

D

D

Straightness

Twist

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88--33Aluminum Extrusion Manual

C

SurfaceRoughness

Corner & FilletRadii

Contour (Curved Surfaces)

End Cut Squareness(Vertical & Transverse

Angularity

Flatness

A

A

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88--44Section 8 Tolerances

Mean

A

AB

B

At any one point

B

B

Wall thickness

A

AB

A

B

B BA

Extruded tube has additional standard tolerances:

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Width and depth

B

B

AA

A

A

A

A

A

A

A

A

A

A

BB

A

A

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Special TolerancesEven tighter dimensional tolerancesthan the Industry Standard can bespecified when necessary. To achievethem, however, requires moreinvolved die corrections, slower extru-sion rates, increased inspections, andsometimes a higher rejection rate.All that special care adds up, ofcourse, to higher costs to the extrud-er and higher prices to the customer.

In rare instances, a desired dimen-sional tolerance may not be possibleto achieve, but an experienced extru-sion supplier may be able to suggest adesign change that solves the prob-lem and still meets the purchaser'seconomic and functional requirements.

The purchaser and the vendor shouldagree on any special tolerancesbefore an order is entered, andshould specify them on the order andengineering drawing.

The published standard tolerancesmay be very easy to achieve, or verydifficult, depending on the profile. It may be practical and economicallydesirable to specify tolerances thatare broader than the standard.

Remember: If no special dimensionaltolerances are specified, standarddimensional tolerances will beapplied.

Standard Dimensional TolerancesThe industry's standard toleranceswere developed by technical commit-tees of The Aluminum Associationand the American National StandardsInstitute, taking into account boththe capabilities of extruders and theneeds of extrusion users.

These Industry Standards are pub-lished in National StandardDimensional Tolerances for AluminumMill Products (ANSI H35.2) andAluminum Standards and Data (ASD).Both publications are updated peri-odically to reflect improvements inextruder capabilities and changes inuser needs.

Standard tolerances are not simple,uniform fractional formulas. They incorporate many different spe-cific numbers or formulas publishedin tables. The various tolerances areestablished to match the variousdegrees of difficulty an extruder facesin controlling different toleranceddimensions. As a result, tolerancesvary with cross-sectional size (as mea-sured by the profile's fit within a cir-cumscribing circle--see Section 6),and even with the location of eachdimension on a complex shape.Alloy composition and temper alsoinfluence certain tolerances, and arereflected in the standard tolerancetables.

Because of all these important con-siderations, tolerancing tables arecomplex. But their significance issimple and important: under stan-dard tolerances, aluminum extru-sions are routinely produced withdimensions accurate within hun-dredths or thousandths of an inch.For most purposes, that's a more-than-ample degree of precision.

The choice isyours: throughstandard toler-ances or specialtolerances,aluminum extru-sions give youthe precision youneed--where youneed it.

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READING A STANDARD TOLERANCE TABLEUnless otherwise specified, aluminumextrusions are produced to industry-standard dimensional tolerances. Toillustrate this important feature ofaluminum extrusions, standard toler-ance tables are reproduced herefrom Aluminum Standards and Data,1997 and the 1997 ANSI H35.2,Standard Dimensional Tolerances forAluminum Mill Products.

Because the two publications andtheir standards are updated fromtime to time, the following table andillustrations should not be used foractually specifying extrusions. Specifications should be based onlyon the latest approved tolerancetables. Buyers and specifiers areencouraged to consult with theirextruders on a case-by-case basis.

Complexity of Standard Tolerance TablesEven a quick glance at the standardtolerance tables reveals that they arevery detailed and are frequently qualified by footnotes and by refer-ences to additional information.

Reading tolerances from these tablesis a somewhat complex matter, evenfor dimensions across simple rectangular shapes.

A purchaser who is not thoroughlyfamiliar with the use of these tablesshould consult the extrusion supplierto determine which standard tolerance can be expected to apply to critical dimensions of any specificdesign.


All critical dimensions should be discussed between the purchaser andextruder to determine the most practical tolerances for each specificapplication.

Estimating Dimensional Tolerances by“Rules of Thumb”Exact extrusion tolerances can bedetermined only by careful applica-tion of standard tolerance tables andconsultation with the extruder.

Often, however, it is not necessary orpractical to determine exact dimen-tional tolerances when rough esti-mates may be adequate for initialproduct planning and design.

The following “Rules of Thumb” offereasy estimates of standard tolerances.However, it is emphasized that these“Rules of Thumb” approximationsprovide only rough estimates.

DimensionCross-sectionor profiledimensions

Cutting lengthPiece partsPress parts

Straightness

Twist

Flatness

Wall thickness

Tolerance± .008 per inchof measureddimension

± .015 inches± .062 inches

.0125 inches xlength infeet

0.5 deg. xlength in feet

0.004 x widthin inches± 10%

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88--88

Step-by-Step Illustration of Standard TolerancingJust to show how the tables are used, astep-by-step example of standard


tolerancing is spelled out on the following pages, applied to the“Model Extrusion” that appearsat the top of Table 8-1

1 These Standard Tolerances are applicable to the average profile(shape); wider tolerances may be required for some profiles (shapes)and closer tolerances may be possible for others.

2 The tolerance applicable to a dimension composed of two or morecomponent dimensions is the sum of the tolerances of the componentdimensions if all of the component dimensions are indicated.

3 When a dimension tolerance is specified other than as an equal bilat-eral tolerance, the value of the standard tolerance is that which appliesto the mean of the maximum and minimum dimensions permissibleunder the tolerance for the dimension under consideration.

4 Where dimensions specified are outside and inside, rather than wallthickness itself, the allowable deviation (eccentricity) given in Column 3applies to mean wall thickness. (Mean will thickness is the average oftwo wall thickness measurements taken at opposite sides of the void).

5 In the case of Class 1 Hollow Profiles the standard wall thickness tol-erance for extruded round tube is applicable. (A Class 1 Hollow Profileis one whose void is round and one inch or more in diameter and whoseweight is equally distributed on opposite sides of two or more equallyspaced axes.)

6 At points less than 0.250 inch from base of leg the tolerances in Col. 2are applicable.

7 Tolerances for extruded profiles in T3510, T4510, T6510, T73510,T76510, and T8510 tempers shall be as agreed upon between purchaserand vendor at the time the contract or order is entered.

8 The following tolerances apply where the space is completely enclosed(hollow profiles): For the width (A), the balance is the value shown in Col. 4for the depth dimension (D). For the depth (D), the tolerance is the valueshown in Col. 4 for the width dimension (A). In no case is the tolerance foreither width or depth less than the metal dimensions (Col. 2) at the corners.Example—Alloy 6061 hollow profile having 1 X 3rectangular outside dimensions; width toleranceis ±0.021 inch and depth tolerance ±.034 inch.(Tolerances at corners, Col. 2, metaldimensions, are ±0.024 inch for the width and±0.012 inch for the depth.) Note that the Col. 4tolerance of 0.021 inch must be adjusted to0.024 inch so that it is not less than the Col. 2tolerance.

9 These tolerances do not apply to space dimensions such asdimensions “X” and “Z” of the example (below), even when “Y” is75 percent or more of “X.” For the tolerance applicable to dimensions “X” and “Z” use Col. 4, 5, 6, 7, 8, or 9, dependent on distance “A.”

10 The wall thickness tolerance for hol-low or semihollow profiles shall be asagreed upon between purchaser and ven-dor at the time the contract or order isentered when the nominal thickness of onewall is three times or greater than that ofthe opposite wall.

t

3t or Greater

t3t or Greater

A

YX

Z

cols. 4-9

col. 2

col. 2

col. 3

col. 2

col. 4

col. 4

Note 8Note 6

Table 8-1 Standard Cross-Sectional Dimension Tolerances (Except for T3510, T4510, T6510, T73510, T76510, and T8510 Tempers) 7

cols. 4-9

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Examples Illustrating Use ofthe Standard Tolerance Table

Closed-Space DimensionsAll dimensions designated “Y” areclassed as “metal dimensions” and tolerances are determined from column 2.

Dimensions designated “X” areclassed as “space dimensions throughan enclosed void” and the tolerancesapplicable are determined from col-umn 4 unless 75 percent of thedimension is metal, in which case column 2 applies.

Open-Space DimensionsTolerances applicable to dimensions“X” are determined as follows:

1. Locate dimension “X” in column 1.

2. Determine which of columns 4through 9 is applicable, dependenton distance “A.”

3. Locate proper tolerance in col-umn 4, 5, 6, 7, 8 or 9 in the same lineas dimension “X.”

Dimensions “Y” are “metal dimen-sions”; tolerances are determinedfrom column 2.

Distances “C” are shown merely toindicate incorrect values for deter-mining which of columns 4 through 9apply.

Y (Col. 2)X (Col. 4)

X (Col. 4)X (Col. 4)

X (Col. 4)Y (Col. 2)

Y (Col. 2)

A

X

X (Col. 4)


X (Col. 4)

AY

Y

C

C

A

YC

Y

A

X

X

X

XA

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Two Special CasesI. Tolerances applicable to dimen-sions “X” are determined as follows:

1. Locate distance “B” in column 1.

2. Determine which of columns 4-9 isapplicable, dependent on distance“A.”

3. Locate proper tolerance in col-umn 4, 5, 6, 7, 8, or 9 in same line asvalue chosen in column 1.

II. Tolerances applicable to dimen-sions “X” are not determined fromthe Standard Tolerance Table;tolerances are determined by standard tolerances applicable toangles “A.”

THE EXAMPLEThis example supposes that the“model extrusion” profile is to beproduced with the nominal dimen-sions specified on the drawing

• A lower horizontal leg 9" long.

• An upper horizontal leg 5.9" long.

• A vertical connecting leg at one end.

• A vertical connecting leg whose inner surface is located 2.4 inches from the inside of the end leg.

• A uniform outside depth of 2"

• A uniform metal thickness of 0.200"

• The alloy is assumed to be one of the many choices included on the tolerance table as “Other Alloys.”

Because this profile seems simple--consisting only of parallel surfaces,right angles, and uniform thickness-es--it shows all the more clearly howcommercial standard tolerances canvary from point to point over “open”and “closed” sections.


The standard tolerancing for this profile might beworked out, step-by-step, this way:

A A

X

X

X X

A

A

X

BB

0.200" (H)0.200" (G)(TYP.)

2.000" 2.000" 2.000" 2.000" 2.000"

1.60

0"(K

)

2.000" (M)

(F) (E) (D) (C) (A)(B)

H

5.900"(L)

9.000"(I)2.400" (J)

2.00

0"

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All this step requires is to measure orcalculate the diameter of the profile's“circumscribing circle”--the smallestcircle that completely encloses it.

A circumscribing circle gauge is represented in Section 6.

For this profile, it's clear that the cir-cumscribing circle diameter matchesthe profile's longest point-to-pointdistance, the 9.219-inch diagonalfrom the end of the long leg to theopposite corner of the rectangularhollow.

Since the diameter--9.219 inches--isless than 10 inches, all of the toler-ances for this profile will be found inthe upper part of the table, headed:“Circumscribing Circle Sizes LessThan 10 Inches In Diameter.”

Step 1:Determine the Profile Size

Purpose: Figure out which half of thetolerance table assigns tolerances forthe model extrusion's profile.

Method: This part is easy. Profilesthat fit within a “circumscribing circle” less than ten inches in diameter are toleranced by the upperpart of the table. Larger profiles aretoleranced by the lower part.

9.219"

9"

2"

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In the model profile, the 9-inch length of the long leg from end to end(“I”) has no gaps, so it's a metal dimension. So are the 5.9-inch lengthof the shorter leg “L”, the 2-inch lengths along the end leg “A” and mid-leg “M”, and the wall thicknesses themselves as at “G” and “H”.

5.900"

0.200"0.200"

2.000" 2.000"G

H

M A

L

I

.200"

.200"

F

2.000"

In the model profile, the metal thickness is a uniform 0.200 inch. A measurement across the profile through its open (left) side at F includestwo thicknesses of metal through the long and short legs, at 0.200 incheach, for a total of 0.400 inch of metal. This dimension, then, is only 20percent metal (0.400 inch out of a total length of 2 inches). It is obviouslynot a metal dimension. It is, instead, a space dimension.

The user is now ready to refer to the tolerance table inproceeding with the next steps.

Step 2:Identify Metal Dimensions

Purpose: Identify each profile dimen-sion whose length includes at least 75percent metal, versus open space.

Method:a) Scan the profile for dimensionsthat have no gaps in their entirelength. Since these dimensions are100 percent metal and no openspace, they qualify as metal dimensions.

b) Calculate the metal percentage ofany dimension with one or more gapswhich might include at least 75 per-cent metal, to rule it in or out of thiscategory.

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Step 3:Determine Applicability of the MoreGenerous Tolerance on Walls ThatEnclose a Space

Purpose: To assign each metal dimen-sion to its appropriate column on thestandard tolerance table.

Method: There are two columns (Col. 2 and Col. 3) under the generalheading “Metal Dimensions.”The characteristic performance ofextrusion dies that contain hollowspaces dictates this special category.The dies create these voids by sus-pending a mandrel in the metal flow.Should the mandrel move (as italways does to some degree) aneccentricity develops: one wallbecomes slightly thicker and theopposite wall becomes slightly thinnersince both wall thicknesses are deter-mined by the position of the mandrel.

Thus, any wall segment that is part ofa space enclosure is subject to thiseffect when a part of the die, themandrel, shifts; and that wall thick-ness carries a greater tolerance thanwalls in more stable areas of the die.

Column 3 provides the definition that separates them: “Wall ThicknessCompletely Enclosing Space 0.11 sq. in. and Over (Eccentricity).”

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Step 5:Find the Wall Thickness Tolerancefor Metal That Encloses a Space

Purpose: Define special tolerancesfor the walls around the die mandrel(s).

Method: As determined above, toler-ances for closed metal dimensionsare listed in Column 3: “WallThickness Completely EnclosingSpace 0.11 sq. in. and Over(Eccentricity).”

a) For each dimension that meetsthis criterion, read down Column 1to its specified dimension line; then read across to the appropriate alloysubcolumn under Column 3.

b) Tolerances in Column 3 are givenas percentages of the specifieddimension, within fixed limits.Calculate the appropriate percentageto find the tolerance. If the calculat-ed tolerance is larger or smaller thanthe limits provided, the appropriatelimit becomes the tolerance.

Dimension “H” (and all shaded walls), for example, is a 0.200-inch metaldimension, its inner surface completing the enclosure of a rectangularspace 1.600 by 2.400 inches, or 3.84 square inches (greater than 0.11square inch).

To find its standard tolerance, read down Column 1 to the dimension line“0.125-0.249,” then across the Column 3 “Other Alloys,” where the toler-ance is listed as ten percent, but no greater than 0.060 inch and no small-er than 0.010 inch.

The standard tolerance of dimension “H” is ten percent of 0.200 inch,which equals ±0.020 inch and is within the allowed range.

2.400"

1.600"0.200" (H)

Step 4:Select the Appropriate AlloySubcolumn

Purpose: To select the single subcolumn that provides the tolerance for each metal dimension.

Method: There are two subcolumnseach, under Columns 2 and 3, identifying two different groups ofextrusion alloys:• “Alloys 5083, 5086, 5454” on the

left, highlighted (pg. 8-13)• “Other Alloys” on the right.

To make this selection all you need to know is the alloy tobe used for the extrusion.

In the model example presented here, it is assumed thatthe extrusion is to be made of one of the “Other Alloys,”so all of its tolerances will be found in one or another ofthe subcolumns under that caption.

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Step 6:Find the Tolerances for All OtherMetal Dimensions

Purpose: Apply the decisions reachedin the previous steps to read the tableand find the standard tolerances foreach metal dimension.

Method:a) For each metal dimension, readdown Column 1 “SpecifiedDimension” to the appropriate line.

b) Read across that line to the appro-priate alloys-subcolumn of Column 2,where the tolerance is specified.

For example, dimension “A” is specified at 2.000 inches. It has beenidentified, above, as a metal dimension made of an “other alloy.”

To determine its standard tolerance, read down Column 1, “SpecifiedDimension” to line “2.000-3.999”; then read across to Column 2 “OtherAlloys.” The standard tolerance is listed there as “0.024”--twenty-fourthousandths of an inch. (Remember, in this example, to stay in the upperpart of the table, reserved for profiles with a circumscribing circle under10 inches diameter.)

Therefore, dimension “A” would be produced, within standard tolerance,at 2.000 inches ±0.024 inches.

Dimension “G”, although it looks different meets the same conditions as“A”: it is a metal dimension of a wall which does not enclose a space. So its tolerance is found in the same column, but on a different line. Its specified dimension of 0.200 inch would be produced ±0.007 inch atstandard tolerance.

L

G M A

I

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Step 7:Identify the Space Dimensions

Purpose: To identify space dimen-sions and locate the section of thetolerance table that includes them.

Method: Space dimensions are thosemeasurements that include less than75 percent metal (and so more than25 percent open space).

Their tolerances are found under the general heading of “SpaceDimensions” on the standard tolerance table.

2.000"

0.200" (H)0.200" (G)(TYP.)

2.000" 2.000" 2.000" 2.000" 2.000"

1.60

0"(K

)

2.000" (M)

(F) (E) (D) (C) (A)(B)

H

0.200"

Such dimensions can be measured anywhere across a “space” profile.Positions B, C, D, E, and F on the model profile are examples; but spacedimensions could be measured and toleranced at any other appropriatepositions as well.

At each of these positions on the model, a dimension measured acrossthe profile has a total length of 2 inches, which includes two metal thick-nesses of 0.200 inches each. Thus, only 20 percent of the distance ismetal, and these are all “space dimensions.”

The Example

BCDF E

0.200"

5.900"(L)

9.000"(I)2.400" (J)

2.00

0"

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Examples Illustrating Use ofthe Standard Tolerance Table

Closed-Space DimensionsAll dimensions designated “Y” areclassed as “metal dimensions” and tolerances are determined from column 2.

Dimensions designated “X” areclassed as “space dimensions throughan enclosed void” and the tolerancesapplicable are determined from col-umn 4 unless 75 percent of thedimension is metal, in which case column 2 applies.

Figure 8-14 (four examples)

O S Di i

Y (Col. 2)X (Col. 4)


X (Col. 4)Y (Col. 2)

Y (Col. 2)

X (Col. 4)


X (Col. 4)


Step 8:Distinguish Between Open andEnclosed Space Dimensions

Purpose: To determine which toler-ancing methods apply to variousspace dimensions.

Method: At this point it's necessary toread the fine print that comes withthe standard tolerance table.

The “Space Dimensions” heading of the table and themodel profile which illustrates it are both referenced toFootnotes 6 and 8.

Footnote 8 begins: “The following tolerances apply wherethe space is completely enclosed (hollow profiles) . . .”

• If a dimension crosses a completely enclosed void, it isan enclosed space dimension and its tolerance is indicatedby Footnote 8 of the standard tolerance table. See step 11.

• If the dimension crosses a space which is only partiallyenclosed it is an open spaced dimension and its tolerance is found on the table, somewhere in Columns 4 through 9.See steps 9 and 10.

cols. 4-9

col. 2

col. 2

col. 3

col. 2

col. 4

col. 4

Note 8Note 6

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Step 9:Relate Each Open Space Dimensionto Its Tolerance Column

Purpose: Open space dimensionswith identical cross-sections may havedifferent tolerances, depending onhow far they are located from thebase of the nearest supporting leg. The purpose of this step is to assigneach open space dimension to theappropriate column listing its tolerance.

Method: a) Select (or measure) the distancefrom the base of the nearest supporting leg to the location wherethe open space dimension is to betoleranced.

b) Find the “Space Dimensions” column whose range includes this distance. That column contains theapplicable tolerance.

c) Notice Footnote 6: open spacedimensions located less than 0.250inch from the base of a leg are toler-anced by Column 2, as if they weremetal dimensions.

d) As before, select the appropriatealloy subcolumn.

In this example: Dimension “C” is located 0.250 inch from the base of thesupporting leg “M”, so its tolerance is found in Column 4. (If it is locatedless than 0.250 inch from the base of the leg, use column 2, as indicatedin Note 6.)

Dimension “D” is located one inch from the leg, and is toleranced inColumn 5.

Dimension “E” is located 2 inches from the leg, and falls within Column 6.

Dimension “F” is 3 inches from the leg (and just short of the end of theupper arm): it is toleranced by Column 7.

F E D C

3"

0.250"

2"1"

Note that the “baseof leg” is in here

and not out here

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Step 10:Find the Tolerances of the OpenSpace Dimensions

Purpose: Based on the decisionsreached in the preceding steps, readthe standard tolerance table to findthe tolerance for each open spacedimension.

Method: For each open spacedimension, read down Column 1 tothe appropriate “SpecifiedDimension” line; then read across tothe column corresponding to the distance from the dimension to theleg.

Where the line and column intersect,the tolerance is listed for an openspace dimension of that size at thelocation.

For the open space dimensionsassumed in this model example, thetolerance differences associated withdistance from the leg are now apparent:

Distance from Leg Dimension-Tolerance

Dimension “C” 0.250 inch 2.000 ±0.034 inch

Dimension “D” One inch 2.000 ±0.038 inch

Dimension “E” Two inches 2.000 ±0.048 inch

Dimension “F” Three inches 2.000 ±0.057 inch

F E D C

Specified2.000"

±.057"

±.048" ±.038" ±.034"

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Step 11:Determine the Tolerances of theEnclosed Space Dimensions

Purpose: To determine tolerancesfor enclosed space dimensions by fol-lowing the instructions in Footnote 8and in the Enclosed SpaceDimensions example.

Method: When less than 75 percentof a space dimension is metal, theapplicable tolerance is in Column 4 . . . for 75 percent and more, useColumn 2.

Because the rectangular shape is such a common profilein the extrusion industry, specific rules (Footnote 8)apply. For those other, less clear, profiles use this manualas a guide, and then decide the matter of applicable andappropriate tolerances with your extrusion source beforeyou buy.

The example shape is shown below with tolerances indicated for two dimensioning techniques. Follow therules in Footnote 8.

Outside Dimensions

Inside Dimensions

B = 2.000± .034"

1.600± .034"

2.400± .024"

2.800± .034"

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If the practice of using the longdimension to arrive at the tolerancefor the short dimension is not clear,consider this: the longer wall of a rec-tangle is the least well supported andis more likely to deviate from itsintended profile than is the shorterand more closely supported adjacentwall. Since the long wall is also thelimit of the short dimension, it there-by imparts its variations to the shortdimension.

ConclusionThe preceding 11-step illustrationcovered only the cross-sectionaldimensioning techniques most oftenemployed. Even so, not every situation is completely explained. The nature of extrusions is so variedthat full standardization of tolerancesis not a practical goal.

The foregoing cross-sectional tolerances and the linear tolerancesto follow are guides. They apply,when specified, in the absence ofspecifically assigned tolerances.Since the extrusion process canaccommodate special situations, theextrusion user is strongly encouragedto discuss tolerance trade-offs withthe manufacturer or supplier. Byallowing extra margin on somedimensions, a few tighter tolerancescan frequently be achieved withoutsignificant cost effect.

Of the important concepts applicable to the understand-ing of these tables, two must be emphasized.

1. Many tables indicate allowances for both unit devia-tions and overall deviations. The purpose of this dualindication is to preclude the occurrence of a large overalldimensional deviation abruptly within a short distance.Unit deviation limits ensure that an allowable overalldeviation will be appropriately dispersed.

2. The tolerances shown in each table of the followinglineal section are additive. That is, in a single extrudedpiece, straightness tolerance is added to twist tolerance, isadded to flatness tolerance, and so on. Twist toleranceshould be reviewed carefully to avoid misunderstanding.

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[5] Tolerances for T3510, T4510, T6510, T73510, T76510, and T8510 tem-pers shall be as agreed upon between purchaser and vendor at the time the contract or order is entered.[6] See ASD, Standards Section (6), for Application of Twist Limits; for additional information, see Aluminum Association publication “UnderstandingAluminum Extrusion Tolerances.”[7] Applies only if the thickness along at least one-third of the total perimeteris 0.094 or less. Otherwise use the tolerance shown for 0.095 and over.[8] Tolerance for “O” temper material is four times the standard tolerancesshown.Excerpted from Aluminum Standards and Data (ASD), 1997, Tables 11.5 and 11.6.


Table 8-2 Length[1]—Wire, Rod, Bar and Profiles (Shapes)

SPECIFIED DIAMETER (WIRE AND ROD):SPECIFIED WIDTH (BAR):CIRCUMSCRIBING CIRCLE DIAMETER[4]

(PROFILES): inches

TOLERANCE—inches plus ALLOWABLE DEVIATION FROM SPECIFIED LENGTH

SPECIFIED LENGTH—feet

Up through 2.999 1/8 1/4 3/8 13.000-7.999 3/16 5/16 7/16 18.000 and over 1/4 3/8 1/4 1

STANDARD TOLERANCES FOR EXTRUDED WIRE, ROD, BAR AND PROFILES

Up through 12

Over 12through 30

Over 30through 50

Over 50

Table 8-3 Straightness[1]—Rod, Bar and Profiles (Shapes)

PRODUCT TEMPER

SPECIFIED DIAMETER (ROD):

SPECIFIED WIDTH (BAR):

CIRCUMSCRIBING CIRCLE

DIAMETER[4] (PROFILES): (inches)

Rod andSquare,HexagonalandOctagonalBar

RectangularBar

Profiles(Shapes)

All except OTX510[2]

TX511[2]

OTX510[2]

TX511[2]

All except OTX510[2]

TX511[2]

OTX510[2]

TX511[2]

All except OTX510[2][5]

TX511[2]

O

TX511[2]

All

0.500 and over0.500 and over0.500 and overUp through 1.499

1.500 and overOver 0.500Over 0.500Over 0.500Up through 1.499

1.500 and over0.500 and over

0.500 and over

..

..

..

..Up through 0.094[7]

0.095 and overAll

0.500 and over0.500 and over0.500 and overUp through 0.094[7]

0.095 and overAll

Up through 0.094[7]

0.095Up through 0.094[7]

0.095 and over

.0125 x Measured length, ft.

















IN TOTAL LENGTH OR IN ANYMEASURED SEGMENT OF ONE

FOOT OR MORE OF TOTALLENGTH

TOLERANCE[3]—inches

SPECIFIEDTHICKNESS

(RECTANGLES): MINIMUM THICKNESS (PROFILES): (inches)

Footnotes for Tables 8-2 through 8-5[1] These Standard Tolerances are applied to the average profile(shape); wider tolerances may be required for some profiles, andcloser tolerances may be possible for others.[2] TX510 and TX511 are general designations for the followingstress-relieved tempers: T3510, T4510, T61510, T6510, T8510,T73510, T76510, and T3511, T4511, T61511, T6511, T8511,T73511, T76511, respectively.[3] When weight of piece on the flat surface minimizes deviation.[4] The circumscribing circle diameter is the diameter of the smallestcircle that will completely enclose the cross-section of the extrudedproduct.

DD

GUEST


Table 8-4 Twist [1] [6]—Bar and Profiles (Shapes)

PRODUCT TEMPER

SPECIFIED WIDTH (BAR):

CIRCUMSCRIBING CIRCLE

DIAMETER[4]

(PROFILES): (inches)

All except O Up through 1.499 All 1 x Measured length, ft. 7TX510[2] 1.500-2.999 All 1/2 x Measured length, ft. 5TX511[2] 3.000 and over All 1/4 x Measured length, ft. 3O 0.500-1.499 0.500 and over 3 x Measured length, ft. 21

1.500-2.999 0.500 and over 11/2 x Measured length, ft. 153.000 and over 0.500 and over 3/4 Measured length, ft. 9

Bar TX510[2] 0.500-2.999 0.500 and over 1 1/2 x Measured length, ft. 73.000 and over 0.500 and over 1/2 x Measured length, ft. 5

TX511[2] 0.500-1.499 0.500 and over 1 x Measured length, ft. 71.500-2.999 0.500 and over 1/2 x Measured length, ft. 53.000 and over 0.500 and over 1/4 x Measured length, ft. 3

All except O Up through 1.499 All 1 x Measured length, ft. 7TX510[2] [5] 1.500-2.999 All 1/2 x Measured length, ft. 5TX511[2] 3.000 and over All 1/4 x Measured length, ft. 3O 0.500 and over Up through 0.094 [7] 3 x Measured length, ft. 21

0.500-1.499 0.095 and over 3 x Measured length, ft. 21Profiles 1.500-2.999 0.095 and over 11/2 X Measured length, ft. 15(Shapes) 3.000 and over 0.095 and over 3/4 x Measured length, ft. 9

TX511[2] 0.500 and over Up through 0.094[7] 1 x Measured length, ft. 70.500-1.499 0.095 and over 1 x Measured length, ft. 71.500-2.999 0.095 and over 1/2 x Measured length, ft. 53.000 and over 0.095 and over 1/4 x Measured length, ft. 3

IN TOTAL LENGTH OR IN ANYMEASURED SEGMENT OFONE FOOT OR MORE OF

TOTAL LENGTH

MAXIMUM FOR TOTAL

LENGTH

TOLERANCE[3]—degrees

SPECIFIEDTHICKNESS

(RECTANGLES):

MINIMUM THICKNESS (PROFILES):

(inches)

TOLERANCEUp through .0124 .004 .006 .010 .014 .. .. .. .. .. .. ..

0.125-0.187 .004 .006 .008 .012 .014 .014 .014 .. .. .. ..0.188-0.249 .004 .006 .008 .010 .012 .012 .012 .014 .014 .. ..0.250-0.374 .004 .006 .006 .008 .010 .010 .012 .012 .012 .014 ..0.375-0.499 .004 .004 .006 .008 .008 .008 .010 .010 .010 .012 .0140.500-0.749 .004 .004 .006 .006 .008 .008 .008 .008 .010 .010 .0120.750-0.999 .004 .004 .006 .006 .008 .008 .008 .008 .008 .008 .0101.000-1.499 .004 .004 .004 .006 .006 .008 .008 .008 .008 .008 .0081.500-1.999 .004 .004 .004 .004 .006 .006 .006 .008 .008 .008 .008

2.000 and up .004 .004 .004 .004 .004 .006 .006 .006 .008 .008 .008

Excerpted from Aluminum Standards and Data (ASD), 1997, Tables 11.7 and 11.8

Table 8-5 Flatness (Flat Surfaces)[1]—Bar, Solid Profiles & Semihollow Profiles (Shapes)EXCEPT FOR PROFILES IN O[8] T3510, T4510, T6510, T73510, T76510 and T8510 TEMPERS[4]

SURFACE WIDTHS UP THROUGH 1INCH OR ANY 1-INCHINCREMENT OF WIDER SURFACES

Maximum Allowable Deviation D = TOLERANCE (inches)

WIDTHS OVER 1-INCH Maximum Allowable Deviation D = TOLERANCE x W (inches)

MINIMUM THICKNESS OF

METAL FORMINGTHE SURFACE

(inches)

SURFACE WIDTH—inchesUPTO

5.999

6.000TO

7.999

8.000TO

9.999

10.000TO

11.999

12.000TO

13.999

14.000TO

15.999

16.000TO

17.999

18.000TO

19.999

20.000TO

21.999

22.000TO

23.999

24.000ANDUP

Y

W

D

GUEST

Temper

All except O, Allowable deviation from TX510[4] specified contour: 0.005 inch per

inch of chord length; 0.005 inch minimum. Not applicable to contours with chord length6 inches and over.

O Allowable deviation from specified contour: 0.015 inch perinch of chord length; 0.015 inch minimum. Not applicable to contours with chord length 6 inches and over.


TOLERANCEUp through 0.124 .006 .008 .012 .016 .. .. .. .. .. .. ..

0.125-0.187 .006 .008 .010 .014 .016 .. .. .. .. .. ..0.188-0.249 .004 .006 .010 .012 .014 .014 .014 .016 .. .. ..0.250-0.374 .004 .006 .008 .010 .012 .012 .012 .014 .014 .016 ..0.375-0.499 .004 .006 .008 .010 .010 .010 .012 .012 .012 .014 .0160.500-0.749 .004 .004 .006 .008 .008 .008 .010 .010 .012 .012 .0140.750-0.999 .004 .004 .006 .006 .008 .008 .008 .008 .010 .010 .012

1.000 and up .004 .004 .004 .006 .006 .008 .008 .008 .008 .008 .008

Table 8-6 Flatness (Flat Surfaces)[1] HOLLOW PROFILES (SHAPES) EXCEPT FOR PROFILES IN O[10], T3510, T4510, T6510, T73510, T76510 and T8510 TEMPERS[4]

SURFACE WIDTHS UP THROUGH 1 INCH OR ANY 1-INCHINCREMENT OF WIDER SURFACES

Maximum Allowable Deviation D = TOLERANCE (inches)

WIDTHS OVER 1 INCH Maximum Allowable Deviation D = TOLERANCE x W (inches)

MINIMUM THICKNESS OF

METAL FORMINGTHE SURFACE

(inches)

SURFACE WIDTH—inches UPTO

5.999

6.000TO

7.999

8.000TO

9.999

10.000TO

11.999

12.000TO

13.999

14.000TO

15.999

16.000TO

17.999

18.000TO

19.999

20.000TO

21.999

22.000TO

23.999

24.000ANDUP

Up through 0.063 .00150.064-0.125 .0020.126-0.188 .00250.189-0.250 .0030.251-0.500 .0040.501-and over .008

Table 8-7 Surface Roughness[1]

Wire Rod, Bar & Profiles (Shapes)

Table 8-10 Corner and Fillet Radii[1]—Bar & Profiles (Shapes)

TOLERANCE—inchesALLOWABLE DEVIATIONFROM SPECIFIED RADIUS

Difference between radius A and specified radius

SPECIFIED RADIUS[9]

(inches)

SPECIFIED SECTIONTHICKNESS (inches)

ALLOWABLE DEPTHOF CONDITIONS[2]

(inches, max)

Table 8-8 Contour (Curved Surfaces) [1] [3]

— Profiles (Shapes)

Table 8-9 Squareness of Cut Ends[1]

Allowable deviation from square: 1 degree

Sharp corners +1/640.016-0.187 ±1/640.188 and over ±10%

C

D

D

A

A

GUEST

TOLERANCE Degrees plus and minus

Allowable Deviation From SpecifiedAngle


1 21 1 1/21 1

3 63 4 1/23 3

Footnotes for Tables 8-6 through 8-11[1] These Standard Tolerances are applicable to theaverage profile (shape); wider tolerances may berequired for some profiles, and closer tolerances maybe possible for others.

[2] Conditions include die lines and handling marks.

[3] As measured with a contour gauge whose surface islimited to a maximum subtended angle of 90 degrees.Extruded curved surfaces comprising more than a 90degree subtended angle are checked by sliding thegauge across the surface, thus checking two or more90-degree portions of the surface. Extruded profile surfaces comprising arcs formed by two or more radiirequire the use of a separate contour gauge for eachportion of the surface formed by an individual radius.

[4] Tolerances for T3510, T4510, T6510, T 73510,T76510, and T8510 tempers shall be as agreed uponbetween the purchaser and vendor and at the time thecontract or order is entered.

[5] Angles are measured with protractors or with gauges. As illustrated, a four-point contact system is used, twocontact points being as close to theangle vertex as practical, and theothers near the ends of the respec-tive surfaces forming the angle.Between these points of measure-ment, surface flatness is the controlling tolerance.

[6] When the area between the surface forming an angleis all metal, values in column 2 apply if the larger surface length to metal thickness ratio is 1 or less.

[7] When two legs are involved, the one having the larg-er ratio determines the applicable column.

[8] Not applicable to 2219 alloy extrusions. Most profilesin 2219 alloy will have die lines about twice the depthshown in the table; however, for each profile the supplier should be contacted for the roughness value toapply.

[9] If unspecified, the radius shall be 1/32 inch maximum including tolerances.

[10] Tolerance for “O” temper material is four times thestandard tolerance shown.

Excerpted from Aluminum Standards and Data (ASD), 1997, Tables 11.9, 11.10, 11.11, 11.12, 11.13,and 11.14.

Table 8-11 Angularity [1] [5]

TEMPER

1 and less

Column 2Column 1

Over 1 through 40

Column 3

MINIMUM SPECIFIED LEG

THICKNESS (inches)

All exceptO, TX510[4]

O

Up through 0.1870.188-0.749

0.750 and over

Up through 0.1870.188-0.749

0.750 and over

RATIO: [6] [7] LEG OR SURFACELENGTH TO LEG OR METAL

THICKNESS

COL. 3

COL. 3[6]

COL. 3[7]

COL. 3[7]

COL. 2[6]

COL. 2

GUEST

Numbered footnotes follow Table 8-24. Excerpted from Aluminum Standards and Data(ASD), 1997, Tables 12.2 and 12.3. 88--2266Section 8 Tolerances

STANDARD TOLERANCES FOR EXTRUDED TUBE

0.500 - 0.999 .015 .010 .030 .0201.000 - 1.999 .018 .012 .038 .0252.000 - 3.999 .023 .015 .045 .0304.000 - 5.999 .038 .025 .075 .0506.000 - 7.999 .053 .035 .113 .075

8.000 - 9.999 .068 .045 .150 .10010.000 -11.999 .083 .055 .188 .12512.000 -13.999 .098 .065 .225 .15014.000 -15.999 .113 .075 .263 .17516.000 -17.999 .128 .085 .300 .200

Table 8-12 Diameter—Round TubeEXCEPT FOR T3510, T4510,T6510,T75310, AND T8510 TEMPERS[7]

SPECIFIED DIAMETER [1]

(inches)

ALLOWABLE DEVIATION OF MEAN DIAMETER [3] FROMSPECIFIED DIAMETER (Size)

Difference between 1/2 (AA+BB) and specified diameter Difference between AA or BB and specified diameter

ALLOWABLE DEVIATION OF DIAMETER AT ANY POINTFROM SPECIFIED DIAMETER [4]

TOLERANCE[2]-inches plus and minus

Column 1 Alloys 5083, 5086,5454

Other Alloys [16]Alloys 5083, 5086,5454

Other Alloys [16]

Column 2 Column 3

0.500-0.749 .018 .012 .030 .020 0.750-0.999 .021 .014 .030 .0201.000-1.999 .027 .018 .038 .0252.000-3.999 .038 .025 .053 .0354.000-4.999 .053 .035 .068 .0455.000-5.999 .068 .045 .083 .0556.000-6.999 .083 .055 .098 .0657.000-7.999 .098 .065 .108 .0758.000-8.999 .113 .075 .123 .0859.000-9.999 .128 .085 .143 .095

10.000-10.999 .143 .095 .158 .10511.000-12.999 .158 .105 .173 .115

Table 8-13 Width and Depth—Square, Rectangular, Hexagonal, and Octagonal TubeEXCEPT FOR T3510,T4510, T6510, T73510, AND T8510 TEMPERS [7]

SPECIFIED WIDTH or DEPTH

(inches)

ALLOWABLE DEVIATION OF WIDTH ORDEPTH AT CORNERS FROM SPECIFIEDWIDTH OR DEPTH

Difference between AA and specified width or depth Difference between AA and specified width, depth, or distance across flats

ALLOWABLE DEVIATION OF WIDTH OR DEPTH NOT AT CORNERS FROMSPECIFIED WIDTH OR DEPTH [4]

TOLERANCE[2]-inches plus and minus

Column 1Alloys 5083,5086, 5454

All AlloysOther Alloys [16]Alloys 5083,5086, 5454

Other Alloys [16]

SQUARE, RECTANGULARColumn 2

SQUARE, HEXAGONAL, OCTAGO-NAL

RECTANGULARColumn 4

The tolerance for thewidth is the value in theprevious column for adimension equal to thedepth, and conversely,but in no case is the tolerance less than at thecorners.

Example: The width tol-erance of a 1 X 3 inchalloy 6061 rectangulartube is ± 0.025 inch andthe depth tolerance±0.035 inch.

A B

B A

B

A A

B

A A

A

A

A

A

A A

A A

A

AA

A

GUEST

Under 0.047 .008 .005 .012 .008 .005 0.047-0.061 .009 .006 .014 .009 .0070.062-0.124 .011 .007 .015 .010 .0100.125-0.249 .012 .008 .023 .015 .0150.250-0.374 .017 .011 .030 .020 .0250.375-0.499 .021 .014 .045 .030 .0300.500-0.749 .038 .025 .060 .040 .0400.750-0.999 .053 .035 .075 .050 .0501.000-1.499 .068 .045 .090 .060 .0601.500-2.000 .. .. .105 .070 ..

Numbered footnotes follow Table 8-24.Excerpted from Aluminum Standards and Data (ASD), 1997, Tables 12.4 and 12.5.


Under 0.047 .009 .006 .. .. .. .. .. .. 0.047-0.061 .011 .007 .012 .008 .012 .008 .015 .0100.062-0.077 .012 .008 .012 .008 .014 .009 .018 .0120.078-0.124 .014 .009 .014 .009 .015 .010 .023 .0150.125-0.249 .014 .009 .014 .009 .020 .013 .030 .0200.250-0.374 .017 .011 .017 .011 .024 .016 .038 .0250.375-0.499 .. .. .023 .015 .032 .021 .053 .0350.500-0.749 .. .. .030 .020 .042 .028 .068 .0450.750-0.999 .. .. .. .. .053 .035 .083 .0551.000-1.499 .. .. .. .. .068 .045 .098 .0651.500-2.000 .. .. .. .. .. .. .113 .0752.001-2.499 .. .. .. .. .. .. .128 .0852.500-2.999 .. .. .. .. .. .. .143 .0953.000-3.499 .. .. .. .. .. .. .158 .1053.500-4.000 .. .. .. .. .. .. .173 .115

Table 8-14 Wall Thickness—Round Extruded Tube

TABLE 8-15 Wall Thickness—Other-than-Round Extruded Tube

SPECIFIED WALL

THICKNESS [6]

(inches)

Difference between AA andmean wall thickness

TOLERANCE[1] [2]-inches plus and minus

Column 1Alloys508350865454

OtherAlloys [16]

Alloys508350865454

OtherAlloys [16]

Alloys508350865454

OtherAlloys [16]

OtherAlloys [16]

All AlloysAlloys508350865454

Column 2 Column 3Under 1.250

Column 4 Column 5 Column 6

ALLOWABLE DEVIATION OF MEAN WALL THICKNESS [5] FROM SPECIFIED WALL THICKNESS ALLOWABLE DEVIATION OFWALL THICKNESS AT ANYPOINT FROM MEAN WALLTHICKNESS [5] (Eccentricity)

Difference between 1/2 (AA + BB) and specified wall thickness

1.250-2.999OUTSIDE DIAMETER-INCHES

3.000-4.999 5.000 and over

Plus and minus10% of mean wall

thickness

max ± 0.060 min ± 0.010

± 0.120

SPECIFIED WALL

THICKNESS [6]

(inches)

Difference between AA and mean wall thickness

TOLERANCE[1] [2]-inches plus and minus

Column 1Alloys 50835086 5454

OtherAlloys [16]

Alloys 50835086 5454

OtherAlloys [16]

All AlloysAll AlloysColumn 2 Column 3

Under 5.000Column 4 Column 5

ALLOWABLE DEVIATION OF MEAN WALL THICKNESS[5] FROM SPECIFIEDWALL THICKNESS

ALLOWABLE DEVIATION OF WALL THICKNESS[5]

(Eccentricity)

Difference between 1/2 (AA + BB) and specified wall thickness

5.000 and overCIRCUMSCRIBING CIRCLE DIAMETER[10]-inches

Under 5.000 5.000 and over

Plus and minus10% of mean wall

thickness

max ± 0.060 min ± 0.010

A

A

BB

A

A

AA ABA AB

A

GUEST

All except O, 0.500-1.499 All 1 x Measured length, feet 7TX510, TX511[8] 1.500-2.999 All 1/2 x Measured length, feet 5

3.000 and over All 1/4 x Measured length, feet 3TX510[8] 0.500 and over 0.095 and over [7] [7]

TX511[8] 0.500-1.499 0.095 and over 1 x Measured length, feet 71.500-2.999 0.095 and over 1/2 x Measured length, feet 5

3.000 and over 0.095 and over 1/4 x Measured length, feet 3

COILEDSTRAIGHT


0.500-1.249 1/8 1/4 3/8 1 +5%, -0% ±10% ±15% ±20%1.250-2.999 1/8 1/4 3/8 1 .. .. .. ..3.000-7.999 3/16 5/16 7/16 1 .. .. .. ..8.000 & over 1/4 3/8 1/2 1 .. .. .. ..

TABLE 8-16 Length—Extruded Tube

SPECIFIED OUTSIDE

DIAMETEROR WIDTH

(inches)

TOLERANCE-inches plus excepted as notedALLOWABLE DEVIATION FROM SPECIFIED LENGTH

Up through12

Over 12through

30

Over 30through

50

Over 50

Up through100

Over 100through

250

Over 500Over 250through

500

SPECIFIED LENGTH-feet

TABLE 8-17 Twist [11]—Other-than-Round Tube

TABLE 8-18 Straightness—Tube in Straight Lengths

TEMPER SPECIFIEDWIDTH(inches)

SPECIFIEDTHICKNESS

(inches)

IN TOTAL LENGTH OR INANY SEGMENT OF ONE

FOOT OR MORE OF TOTALLENGTH

MAXIMUMFOR TOTAL

LENGTH

TOLERANCE [9]-Degrees

Y (max.) in degrees

ALLOWABLE DEVIATION FROM STRAIGHT

IN TOTAL LENGTH OR INANY SEGMENT OF ONEFOOT OR MORE OF TOTALLENGTH

TEMPER

TOLERANCE [9] [12] -inchesALLOWABLE DEVIATION(D) FROM STRAIGHT

SPECIFIEDWIDTH(inches)

All except 0.500-5.999 .010 x Measured length, feetO, TX510[8] 6.000 and over .020 x Measured length, feet

TX510[8] 0.500 and over [7]

TABLE 8-19 Flatness (Flat Surfaces)Except for 0, T3510, T4510, T6510, T73510, T76510, & T8510 Tempers[7]

WIDTHS UPTHROUGH 1INCHOR ANY 1-INCHINCREMENT OF

WIDERSURFACES

WIDTHS OVER 1INCH THROUGH

5.999 INCHES

TOLERANCE-inches

Maximum Allowable Deviation Y

MINIMUMTHICKNESS OFMETAL FORM-

ING THE SURFACE

(inches)

Up through 0.187 0.006 0.006 x W (inches)0.188 and over 0.004 0.004 x W (inches)

L

Y

Y

D

88--2288

GUEST

Footnotes for Tables 8-12 through 8-24

[1] When outside diameter, inside diameter, and wall thickness (ortheir equivalent dimensions in other-than-round tube) are all speci-fied, standard tolerances are applicable to any two of these dimen-sions, but not to all three. When both outside and inside diametersor inside diameter and wall thickness are specified, the toleranceapplicable to the specified or calculated O.D. dimension shall alsoapply to the I.D. dimension.

[2] When a dimension tolerance is specified other than as an equalbilateral tolerance, the value of the standard tolerance is that whichapplied to the mean of the maximum and minimum dimensions per-missible under the tolerance for the dimension under consideration.

[3] Mean diameter is the average of two diameter measurementstaken at right angles to each other at any point along the length.

[4] Not applicable in the annealed (O) temper or if wall thickness isless than 2 1/2 percent of outside diameter of a circle having a circumference equal to the perimeter of the tube.

[5] The mean wall thickness of round tube is the average of two measurements taken opposite each other. The mean wall thicknessof other-than-round tube is the average of two measurements takenopposite each other at approximate center line of tube and perpendicular to the longitudinal axis of the cross-section.

[6] When dimensions specified are outside and inside, rather than wallthickness itself, allowable deviation at any point (eccentricity) appliesto mean wall thickness.

[7] Tolerances for T3510, T4510, T6510, T73510, T76510, and T8510tempers shall be as agreed upon between purchaser and vendor atthe time the contract or order is entered.

[8] Tempers TX510 and TX511 are general designations for the following stress-relieved tempers: T3510, T4510, T6510, T8510,T73510, T76510; and T3511, T4511, T6511, T8511, T73511, T76511,respectively.

[9] When weight of piece on flat surface minimizes deviation.

[10] The circumscribing circle diameter is the diameter of the smallestcircle that will completely enclose the cross-section of the extrudedproduct.

[11] See ASD, Standards Section (6), for Application of Twist limits.

[12] Tolerances not applicable to TX510 or TX511 temper tube havinga wall thickness less than 0.095 inches.

[13] Conditions include die lines, mandrel lines, and handling marks.

[14] For tube over 12.750 inches O.D. the 2xxx and 7xxx series alloysand 5xxx series alloys with nominal magnesium content of 3 percentor more are excluded.

[15] Not applicable to O temper tube.

[16] Limited to those alloys listed in ASD, Table 12.1.

[17] Not applicable to 2219 alloy tube. Most tubes in 2219 alloy willhave die lines about twice the depth shown in the table; however, foreach tube size the supplier should be contacted for the roughnessvalue to apply.

[18] If unspecified, the radius shall be 1/32 inch maximum including tolerances.

Excerpted from Aluminum Standards and Data (ASD), 1997, Tables 12.10, 12.11, 12.12, 12.13, and 12.14.

TOLERANCE-inchesALLOWABLE

DEVIATION FROMSPECIFIED RADIUS

Difference betweenradius A and

specified radius

Up through Up through 0.063 0.002512.750 0.064-0.125 0.003

0.126-0.188 0.00350.189-0.250 0.0040.251-0.500 0.005

0.501 and over 0.00812.751-15.000 Up through 0.500 0.010

0.501 and over 0.01215.001-20.000 Up through 0.500 0.012

0.501 and over 0.01520.001 and over Up through 0.500 0.015

0.501 and over 0.020


TABLE 8-20 Squareness of Cut EndsAllowable deviation from square: 1 degree.

TABLE 8-22 AngularityAllowable deviation from square: ± 2 degrees.

TABLE 8-24 Dents[15]

Depth of dents shall not exceed twice the tolerances specified in Table 8-12 for diameter at any point from specified diameter, except fortube having a wall thickness less than 2 1/2percent of the outside diameter, in which case the following multipliers apply: 2% to 2 1/2% exclusive-2.5 x tolerance (max.)1 1/2% to 2% exclusive-3.0 x tolerance (max.)1% to 1 1/2% exclusive-4.0 x tolerance (max.)

TABLE 8-23 Surface Roughness[14] [17]

TABLE 8-21 Corner and Fillet Radii

SPECIFIEDRADIUS (inches)

Sharp corners +1/640.016-0.187 ±1/64

0.188 and over ±10%

Specified OutsideDiameter (inches)

Specified WallThickness (inches)

Allowable Depthof Conditions [13]

(inches, max.)

A

GUEST


PROPERTIES AND TOLERANCES FOR EXTRUDED COILEDTUBE

ApplicationExtruded round coiled tube is produced by bridge or porthole dieextrusion methods and is intendedfor general purpose applicationssuch as refrigeration units, oil lines,and instrument lines.

Internal CleanlinessThe tube shall be capable of meetingan inside cleanliness requirement ofno more residue than 0.002 g ofresidue per square foot (0.139 x 10-4g per square inch) ofinternal surface when tested inaccordance with the following paragraph. Tube ends are sealed bycrimping or by other suitable meansto maintain cleanliness during shipping and storage.

Test Method - A measured quantity of solvent (125 ml minimum of inhibited 1,1,1 trichloroethane, trichloroethylene or equal) is pumped or aspiratedthrough a test sample of tube into the flask. The testsample shall have a minimum internal area of 375 squareinches, except that no more than 50 feet of length shallbe required. The solvent is then transferred to apreweighed container such as a crucible, evaporatingdish, or beaker and completely evaporated on a low-temperature hot plate. After solvent evaporation, thecontainer is dried in a furnace or oven for at least 10 minutes at 212-230°F (100-110°C), cooled in a desiccator,then weighed. A blank determination is made on the measured quantity of solvent, and the gain in weight forthe blank is subtracted from the weight of the residuesample. The corrected weight is then calculated in gramsof residue per internal area of tube.

Note: The quantity of solvent used for the blank run is thesame as that used for the actual examination of the tubesample. The sample is prepared so that there is noinclusion of chips, dust, and so forth, resulting from thesample preparation.

Leak TestThe tube is capable of withstanding an internal air pressure of 250 psi with no evidence of leakage or pressure loss.

FormabilityThe tube ends are capable of being expanded by forcinga steel pin having an included angle of 60 degrees intothem until the outside diameter is increased 40 percent.The expansion shall not cause cracks, ruptures, or otherdefects visible to the unaided eye.

GUEST

GUEST

0.250-0.625 0.004 0.006

1050-H112 0.032-0.050 8.5 14.5 2.5 251100-H112 0.032-0.050 11.0 17.0 3.0 251200-H112 0.032-0.050 10.0 16.0 3.0 251235-H112 0.032-0.050 9.0 15.0 3.0 253003-H112 0.032-0.050 14.0 20.0 5.0 25


TABLE 8-25 Mechanical Property Limits [1] [2] and Tolerances—Extruded Coiled Tube

ALLOY AND TEMPER [3]

SPECIFIED WALLTHICKNESS (inches)

ELONGATION percent min. in 2 inches

FULL-SECTION SPECIMEN

TENSILE STRENGTH-ksi

ULTIMATE YIELD

min max min.

TABLE 8-26 Outside Diameter

SPECIFIED OUTSIDEDIAMETER (inches)

ALLOWABLE DEVIATION OF MEAN DIAMETER FROM SPECIFIED DIAMETER

ALLOWABLE DEVIATION OF DIAMETER AT ANYPOINT FROM SPECIFIED DIAMETER

TOLERANCE-inches plus and minus

0.032-0.050 0.003 0.004

TABLE 8-27 Wall Thickness

SPECIFIED WALLTHICKNESS (inches)

ALLOWABLE DEVIATION OF MEAN WALLTHICKNESS FROM SPECIFIED WALL

THICKNESS

ALLOWABLE DEVIATION OF WALL THICKNESSAT ANY POINT FROM SPECIFIED WALL

THICKNESS

TOLERANCE-inches plus and minus

70 min. 80 to 120 percent of nominal30 max. 60 to 80 percent of nominal

TABLE 8-28 Coil Length [4]

PERCENT OF COILS IN SHIPMENT RANGE OF LENGTH

1. The data base and criteria upon which these mechanical property limits are established are outlined in The Aluminum Association publication Aluminum Standards and Data (ASD), 1997, page 6-1, under “Mechanical Properties.”

2. Processes such as flattening, leveling, or straightening coiled products subsequent to shipment by the producer may alter the mechanical properties ofthe metal. (Refer to ASD 1997, Section 4, “Certification Documentation.”)

3. Also available in F (as-extruded temper), for which no mechanical properties are specified or guaranteed.

4. Coil size shall be as agreed upon between supplier and purchaser.

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TOLERANCESGEOMETRIC TOLERANCING

Section

88

INTRODUCTION TOGEOMETRIC DIMENSIONING ANDTOLERANCING

Taken together, geometric dimension-ing and tolerancing can be used tospecify the geometry or shape of anextrusion on an engineering drawing.It can be described as a modern tech-nical language, which has uniformmeaning to all, and can vastlyimprove communication in the cyclefrom design to manufacture.Terminology, however, varies in mean-ing according to the GeometricStandard being used; this must betaken into account in each case.

Geometric dimensioning and toler-ancing, also referred to in colloquialterms as geometrics, is based uponsound engineering and manufactur-ing principles. It more readily cap-tures the design intent by providingdesigners and drafters better toolswith which to "say what they mean."Hence, the people involved in manu-facturing or production can moreclearly understand the design require-ments. In practice, it becomes quiteevident that the basic "engineering"(in terms of extruding, fixturing,inspecting, etc.) is more logically con-sistent with the design intent whengeometric dimensioning and toler-ancing is used. As one example,functional gauging can be used to facilitate the verification process and,at the same time, protect designintent. Geometric dimensioning andtolerancing is also rapidly becoming a

universal engineering drawing language and technique that companies, industries, and govern-ment are finding essential to theiroperational well-being. Over the past30 years, this subject has matured tobecome an indispensable manage-ment tool; it assists productivity, qual-ity, and economics in producing andmarketing products around theworld.

RATIONALE OF GEOMETRIC DIMENSIONING AND TOLERANCINGGeometric dimensioning and toler-ancing builds upon previously estab-lished drawing practices. It adds,however, a new dimension to drawingskills in defining the part and its fea-tures, beyond the capabilities of theolder methods.

It is sometimes effective to considerthe technical benefits of geometricdimensioning and tolerancing byexamining and analyzing a drawingwithout such techniques used,putting the interpretation of such adrawing to the test of clarity. Havethe requirements of such a part beenadequately stated? Can it be pro-duced with the clearest understand-ing? Geometric dimensioning andtolerancing offers that clarity.

Often an engineer is concernedabout fit and function. With manystandard tolerances this may becomea concern. Geometric tolerancing isstructured to better control parts in afit-and-function relationship.

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A

M

S

L

T

A

STRAIGHTNESS

FLATNESS

ANGULARITY

PERPENDICULARITY

PARALLELISM

CONCENTRICITY

POSITION

CIRCULARITY

PROFILE OF A LINE

PROFILE OF A SURFACE

CYLINDRICITY

DIAMETER

DATUM FEATURE

MAXIMUM MATERIALCONDITION (MMC)

REGARDLESS OF FEATURESIZE (RFS)

LEAST MATERIALCONDITION (LMC)

TANGENT PLANE

M A CB0.020

This feature is to be in:“POSITION”

WITHIN

0.020 TOTAL

WITH RESPECT TO

DATUMS A (PRIMARY)B (SECONDARY)C (TERTIARY)

A CYLINDRICALTOLERANCE OF

when the feature is produced AT MAXIMUM MATERIALCONDITION

THE SYMBOLSEffective implementation of geomet-rics first requires a good grasp of themany different symbols and theirfunctional meaning. The followingsymbols are those that are mostcommonly used within the extrusionindustry.

The current standard, as of this writing, is from the American Societyof Mechanical Engineers (ASME)through the American NationalStandards Institute (ANSI) in publication Y14.5, 1994.

For definitions of basic terms used ingeometric tolerancing, refer to theappendix at the end of this section.

Note: Tolerances used within the following examples are purely illustra-tive and may not reflect the standardtolerances used by the aluminumextrusion industry.

THE FEATURE CONTROLFRAMEThe feature control frame is a rectan-gular box containing the geometriccharacteristics symbol and the form,orientation, profile, runout, or loca-tion tolerance. If necessary, datumreferences and modifiers applicableto the feature of the datums are alsocontained in the frame.

or

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Regardless of Feature SizeThe abbreviation for regardless of feature size is RFS, andthe symbol is S within a circle. Regardless of feature sizeis a condition that is used when the importance of loca-tion and/or shape of a feature is independent of the fea-ture's size and forces anyone checking the part to useopen set-up inspection.

RFS - abbreviation

- symbol


The most critical assembly conditionis when External (Male) features aretheir largest and Internal (Female)features are their smallest

MATERIAL CONDITIONSMaximum Material ConditionThe abbreviation for maximum mate-rial condition is MMC and the sym-bol is the capital letter M with a circlearound it. The maximum materialcondition occurs when a featurecontains the most material allowed bythe size tolerance. It is the conditionthat will cause the feature to weighthe most. MMC is often consideredwhen the designer's concern is assem-bly. The minimum clearance or max-imum interference between matingparts will occur when the part fea-tures are at MMC.

The maximum material condition forexternal features occurs when thesize dimension is at its largest.

The maximum material condition forinternal features occurs when the sizedimension is at its smallest.

MMC - abbreviation

- symbol

Least Material ConditionThe abbreviation for least materialcondition is LMC and the symbol is Lwithin a circle. Least material condi-tion is the opposite of maximummaterial condition. In other words,it is a condition of a feature where itcontains the least amount of material. For external parts, thatoccurs when the overall dimension isat a maximum. It is the maximumsize of an internal feature.

LMC - abbreviation

- symbol

M

L

S

RULE # 1 - “Where only a tolerance of size is specified,the limits of size of an individual feature prescribe theextent to which variations in its geometric form, as well assize, are allowed.”

Rule # 2 - “For all applicable geometric tolerances, RFSapplies with respect to individual tolerance, datum refer-ence, or both, where no modifying symbol is specified.MMC, or LMC, must be specified on the drawing where itis required.”

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��

A

B

C

Simulated datums are what hold theparts in production, inspection, andtheir assembly.

ASME 1994and ISO

ANSI Prior to1994

Theoretically Perfect

Simulated Datum

Measurements Are MadeFrom Simulated Datums

Datum Feature

MatingPart

Either Method Means The Following:

DATUMSA datum is a theoretically exact point,axis, or plane that is derived from thetrue geometric counterpart of a speci-fied datum feature. The datum is theorigin from which the location or ori-entation of part features is established.

Confusion can arise if the drawingdoes not specify how a part is to belocated. This is done by specifyingdatums on the drawing.

A drawing of a ball bearing would notrequire a datum because it is a singlefeature part. If a hole were drilled inthe ball bearing, different measure-ments would result if the tolerance of the part were held to beon the feature of the ball or the hole.Adding a datum designation to one ofthese features and referencing to itwould eliminate any confusion.

The datum feature is defined as theactual feature of a part that is used toestablish the datum. Since it is notpossible to establish a theoreticallyexact datum, datums must be simulated. Typical ways to simulate adatum are to use surface plates, angleplates, gauge pins, collets, machinetool beds, etc. The intent of the stan-dard is to hold or fixture the part withsomething that is as close to the true geometric counterpart as possible. The further the fixture deviates fromthe true geometric counterpart, thegreater the set-up error and, therefore, the less reliable themeasurement.

A-A-

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In this example, the 0.500 dimension established two parallel lines. One pair is 0.520 apart (the high limit)and the other pair is 0.480 apart (the low limit). The0.480 can float within the 0.520. If the lower surface wasperfectly flat (right--hand figure), the upper surfacecould be anywhere within a 0.040 tolerance zone.

In this extreme case, it can be said that the top surfacemust be flat within 0.040.


The datums can be thought of as anavigation system for dimensions ofthe part. They might also be thoughtof as a "trap" for the part. On thelower drawing on the opposite page,the datum, in this case datum A,refers to a theoretically perfect datumplane. A surface plate in an inspec-tion area would serve as a simulateddatum and would make contact onthe high points or extremities of thesurface.

These high points are the samepoints that will make contact with themating part in the final assembly.Measurements made from the surfaceplate to other features on the partwill be the best method to predictwhether the part will perform itsintended function.

TOLERANCES OF FORM(Unrelated)

The geometric form of a feature iscontrolled first by a size dimension.Prior to the use of geometric dimensioning and tolerancing, sizedimension was the primary control ofform and did not prove to be sufficient. In some cases, it is toorestrictive and in others, the meaningis unclear. Rule Number 1 (see page8-35) clearly states the degree towhich size controls form.

If the part is manufactured at MMC, both surfaces wouldhave to be perfectly flat.

0.500±0.020

0.520 0.480

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FLATNESSFlatness is the condition of a surfacehaving all elements in one plane.

Flatness usually applies to a surfacebeing used as a primary datum feature.

Other tolerances that provide flatnesscontrol include:

•Any size tolerance on a feature comprised of two internal or externalparallel opposed planes.

•Any flat surface being controlled by:

0.006 A

0.008 A

0.008 A

0.010 A B

0.010 A

0.008 A

One way to improve the form of thesurface is to add a flatness tolerance.This tolerance compares a surface toan ideal or perfectly flat plane. Aflatness tolerance does not locate thesurface.

0.006

0.006

The flatness requirement is placed in a view where thecontrolled surface appears as an edge. The feature control frame may be on either a leader line or an extension line. Since flatness can only be applied to flatsurfaces, it should never be placed next to a size dimension.

Flatness Placement

or

1.000±0.010

Perpendicularity

Parallelism

Angularity

Profile of a Surface

Total Runout

Never a datum reference

, or not allowedM S L

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STRAIGHTNESS (of an axis or center plane)Straightness is a condition underwhich an element of a surface or anaxis is a straight line.

The feature control frame must belocated with the size dimension.

This tolerance is used as a way tooverride the requirement of perfectform at MMC (Rule #1).

Other tolerancing that automaticallyprovides this control are:

The straightness tolerance can beused whenever a straight line ele-ment, axis, or center plane can beidentified on a part. The tolerancezones used for straightness can beeither a pair of parallel lines or acylinder. Each line element, axis, orcenter plane is compared to the tol-erance zone. The tolerance for lineelements is shown on the drawing ina view where the elements to be con-trolled are shown as straight lines.

0.005

0.005

0.005

is implied per Rule # 2(since 1994)

& are allowed

0.470±0.005Front Front

Front

S

M L

Any Size Tolerances ±0.010

Circular Runout

Total Runout

0.006 A

0.010 A

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SURFACE STRAIGHTNESS (on a flatsurface, cylinder, or cone)Other tolerances that provide flatnesscontrol include:

• Any size tolerance on a feature comprised of two internal or external parallel opposed planes.

• Any flat surface being controlled by:

0.008 A

0.008 A

0.010 A B

0.010 A

0.008 A

0.006

0.006

The straightness in this case would be 0.020.

Perpendicularity

Parallelism

Angularity


Total Runout

Flatness

Cylindricity

1.000±0.010

0.004Never a datum reference


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CIRCULARITY (roundness)Circularity is the condition on a surface of revolution (cylinder, cone,sphere) where all points of the surface intersected by any plane (1)perpendicular to a common axis(cylinder, cone) or (2) passingthrough a common center (sphere)are equidistant from the center.

Other tolerances that provide circularity control include:

• Any size tolerance on a cylindricalfeature or sphere.

• Any feature containing circular elements and being controlled by:

Rule of thumb:Runout tolerances are usually lessexpensive to verify and should beconsidered when circularity isdesired.

The tolerance will be on a leaderline, which points to the feature containing the circular element(s).Circularity is similar to straightnessexcept that the tolerance zone isperfectly circular rather than perfectly straight.

Although the circularity tolerancefloats within the limits of size, it isindependent of size and should notbe placed next to the size dimension.


��

��

0.006

0.750±0.005

These two diameters can be of any diameters within the size limits of the feature, provided they remain con-centric and their radial differenceequals the circularity tolerance.

Every circular elementmust be within the tolerance zone.

0.010 A

0.006 A Circular Runout

Total Runout



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CYLINDRICITYCylindricity is a condition of a surfaceof revolution in which all points ofthe surface are equidistant from acommon axis.

Other tolerances that provide thecontrol of cylindricity include:

• Any size tolerance on a cylindrical feature.

• Any feature containing cylindrical features being controlled by:

Rule of thumb:Total runout is usually more costeffective to verify and should be con-sidered when cylindricity is desired.

- No datum reference- Independent of size- May not be modified- Does not locate or orient.

0.010 A

Width of CylindricityTolerance Zone

Total Runout

Tolerance Zone is created bytwo concentric cylinders

0.820±0.005



0.006

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ORIENTATION TOLERANCESOrientation tolerances are applicableto related features, where one featureis selected as a datum feature and theother related to it. Orientation tolerances are perpendicularity, angularity, and parallelism.

Orientation tolerances control theorientation of a feature with respectto a datum that is established by a different part feature (the datum feature).

For that reason, the tolerance willalways include at least one datum reference. Orientation tolerances areconsidered on a “regardless of featuresize” basis unless the maximum material condition modifier is added.The important thing to rememberabout orientation tolerances is that theydo not locate features. Because of that,with the exception of perpendicularityon a secondary datum feature or aplane surface, orientation tolerancesshould not be the only geometric control on a feature. They should,instead, be used as a refinement of atolerance that locates the feature.

A

0.20 A

0.20 A

0.20 A37°

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The perpendicularity of features of size may also be con-trolled. The tolerance will be associated with the sizedimension. When the size dimension applies to a pair ofparallel planes (a slot or tab), the median or center planeis controlled by the tolerance.

A0.20 A


0.008 A 0.008 A

PERPENDICULARITYPerpendicularity is the condition of asurface, axis, or line which is 90degrees from a datum plane or adatum axis.

Perpendicularity is used on a secondary datum feature, relative tothe primary datum.

It may be used to a tertiary datum feature not requiring location.

Other tolerances that may provideperpendicularity include:

0.010 A

0.010 A B

0.020 A B M M

0.020 A B 0.008 A

M M

Position


Total Runout

Therefore, perpendicularityshould usually be used as a

or is permitted

is implied per Rule #2 (since 1994)

Datum reference required(minimum of one)

Could be modified or RFS is implied

M L

The perpendicularity tolerance is specified by beingplaced on an extension line. The tolerance zone isdefined by a pair of parallel planes 0.2 mm apart. Thetolerance zone is perfectly perpendicular to the datumplane -A-. The tolerance zone may be thought of as a flat-ness tolerance zone that is oriented at exactly 90 degreesto the datum.

A

0.20 A

M L

S

50.00±0.06

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PARALLELISMWhen parallelism is applied to a flatsurface, parallelism automaticallyprovides flatness control and is usually easier to measure.

Other tolerances that may provideparallelism include:

Any size tolerance on a feature composed of two internal or externalparallel planes.

Features are considered parallelwhen the distance between themremains constant. Two lines, two surfaces, or a surface and a line maybe parallel. The parallelism of features on a part is controlled bymaking one a datum feature andspecifying a parallelism tolerancewith respect to it.

When parallelism is applied to aplane that is part of a feature of sizeand the other plane of that feature isthe referenced datum feature, theparallelism tolerance cannot begreater than or equal to the total sizetolerance or it would be meaninglesssince the plane's parallelism is auto-matically controlled by the sizedimension.

Parallelism can also be specified onan MMC basis. The MMC modifiercan be on the feature tolerance, thedatum feature, or both. As the fea-ture deviates from its maximummaterial condition, the parallelismtolerance is increased.

0.008 A 0.008 A

0.010 A B

0.020 A B

0.010 A B

M M

A

0.1 A

A

0.1 A0.4 A

M

M

Position


Total Runout

20.0±0.4

12

o4.5±0.1

Required when the featureand the datum feature areboth cylindrical

or is permitted

is implied per Rule #2 (since 1994)


If the primarydatum is a plane

Therefore, parallelism should easily be used as arefinement of Position Profile of a Surface.

M

S

L

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or

is implied perRule #2


ANGULARITYAngularity is the condition of a sur-face, axis, or center plane which is ata specified angle (other than 90degrees) from a datum plane or axis.

Angularity, as a tolerance, alwaysrequires a BASIC angle.

Other tolerances that may provideangular control of features include:

• A tolerance in degrees applied toan angular dimension (not BASIC),provided there is a general note onthe drawing relating toleranceddimensions to a datum referenceframe.

Therefore, angularity should usuallybe used as a refinement of one of theabove:

Angularity is used to control the ori-entation of features to a datum axisor datum plane when they are atsome angle other than 0 or 90degrees. Since angularity does notlocate features, it should only be con-sidered after the feature is located.Usually a locating tolerance such asposition or profile will do an ade-quate job of controlling the angulari-ty and further refinement will not benecessary. A Basic Angle must alwaysbe applied to the feature from thereferenced datum.

0.008 A

0.010 A B

0.020 A B M M

0.008 A 0.020 A B M M

AA

0.20 A

ANGULARITY• Must always have a datum reference• May be modified when controlling a feature of size• Does not locate features• Requires a basic angle.


Position


37°

M L

S

o not allowed

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PROFILEProfile is one of the least used--andyet most useful--geometric tolerancesavailable. There are two types of pro-file tolerance: profile of a line andprofile of a surface. The profile tol-erances are the only geometric toler-ances that may have a datum refer-ence or may not. Without a datumreference in the feature controlframe, the profile tolerance is con-trolling form. Profile of a line is verysimilar to the control seen withstraightness or circularity. Profile ofa surface is similar to the flatness orcylindricity tolerance. Care shouldbe exercised in using profile withouta datum. It usually makes the inspec-tion of the part more difficult.

With a datum reference, the profiletolerance may control form, orienta-tion, and location. Under certainconditions, profile may also controlsize. When a profile tolerance is usedon the drawing, the tolerance isimplied to be centered on the sur-face of the feature that has beendefined by basic dimensions. If it isdesired that the profile toleranceapply only in one direction, this canbe illustrated on the drawing using aphantom line to indicate the side ofthe surface to which the toleranceshould apply. This method of specify-ing the tolerance in only one direc-tion is extremely useful for applica-tions such as a punch and die in tool-ing or a cover on a housing wherethe internal and external featureshave an irregular shape. The basicshape of the object being controlledwith profile must be dimensioned ordefined using basic dimensions.

Profile of a Line


0.020 A

0.020 A

0.020 A

The tolerance zone is implied to becentered on the basic surface unlessshown otherwise on the drawing

Bilateral Tolerance Zone

Unilateral Tolerance Zone(Outside)

Unilateral Tolerance Zone(Inside)

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PROFILE OF A SURFACEProfile of a surface is the conditionpermitting a uniform amount of aprofile variation, either unilaterally orbilaterally, on a surface. (Profile tolerances are the only geometric tolerances where datumreferencing is optional.)

Form, orientation, and location maybe controlled through datum referencing.

If a size dimension is made basic, profile of a surface may also controlsize.

The shape of the feature must bedescribed using basic dimensions.

The best application of profile of asurface is to locate plane and con-toured surfaces.

When irregular parts must fit together, the use of unilateral profiletolerancing makes tolerance analysiseasy for the designer. This approachmay make manufacturing and inspec-tion more difficult since many com-puter numerically controlled (CNC)machine tools and inspectionmachines now use the CAD file,which should usually be created atthe goal or middle values.

0.010 A B

0.004 AWithout a datum reference, profile of a surfacecontrols the form of the surface (similar tostraightness or circularity).

, or

is not permitted

or

is permitted (not recommended)

is implied

M L

S

S

LM

All around symbol

0.008 0.008

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, or

is not permitted

or

is permitted (not recommended)

is implied


PROFILE OF A LINEProfile of a line is the condition permitting a uniform amount of profile variation, either unilaterallyor bilaterally, along a line element ofa feature. (Profile tolerances are theonly geometric tolerances wheredatum referencing is optional.)

Both form and orientation are controlled through datum referencing.

Unless dealing with thin parts, pro-file of a surface is a better choice forlocation.

The shape of the feature must bedescribed using basic dimensions.

Since profile of a surface also con-trols the lines within the surface, pro-file of a line is often used to refineprofile of a surface.

TANGENT PLANETangent plane is a new concept/sym-bol, introduced in the 1994Standard. Normally when a surfaceis inspected for Perpendicularity,Parallelism, Angularity, Profile of aSurface, or Total Runout, the flatnessmust also fall within the aforemen-tioned geometric tolerance or thepart would fail. Tangent Planeexempts the flatness requirement.The gauge block is intended to simulate the mating part.

0.004 0.010 A B

A

0.1 T A

Ignore the out-of-flatcondition when checking parallelism.

Without a datum reference, profile of a line controls the form of linesindependently within a surface (similar to straightness or circularity).

Since profile of a surface also controls the lines within the surface, profile of a line is often used to refine profile of a surface.

Gauge Block

0.010 A B

M L

S

S

LM

20.0±0.4

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CONCENTRICITYConcentricity is a condition in whichtwo or more features (cylinders,cones, spheres, hexagons, etc.) in anycombination have a common axis.

The datum(s) referenced must establish an axis.

Consider circular runout instead ofconcentricity:

• Runout is easier to verify• Runout also controls the form of

the feature.

Concentricity is a static attempt tocontrol dynamic balance.

0.010 A

Required

is implied per Rule #2(since 1994)

& are not allowedM L

S

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APPENDIX to Section 8Basic Terminology for GeometricTolerancing

actual size —- An actual size is the mea-sured size of the feature.

angularity —- Angularity is the conditionof a surface, axis, or center plane, whichis at a specified angle (other than 90degrees) from a datum plane or axis.

basic dimension —- A dimension speci-fied on a drawing as Basic (or abbreviatedBSC) is a theoretical value used todescribe the exact size, shape, or locationof a feature. It is used as the basis fromwhich permissible variations are estab-lished by tolerances on other dimensionsor notes.

basic size —- The basic size is that sizefrom which limits of size are derived bythe application of allowances and toler-ances.

bilateral tolerancing —- A bilateral toler-ance is a tolerance in which variation ispermitted in both directions from thespecified dimension.

center plane —- Center plane is the mid-dle or median plane of a feature.

circular runout —- Circular runout is thecomposite control of circular elements ofa surface independently at any circularmeasuring position as the part is rotatedthrough 360 degrees.

circularity —- Circularity is the conditionon a surface of revolution (cylinder, cone,sphere) where all points of the surfaceintersected by any plane (1) perpendicu-lar to a common axis (cylinder, cone) or(2) passing through a common center(sphere) are equidistant from the center.

clearance fit —- A clearance fit is one having limits of size so prescribed that aclearance always results when matingparts are assembled.

coaxiality —- Coaxiality of features exists when two or more features have coincident axes, i.e., a feature axis and a datumfeature axis.

concentricity —- Concentricity is a condition in which two ormore features (cylinders, cones, spheres, hexagons, etc.) in anycombination have a common axis.

contour tolerancing —- See profile of a line or profile of a surface.

cylindricity —- Cylindricity is a condition of a surface of revolu-tion in which all points of the surface are equidistant from acommon axis.

datum —- A datum is a theoretically exact point, axis, or planederived from the true geometric counterpart of a specifieddatum feature. A datum is the origin from which the location orgeometric characteristics of features of a part are established.

datum axis —- The datum axis is the theoretically exact centerline of the datum cylinder as established by the extremities orcontacting points of the actual datum feature cylindrical surface,or the axis formed at the intersection of two datum planes.

datum feature —- A datum feature is an actual feature of a partwhich is used to establish a datum.

datum feature symbol —- The datum feature symbol containsthe datum reference letter in a rectangular box.

datum line —- A datum line is that which has length but nobreadth or depth such as the intersection line of two planes,center line or axis of holes or cylinders, reference line for func-tional, tooling, or gauging purposes. A datum line is derivedfrom the true geometric counterpart of a specified datum fea-ture when applied in geometric tolerancing.

datum plane —- A datum plane is a theoretically exact planeestablished by the extremities or contacting points of the datumfeature (surface) with a simulated datum plane (surface plate orother checking device). A datum plane is derived from the truegeometric counterpart of a specified datum feature whenapplied in geometric tolerancing.

datum point —- A datum point is that which has position but noextent such as the apex of a pyramid or cone, center point of asphere, or reference point on a surface for functional, tooling,or gauging purposes. A datum point is derived from a specifieddatum target on a part feature when applied in geometric tolerancing.

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datum reference —- A datum reference isa datum feature as specified on a drawing.

datum reference frame —- A datum refer-ence frame is a system of three mutuallyperpendicular datum planes or axesestablished from datum features as a basisfor dimensions for design, manufacture,and verification. It provides completeorientation for the feature involved.

datum surface —- A datum surface or fea-ture (hole, slot, diameter, etc.) refers tothe actual part surface or feature coinci-dental with, relative to, and/or used toestablish a datum.

datum target —- A datum target is a spec-ified datum point, line, or area (identi-fied on the drawing with a datum targetsymbol) used to establish datum points,lines, planes, or areas for special func-tion, or manufacturing and inspectionrepeatability.

dimension —- A dimension is a numericalvalue expressed in appropriate units ofmeasure and indicated on a drawing.

feature —- Feature is the general termapplied to a physical portion of a part,such as a surface, hole, pin, slot, tab, etc.

feature of size —- A feature of size may beone cylindrical or spherical surface, or aset of two plane parallel surfaces, each ofwhich is associated with a dimension; itmay be a feature such as hole, shaft, pin,slot, etc. which has an axis, centerline, orcenterplane when related to geometrictolerances.

feature control frame —- The featurecontrol frame is a rectangular box con-taining the geometric characteristic sym-bol and the form, orientation, profile,runout, or location tolerance. If neces-sary, datum references and modifiersapplicable to the feature of the datumsare also contained in the frame.

fit —- Fit is the general term used to signify the range of tight-ness or looseness which may result from the application of a spe-cific combination of allowances and tolerance on the design ofmating part features. Fits are of four general types: clearance,interference, transition, and line.

flatness —- Flatness is the condition of a surface having all ele-ments in one plane.

form tolerance —- A form tolerance states how far an actual sur-face or feature is permitted to vary from the desired formimplied by the drawing. Expressions of these tolerances refer toflatness, straightness, circularity, and cylindricity.

full indicator movement (FIM) (see also FIR and TIR) —- Fullindicator movement is the total movement observed with thedial indicator (or comparable measuring device) in contact withthe part feature surface during one full revolution of the partabout its datum axis. Full indicator movement (FIM) is the termused internationally. United States terms FIR, and TIR, used inthe past, have the same meaning as FIM.

Full indicator movement also refers to the total indicator move-ment observed while in traverse over a fixed noncircular shape.

full indicator reading (FIR) —- Full indicator reading is the totalindicator movement reading observed with the dial indicator incontact with the part feature surface during one full revolutionof the part about its datum axis. Use of the international term,FIM (which, see), is recommended.

Full indicator reading also refers to the full indicator readingobserved while in traverse over a fixed noncircular shape.

geometric characteristics —- Geometric characteristics refer tothe basic elements or building blocks which form the languageof geometric dimensioning and tolerancing. Generally, the termrefers to all the symbols used in form, orientation, profile,runout, and location tolerancing.

implied datum —- An implied datum is an unspecified datumwhose influence on the application is implied by the dimensional arrangement on the drawing—e.g., the primarydimensions are tied to an edge surface; this edge is implied as adatum surface and plane.

interference fit —- An interference fit is one having limits of sizeso prescribed that an interference always results when matingparts are assembled.

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interrelated datum reference frame —-An interrelated datum reference frame isone which has one or more commondatums with another datum referenceframe.

least material condition (LMC) —- This term implies that condition of a partfeature wherein it contains the least (minimum) amount of material, e.g.,maximum hole diameter and minimumshaft diameter. It is opposite to maxi-mum material condition (MMC).

limits of size —- The limits of size are thespecified maximum and minimum sizesof a feature.

limit dimensions (tolerancing) —- Inlimit dimensioning only the maximumand minimum dimensions are specified.When used with dimension lines, themaximum value is placed above the minimum value, e.g., .300 - .295. Whenused with leader or note on a single line,the minimum limit is placed first, e.g.,.295 - .300.

line fit —- The limits of size are the speci-fied maximum and minimum sizes of afeature.

location tolerance —- A location toler-ance states how far an actual feature mayvary from the perfect location implied by the drawing as related to datums or otherfeatures. Expressions of these tolerancesrefer to the category of geometric charac-teristics containing position and concen-tricity (formerly also symmetry).

maximum material condition (MMC) —-Maximum material condition is that con-dition where a feature of size contains themaximum amount of material within thestated limits of size, e.g., minimum holediameter and maximum shaft diameter. It is opposite to least material condition.

maximum dimension —- A maximum dimension represents theacceptable upper limit. The lower limit may be considered anyvalue less than the maximum specified.

minimum material condition —- See least material condition.

modifier (material condition symbol) —- A modifier is the termsometimes used to describe the application of the “maximummaterial condition,” “regardless of feature size,” or “least material condition” principles. The modifiers are maximummaterial condition (MMC), regardless of feature size (RFS), and least material condition (LMC).

multiple datum reference frames —- Multiple datum referenceframes are more than one datum reference frame on one part.

nominal size —- The nominal size is the stated designationwhich is used for the purpose of general identification, e.g.,1.400, .060, etc.

normality —- See perpendicularity.

orientation tolerance —- Orientation tolerances are applicableto related features, where one feature is selected as a datum feature and the other related to it. Orientation tolerances areperpendicularity, angularity, and parallelism.

parallelepiped —- This refers to the shape of the tolerance zone.The term is used where total width is required and to describegeometrically a square or rectangular prism, or a solid with sixfaces, each of which is a parallelogram.

perpendicularity —- Perpendicularity is the condition of a surface, axis, or line which is 90 degrees from a datum plane or a datum axis.

position tolerance —- A position tolerance (formerly called true position tolerance) defines a zone within which the axis or center plane of a feature is permitted to vary from true (theoretically exact) position.

profile tolerance —- Profile tolerance controls the outline orshape of a part as a total surface or at planes through a part.

profile of line —- Profile of line is the condition permitting auniform amount of profile variation, either unilaterally or bilat-erally, along a line element of a feature.

profile of surface —- Profile of a surface is the condition permit-ting a uniform amount of profile variation, either unilaterally orbilaterally, on a surface.

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projected tolerance zone —- A projectedtolerance zone is a tolerance zoneapplied to a hole in which a pin, stud,screw, or bolt, etc. is to be inserted. Itcontrols the perpendicularity of the holeto the extent of the projection from thehole and as it relates to the mating partclearance. The projected tolerance zoneextends above the surface of the part tothe functional length of the pin, screw,etc., relative to its assembly with the mating part.

regardless of feature size (RFS) —- This isthe condition where the tolerance ofform, runout, or location must be metirrespective of where the feature lies with-in its size tolerance.

roundness —- See circularity.

runout —- Runout is the composite deviation from the desired form of a partsurface of revolution during full rotation(360 degrees) of the part on a datumaxis. Runout tolerance may be circular or total.

runout tolerance —- Runout tolerancestates how far an actual surface or featureis permitted to deviate from the desiredform implied by the drawing during fullrotation of the part on a datum axis.There are two types of runout: circularrunout and total runout.

size tolerance —- A size tolerance stateshow far individual features may vary fromthe desired size. Size tolerances are specified with either unilateral, bilateral,or limit tolerancing methods.

specified datum —- A specified datum is asurface or feature identified with a datumfeature symbol.

squareness —- See perpendicularity.

straightness —- Straightness is a condition where an element ofa surface or an axis is a straight line.

symmetry —- Symmetry is a condition in which a feature (or features) is (are) symmetrically disposed about the center planeof a datum feature.

tolerance —- A tolerance is the total amount by which a specificdimension may vary; thus, the tolerance is the differencebetween limits.

transition fit —- A transition fit is one having limits of size soprescribed that either a clearance or an interference may resultwhen mating parts are assembled.

true position —- True position is a term used to describe theperfect (exact) location of a point, line, or plane of a feature inrelationship with a datum reference or other feature.

total indicator reading (TIR) (see also FIR and FIM) —- Totalindicator reading is the full indicator reading observed with thedial indicator in contact with the part feature surface during onefull revolution of the part about its datum axis. Total indicatorreading also refers to the total indicator reading observed whilein traverse over a fixed noncircular shape. Use of the interna-tional term, FIM (which, see), is recommended.

total runout —- Total runout is the simultaneous composite control of all elements of a surface at all circular and profilemeasuring positions as the part is rotated through 360 degrees.

unilateral tolerance —- A unilateral tolerance is a tolerance inwhich variation is permitted only in one direction from the specified dimension, e.g., 1.400 + .000 - .005.

virtual condition —- Virtual condition of a feature is the collec-tive effect of size, form, and location error that must be consid-ered in determining the fit or clearance between mating parts orfeatures. It is a derived size generated from the profile variationpermitted by the specified tolerances. It represents the mostextreme condition of assembly at MMC.

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Dimensional Tolerances

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