Tolerances Aluminum Extrusions Manual

Section

8

Tolerances How straight is straight enough? How flat is flat enough? How uniform uniform must a wall thickness be in order to be acceptable? acceptable? These are not not abstract questions. questions. Many products products must must be manufactured to exacting standards. standards. The specified, acceptable range of deviation from a given dimension is known as a tolerance. Tolerances are measurable, so they can be specified and mutually agreed upon by manufacturers and purchasers, by extruders and their customers. Aluminum profiles can be extruded to very precise special tolerances or to accepted standard dimensional tolerances. The first portion of the following section addresses standard dimensional tolerances. The latter portion of this section is an introduction to geometric tolerancing. Geometric tolerancing has been likened to a modern technical language that enables designers and engineers to communicate their requirements to the people who produce the components of an assembly. When tolerances are met, parts fit together well, perform as intended, and do not require unnecessary machining. machining. The aluminum extrusion process puts the metal where it is needed and offers the precision necessary to meet specified tolerances.

Section

8

TOLERANCES STANDARD DIMENSIONAL TOLERANCES

UNDERSTANDING TOLERANCES What Are Tolerances? Ask any engineering engineer ing student to make a critical measurement, and his first question may be, “Accurate to how many decimal places?”

He's just recognizing a basic fact of nature: that dimensions, whether measured or produced, are never absolutely exact; they are only as precise as we and our equipment can make them--or need to make them. Every manufacturing process has limits of accuracy, imposed by technology or economics, which are routinely taken into account in design and production. Most manufacturers and customers expect to provide, or receive, products whose dimensions are reliable within mutually acceptable limits of deviation. Those agreed-upon limits are called tolerances, and at the time of ordering, a clear consensus regarding those tolerances benefits both the extrusion supplier and the user. user. It protects the user by ensuring that the extruded product will be suitable for his use; it protects the extruder from having products rejected by a customer with unreasonable expectations; it's good business for both of them.

Note 8 Note 6

Cross-section/wall thickness

A

Length

Aluminum Extrusion Manual

8-11 8-

Section

8

TOLERANCES STANDARD DIMENSIONAL TOLERANCES

UNDERSTANDING TOLERANCES What Are Tolerances? Ask any engineering engineer ing student to make a critical measurement, and his first question may be, “Accurate to how many decimal places?”

He's just recognizing a basic fact of nature: that dimensions, whether measured or produced, are never absolutely exact; they are only as precise as we and our equipment can make them--or need to make them. Every manufacturing process has limits of accuracy, imposed by technology or economics, which are routinely taken into account in design and production. Most manufacturers and customers expect to provide, or receive, products whose dimensions are reliable within mutually acceptable limits of deviation. Those agreed-upon limits are called tolerances, and at the time of ordering, a clear consensus regarding those tolerances benefits both the extrusion supplier and the user. user. It protects the user by ensuring that the extruded product will be suitable for his use; it protects the extruder from having products rejected by a customer with unreasonable expectations; it's good business for both of them.

Note 8 Note 6

Cross-section/wall thickness

A

Length


8-11 8-

Where Are Dimensional Tolerances Tolerances Applied? The shape of an aluminum profile is described by specifying the dimensions of its cross-section on an engineering drawing, and by specifying the delivered length.

Straightness

The allowed tolerances are usually expressed in plus-or-minus (decimal) fractions of an inch or percentages of a dimension, applied to zones where the dimensions are to be held within these specified limits.

D

Unless otherwise specified, standard industry tolerances are applied. Special tolerances may be specified in consultation with the extruder.

D

Extrusion tolerances are applied to a variety of physical dimensions.

Twist

Y Section 8

Tolerances

8-2 82

Surface Roughness

End Cut Squareness (Vertical & Transverse

Contour (Curved Surfaces)

Corner & Fillet Radii

C A A

Angularity Flatness


8-3 83

Extruded tube has additional standard tolerances:

A

B

B

A

B

B

Mean

At any one point

A A

A

A

B

B

B B Wall thickness

Section 8

Tolerances

8-4 84

B A

B

B A

A B

Width and depth

A

A

A

A

A A A

A

A

A

A Aluminum Extrusion Manual

8-5

Standard Dimensional Tolerances The industry's standard tolerances were developed by technical committees of The Aluminum Association and the American National Standards Institute, taking into account both the capabilities of extruders and the needs of extrusion users.

These Industry Standards are published in National Standard Dimensional Tolerances for Aluminum Mill Products (ANSI H35.2) and Aluminum Standards and Data (ASD).

Both publications are updated periodically to reflect improvements in extruder capabilities and changes in user needs. Standard tolerances are not simple, uniform fractional formulas. They incorporate many different specific numbers or formulas published in tables. The various tolerances are established to match the various degrees of difficulty an extruder faces in controlling different toleranced dimensions. As a result, tolerances vary with cross-sectional size (as measured by the profile's fit within a circumscribing circle--see Section 6), and even with the location of each dimension on a complex shape. Alloy composition and temper also influence certain tolerances, and are reflected in the standard tolerance tables.

Special Tolerances Even tighter dimensional tolerances than the Industry Standard can be specified when necessary. To achieve them, however, requires more involved die corrections, slower extrusion rates, increased inspections, and sometimes a higher rejection rate. All that special care adds up, of course, to higher costs to the extruder and higher prices to the customer.

In rare instances, a desired dimensional tolerance may not be possible to achieve, but an experienced extrusion supplier may be able to suggest a design change that solves the problem and still meets the purchaser's economic and functional requirements. The purchaser and the vendor should agree on any special tolerances before an order is entered, and should specify them on the order and engineering drawing. The published standard tolerances may be very easy to achieve, or very difficult, depending on the profile. It may be practical and economically desirable to specify tolerances that are broader than the standard. Remember: If no special dimensional tolerances are specified, standard dimensional tolerances will be applied.

Because of all these important considerations, tolerancing tables are complex. But their significance is simple and important: under standard tolerances, aluminum extrusions are routinely produced with dimensions accurate within hundredths or thousandths of an inch. For most purposes, that's a morethan-ample degree of precision. Section 8

Tolerances

The choice is yours: through standard tolerances or special tolerances, aluminum extrusions give you the precision you need--where you need it.

8-6

Estimating Dimensional Tolerances by “Rules of Thumb” Exact extrusion tolerances can be determined only by careful application of standard tolerance tables and consultation with the extruder.

Often, however, it is not necessary or practical to determine exact dimentional tolerances when rough estimates may be adequate for initial product planning and design. The following “Rules of Thumb” offer easy estimates of standard tolerances. However, it is emphasized that these “Rules of Thumb” approximations provide only rough estimates. Dimension

Tolerance

Cross-section or profile dimensions

± .008 per inch

Cutting length Piece parts Press parts

of measured dimension ± .015 inches ± .062 inches

Straightness

.0125 inches x length in feet

Twist

0.5 deg. x length in feet

Flatness Wall thickness

0.004 x width in inches ± 10%

All critical dimensions should be discussed between the purchaser and extruder to determine the most practical tolerances for each specific application.

READING A STANDARD TOLERANCE TABLE Unless otherwise specified, aluminum extrusions are produced to industrystandard dimensional tolerances. To illustrate this important feature of aluminum extrusions, standard tolerance tables are reproduced here from Aluminum Standards and Data, 1997 and the 1997 ANSI H35.2, Standard Dimensional Tolerances for Aluminum Mill Products.

Because the two publications and their standards are updated from time to time, the following table and illustrations should not be used for actually specifying extrusions. Specifications should be based only on the latest approved tolerance tables. Buyers and specifiers are encouraged to consult with their extruders on a case-by-case basis.

Complexity of Standard Tolerance Tables Even a quick glance at the standard tolerance tables reveals that they are very detailed and are frequently qualified by footnotes and by references to additional information.

Reading tolerances from these tables is a somewhat complex matter, even for dimensions across simple rectangular shapes. A purchaser who is not thoroughly familiar with the use of these tables should consult the extrusion supplier to determine which standard tolerance can be expected to apply to critical dimensions of any specific design.


8-7

Step-by-Step Illustration of Standard Tolerancing Just to show how the tables are used, a step-by-step example of standard tolerancing is spelled out on the following pages, applied to the “Model Extrusion” that appears at the top of Table 8-1

col. 2

col. 4 Note 8 Note 6 cols. 4-9

cols. 4-9

col. 4

col. 3

col. 2 col. 2

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

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 more component dimensions is the sum of the tolerances of the component dimensions if all of the component dimensions are indicated. 3 When a dimension tolerance is specified other than as an equal bilateral tolerance, the value of the standard tolerance is that which applies to the mean of the maximum and minimum dimensions permissible under the tolerance for the dimension under consideration. 4 Where dimensions specified are outside and inside, rather than wall thickness itself, the allowable deviation (eccentricity) given in Column 3 applies to mean wall thickness. (Mean will thickness is the average of two wall thickness measurements taken at opposite sides of the void). 5 In the case of Class 1 Hollow Profiles the standard wall thickness tolerance for extruded round tube is applicable. (A Class 1 Hollow Profile is one whose void is round and one inch or more in diameter and whose weight is equally distributed on opposite sides of two or more equally spaced axes.)

6 At points less than 0.250 inch from base of leg the tolerances in Col. 2 are applicable. 7 Tolerances for extruded profiles in T3510, T4510, T6510, T73510, T76510, and T8510 tempers shall be as agreed upon between purchaser and 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. 4 for the depth dimension (D). For the depth (D), the tolerance is the value shown in Col. 4 for the width dimension (A). In no case is the tolerance for either width or depth less than the metal dimensions (Col. 2) at the corners. Example—Alloy 6061 hollow profile having 1 X 3 rectangular outside dimensions; width tolerance is ±0.021 inch and depth tolerance ±.034 inch. (Tolerances at corners, Col. 2, metal dimensions, are ±0.024 inch for the width and ±0.012 inch for the depth.) Note that the Col. 4 tolerance of 0.021 inch must be adjusted to 0.024 inch so that it is not less than the Col. 2 tolerance.

Section 8

9 These tolerances do not apply to space dimensions such as dimensions “X” and “Z” of the example (below), even when “Y” is 75 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.”

Y

3t or Greater

X Z

t A

t

Tolerances

3t or Greater

10 The wall thickness tolerance for hollow or semihollow profiles shall be as agreed upon between purchaser and vendor at the time the contract or order is entered when the nominal thickness of one wall is three times or greater than that of the opposite wall.

8-8

7

X (Col. 4)

Examples Illustrating Use of the Standard Tolerance Table

Closed-Space Dimensions All dimensions designated “Y” are classed as “metal dimensions” and tolerances are determined from column 2.

X (Col. 4)

X (Col. 4)

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

Dimensions designated “X” are classed as “space dimensions through an enclosed void” and the tolerances applicable are determined from column 4 unless 75 percent of the dimension is metal, in which case column 2 applies.

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

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

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

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

X X

1. Locate dimension “X” in column 1. C

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

A

A

C

Y

Y

3. Locate proper tolerance in column 4, 5, 6, 7, 8 or 9 in the same line as dimension “X.”

A X

Dimensions “Y” are “metal dimensions”; tolerances are determined from column 2.

X

C

A Y

Distances “C” are shown merely to indicate incorrect values for determining which of columns 4 through 9 apply. A

X

Y


8-9

Two Special Cases I. Tolerances applicable to dimensions “X” are determined as follows:

X

1. Locate distance “B” in column 1.

A

A

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

B

3. Locate proper tolerance in column 4, 5, 6, 7, 8, or 9 in same line as value chosen in column 1. II. Tolerances applicable to dimensions “X” are not determined from the Standard Tolerance Table; tolerances are determined by standard tolerances applicable to angles “A.”

X

B

X

A

X

X

A

THE EXAMPLE (F)

This example supposes that the “model extrusion” profile is to be produced with the nominal dimensions specified on the drawing

(E)

(D)

(C)

(B)

(A)

5.900"(L) 2.000" 2.000" 2.000"

2.000" (M)

2.000"

2.000"

"

• A lower horizontal leg 9" long.

0.200" (G)(TYP.)

H

0.200" (H)

• 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.

0 ) 0 K 0 6 . ( 0 0 1 . 2 "

2.400" (J) 9.000"(I)

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

• 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 thicknesses--it shows all the more clearly how commercial standard tolerances can vary from point to point over “open” and “closed” sections. Section 8

Tolerances

8-10

Step 1: Determine the Profile Size

Purpose: Figure out which half of the tolerance table assigns tolerances for the model extrusion's profile. Method: This part is easy. Profiles that fit within a “circumscribing circle” less than ten inches in diameter are toleranced by the upper part of the table. Larger profiles are toleranced by the lower part. 2"

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

"

9

A circumscribing circle gauge is represented in Section 6. For this profile, it's clear that the circumscribing circle diameter matches the profile's longest point-to-point distance, the 9.219-inch diagonal from the end of the long leg to the opposite corner of the rectangular hollow.

"

1 9 9. 2

Since the diameter--9.219 inches--is less than 10 inches, all of the tolerances for this profile will be found in the upper part of the table, headed: “Circumscribing Circle Sizes Less Than 10 Inches In Diameter.”


8-11

Step 2: Identify Metal Dimensions

M

A

5.900"

L

0.200"

H 0.200"

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

I 2.000"

G

Method: a) Scan the profile for dimensions that have no gaps in their entire length. Since these dimensions are 100 percent metal and no open space, they qualify as metal dimensions.

2.000"

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 length of the shorter leg “L”, the 2-inch lengths along the end leg “A” and midleg “M”, and the wall thicknesses themselves as at “G” and “H”.

b) Calculate the metal percentage of any dimension with one or more gaps which might include at least 75 percent metal, to rule it in or out of this category.

.200"

F

2.000"

.200" 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 includes two thicknesses of metal through the long and short legs, at 0.200 inch each, for a total of 0.400 inch of metal. This dimension, then, is only 20 percent metal (0.400 inch out of a total length of 2 inches). It is obviously not a metal dimension. It is, instead, a space dimension.

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

Section 8

Tolerances

8-12

Step 3: Determine Applicability of the More Generous Tolerance on Walls That Enclose a Space

Purpose: To assign each metal dimension to its appropriate column on the standard tolerance table. Method: There are two columns (Col. 2 and Col. 3) under the general heading “Metal Dimensions.” The characteristic performance of extrusion dies that contain hollow spaces dictates this special category. The dies create these voids by suspending a mandrel in the metal flow. Should the mandrel move (as it always does to some degree) an eccentricity develops: one wall becomes slightly thicker and the opposite wall becomes slightly thinner since both wall thicknesses are determined by the position of the mandrel.

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

Thus, any wall segment that is part of a space enclosure is subject to this effect when a part of the die, the mandrel, shifts; and that wall thickness carries a greater tolerance than walls in more stable areas of the die.


8-13

Step 4: Select the Appropriate Alloy Subcolumn

Purpose: To select the single subcolumn that provides the tolerance for each metal dimension. Method: There are two subcolumns each, under Columns 2 and 3, identifying two different groups of extrusion 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 to be used for the extrusion. In the model example presented here, it is assumed that the extrusion is to be made of one of the “Other Alloys,” so all of its tolerances will be found in one or another of the subcolumns under that caption.

Step 5: Find the Wall Thickness Tolerance for Metal That Encloses a Space Purpose: Define special tolerances for the walls around the die mandrel(s). Method: As determined above, tolerances for closed metal dimensions are listed in Column 3: “Wall Thickness Completely Enclosing Space 0.11 sq. in. and Over (Eccentricity).”

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

2.400" 0.200" (H)

1.600"

Dimension “H” (and all shaded walls), for example, is a 0.200-inch metal dimension, its inner surface completing the enclosure of a rectangular space 1.600 by 2.400 inches, or 3.84 square inches (greater than 0.11 square 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 tolerance is listed as ten percent, but no greater than 0.060 inch and no smaller 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.

b) Tolerances in Column 3 are given as percentages of the specified dimension, within fixed limits. Calculate the appropriate percentage to find the tolerance. If the calculated tolerance is larger or smaller than the limits provided, the appropriate limit becomes the tolerance. Section 8

Tolerances

8-14

Step 6: Find the Tolerances for All Other Metal Dimensions

G

M

A

L

Purpose: Apply the decisions reached in the previous steps to read the table and find the standard tolerances for each metal dimension. Method: a) For each metal dimension, read down Column 1 “Specified Dimension” to the appropriate line.

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

I

For example, dimension “A” is specified at 2.000 inches. It has been identified, above, as a metal dimension made of an “other alloy.” To determine its standard tolerance, read down Column 1, “Specified Dimension” to line “2.000-3.999”; then read across to Column 2 “Other Alloys.” The standard tolerance is listed there as “0.024”--twenty-four thousandths of an inch. (Remember, in this example, to stay in the upper part of the table, reserved for profiles with a circumscribing circle under 10 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 at standard tolerance.


8-15

Step 7: Identify the Space Dimensions

The Example (F)

(E)

(D)

(C)

(B)

(A)

5.900"(L)

Purpose: To identify space dimensions and locate the section of the tolerance table that includes them. Method: Space dimensions are those measurements that include less than 75 percent metal (and so more than 25 percent open space).

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

2.000" 2.000" 2.000"

2.000" (M)

2.000"

2.000"

"

0.200" (H)

H

0.200" (G)(TYP.)

0 ) 0 K 0 6 . ( 0 0 1 . 2 "

2.400" (J) 9.000"(I) At each of these positions on the model, a dimension measured across the profile has a total length of 2 inches, which includes two metal thicknesses of 0.200 inches each. Thus, only 20 percent of the distance is metal, and these are all “space dimensions.”

F

E

D

C

B

2.000"

0.200"

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 space dimensions could be measured and toleranced at any other appropriate positions as well.

Section 8

Tolerances

8-16

Step 8: Distinguish Between Open and Enclosed Space Dimensions

The “Space Dimensions” heading of the table and the model profile which illustrates it are both referenced to Footnotes 6 and 8. Footnote 8 begins: “The following tolerances apply where the space is completely enclosed (hollow profiles) . . .”

Purpose: To determine which tolerancing methods apply to various space dimensions. Method: At this point it's necessary to read the fine print that comes with the standard tolerance table.

• If a dimension crosses a completely enclosed void, it is an enclosed space dimension and its tolerance is indicated by Footnote 8 of the standard tolerance table. See step 11. • If the dimension crosses a space which is only partially enclosed 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. col. 4

col. 2

Note 8 Note 6

cols. 4-9

col. 3

col. 4

col. 2 col. 2 X(Col.4)

Examples Illustrating Use of the Standard Tolerance Table

Closed-Space Dimensions All dimensions designated “Y” are classed as “metal dimensions” and tolerances are determined from column 2.

Dimensions designated “X” are classed as “space dimensions through an enclosed void” and the tolerances applicable are determined from column 4 unless 75 percent of the dimension is metal, in which case column 2 applies. Figure 8-14 (four examples)

X(Col.4)

X(Col.4)

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

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

X(Col.4)

Y(Col.2)

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


8-17

3" 2"

Step 9: Relate Each Open Space Dimension to Its Tolerance Column

Purpose: Open space dimensions with identical cross-sections may have different tolerances, depending on how far they are located from the base of the nearest supporting leg. The purpose of this step is to assign each open space dimension to the appropriate column listing its tolerance. Method: a) Select (or measure) the distance from the base of the nearest supporting leg to the location where the open space dimension is to be toleranced.

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

1"

F

E

D

0.250"

C

In this example: Dimension “C” is located 0.250 inch from the base of the supporting leg “M”, so its tolerance is found in Column 4. (If it is located less than 0.250 inch from the base of the leg, use column 2, as indicated in Note 6.) Dimension “D” is located one inch from the leg, and is toleranced in Column 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 the upper arm): it is toleranced by Column 7.

c) Notice Footnote 6: open space dimensions located less than 0.250 inch from the base of a leg are toleranced by Column 2, as if they were metal dimensions. d) As before, select the appropriate alloy subcolumn.

Note that the “base of leg” is in here

and not out here

Section 8

Tolerances

8-18

Step 10: Find the Tolerances of the Open Space Dimensions

±.057"

Purpose: Based on the decisions reached in the preceding steps, read the standard tolerance table to find the tolerance for each open space dimension.

F

Method: For each open space dimension, read down Column 1 to the appropriate “Specified Dimension” line; then read across to the column corresponding to the distance from the dimension to the leg.

Where the line and column intersect, the tolerance is listed for an open space dimension of that size at the location. For the open space dimensions assumed in this model example, the tolerance differences associated with distance from the leg are now apparent:

±.048" ±.038" ±.034"

Specified 2.000"

E

D

C

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


8-19

Step 11: Determine the Tolerances of the Enclosed Space Dimensions

Purpose: To determine tolerances for enclosed space dimensions by following the instructions in Footnote 8 and in the Enclosed Space Dimensions example.

Because the rectangular shape is such a common profile in the extrusion industry, specific rules (Footnote 8) apply. For those other, less clear, profiles use this manual as a guide, and then decide the matter of applicable and appropriate tolerances with your extrusion source before you buy. The example shape is shown below with tolerances indicated for two dimensioning techniques. Follow the rules in Footnote 8.

Method: When less than 75 percent of a space dimension is metal, the applicable tolerance is in Column 4 . . . for 75 percent and more, use Column 2.

B = 2.000± .034"

Outside Dimensions 2.800 ± .034"

1.600± .034"

Inside Dimensions

2.400± .024"

Section 8

Tolerances

8-20

If the practice of using the long dimension to arrive at the tolerance for the short dimension is not clear, consider this: the longer wall of a rectangle is the least well supported and is more likely to deviate from its intended profile than is the shorter and more closely supported adjacent wall. Since the long wall is also the limit of the short dimension, it thereby imparts its variations to the short dimension. Conclusion The preceding 11-step illustration covered only the cross-sectional dimensioning techniques most often employed. Even so, not every situation is completely explained. The nature of extrusions is so varied that full standardization of tolerances is not a practical goal.

The foregoing cross-sectional tolerances and the linear tolerances to follow are guides. They apply, when specified, in the absence of specifically assigned tolerances. Since the extrusion process can accommodate special situations, the extrusion user is strongly encouraged to discuss tolerance trade-offs with the manufacturer or supplier. By allowing extra margin on some dimensions, a few tighter tolerances can frequently be achieved without significant cost effect.

Of the important concepts applicable to the understanding of these tables, two must be emphasized. 1. Many tables indicate allowances for both unit deviations and overall deviations. The purpose of this dual indication is to preclude the occurrence of a large overall dimensional deviation abruptly within a short distance. Unit deviation limits ensure that an allowable overall deviation will be appropriately dispersed. 2. The tolerances shown in each table of the following lineal section are additive. That is, in a single extruded piece, straightness tolerance is added to twist tolerance, is added to flatness tolerance, and so on. Twist tolerance should be reviewed carefully to avoid misunderstanding.


8-21

STANDARD TOLERANCES FOR EXTRUDED WIRE, ROD, BAR AND PROFILES

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 Up through 2.999 3.000-7.999 8.000 and over

TOLERANCE—inches plus ALLOWABLE DEVIATION FROM SPECIFIED LENGTH SPECIFIED LENGTH—feet Up through 12

Over 12 through 30

Over 30 through 50

Over 50

1/8 3/16 1/4

1/4 5/16 3/8

3/8 7/16 1/4

1 1 1

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

PRODUCT

Rod and Square, Hexagonal and Octagonal Bar

Rectangular Bar

Profiles (Shapes)

TEMPER

All except O TX510[2] TX511[2] O TX510[2] TX511[2] All except O TX510[2] TX511[2] O TX510[2] TX511[2] All except O TX510[2][5] TX511[2] O TX511[2]

SPECIFIED DIAMETER (ROD): SPECIFIED WIDTH (BAR): CIRCUMSCRIBING CIRCLE DIAMETER[4] (PROFILES): (inches)

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

All

..

0.500 and over 0.500 and over 0.500 and over Up through 1.499

1.500 and over 0.500 and over 0.500 and over

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, and closer tolerances may be possible for others. [2] TX510 and TX511 are general designations for the following stress-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 smallest circle that will completely enclose the cross-section of the extruded product.

D

IN TOTAL LENGTH OR IN ANY MEASURED SEGMENT OF ONE FOOT OR MORE OF TOTAL LENGTH

.0125 x Measured length, ft.

.. .. .. Up through 0.094[7] 0.095 and over All 0.500 and over 0.500 and over 0.500 and over Up through 0.094[7] 0.095 and over All Up through 0.094[7] 0.095 Up through 0.094[7] 0.095 and over

1.500 and over Over 0.500 Over 0.500 Over 0.500 Up through 1.499

D

.050 x Measured length, ft. .050 x Measured length, ft. .0125 x Measured length, ft. .050 x Measured length, ft. .0125 x Measured length, ft. .0125 x Measured length, ft. .050 x Measured length, ft. .050 x Measured length, ft. .0125 x Measured length, ft. .050 x Measured length, ft. .0125 x Measured length, ft. .0125 x Measured length, ft. .200 x Measured length, ft. .050 x Measured length, ft. .050 x Measured length, ft. .0125 x Measured length, ft.

Tolerances for T3510, T4510, T6510, T73510, T76510, and T8510 tempers 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 “Understanding Aluminum Extrusion Tolerances.” [7] Applies only if the thickness along at least one-third of the total perimeter is 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 tolerances shown. Excerpted from Aluminum Standards and Data (ASD), 1997, Tables 11.5 and 11.6. [5]

Section 8

Tolerances

8-22

Table 8-4 Twist [1] [6]—Bar and Profiles (Shapes) SPECIFIED WIDTH (BAR): PRODUCT

CIRCUMSCRIBING CIRCLE DIAMETER[4] (PROFILES): (inches)

TEMPER

All except O TX510[2] TX511[2] O

Bar

TX510[2] TX511[2]

All except O TX510[2] [5] TX511[2] O Profiles (Shapes) TX511[2]

Up through 1.499 1.500-2.999 3.000 and over 0.500-1.499 1.500-2.999 3.000 and over 0.500-2.999 3.000 and over 0.500-1.499 1.500-2.999 3.000 and over Up through 1.499 1.500-2.999 3.000 and over 0.500 and over 0.500-1.499 1.500-2.999 3.000 and over 0.500 and over 0.500-1.499 1.500-2.999 3.000 and over

TOLERANCE [3]— degrees

SPECIFIED THICKNESS (RECTANGLES):

Y

MINIMUM THICKNESS (PROFILES): (inches)

IN TOTAL LENGTH OR IN ANY MEASURED SEGMENT OF ONE FOOT OR MORE OF TOTAL LENGTH

MAXIMUM FOR TOTAL LENGTH

All 1 x Measured length, ft. All 1/2 x Measured length, ft. All 1/4 x Measured length, ft. 0.500 and over 3 x Measured length, ft. 0.500 and over 11/2 x Measured length, ft. 0.500 and over 3/4 Measured length, ft. 0.500 and over 1 1/2 x Measured length, ft. 0.500 and over 1/2 x Measured length, ft. 0.500 and over 1 x Measured length, ft. 0.500 and over 1/2 x Measured length, ft. 0.500 and over 1/4 x Measured length, ft. All 1 x Measured length, ft. All 1/2 x Measured length, ft. All 1/4 x Measured length, ft. Up through 0.094 [7] 3 x Measured length, ft. 0.095 and over 3 x Measured length, ft. 0.095 and over 11/2 X Measured length, ft. 0.095 and over 3/4 x Measured length, ft. [7] Up through 0.094 1 x Measured length, ft. 0.095 and over 1 x Measured length, ft. 0.095 and over 1/2 x Measured length, ft. 0.095 and over 1/4 x Measured length, ft.

7 5 3 21 15 9 7 5 7 5 3 7 5 3 21 21 15 9 7 7 5 3

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-INCH INCREMENT OF WIDER SURFACES Maximum Allowable Deviation D = TOLERANCE (inches)

D

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

W

MINIMUM THICKNESS OF METAL FORMING THE SURFACE (inches) Up through .0124 0.125-0.187 0.188-0.249 0.250-0.374 0.375-0.499 0.500-0.749 0.750-0.999 1.000-1.499 1.500-1.999 2.000 and up Excerpted from

UP TO 5.999 .004 .004 .004 .004 .004 .004 .004 .004 .004 .004

6.000 TO 7.999 .006 .006 .006 .006 .004 .004 .004 .004 .004 .004

8.000 TO 9.999 .010 .008 .008 .006 .006 .006 .006 .004 .004 .004

SURFACE WIDTH—inches 10.000 12.000 14.000 16.000 18.000 20.000 22.000 24.000 TO TO TO TO TO TO TO AND 11.999 13.999 15.999 17.999 19.999 21.999 23.999 UP TOLERANCE .014 .. .012 .014 .010 .012 .008 .010 .008 .008 .006 .008 .006 .008 .006 .006 .004 .006 .004 .004

Aluminum Standards and Data (ASD),

.. .014 .012 .010 .008 .008 .008 .008 .006 .006

.. .014 .012 .012 .010 .008 .008 .008 .006 .006

.. .. .014 .012 .010 .008 .008 .008 .008 .006

1997, Tables 11.7 and 11.8


.. .. .014 .012 .010 .010 .008 .008 .008 .008

.. .. .. .014 .012 .010 .008 .008 .008 .008

.. .. .. .. .014 .012 .010 .008 .008 .008

8-23

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-INCH INCREMENT OF WIDER SURFACES Maximum Allowable Deviation D = TOLERANCE (inches)

D

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

D

MINIMUM THICKNESS OF METAL FORMING THE SURFACE (inches)

UP TO 5.999

Up through 0.124 0.125-0.187 0.188-0.249 0.250-0.374 0.375-0.499 0.500-0.749 0.750-0.999 1.000 and up

.006 .006 .004 .004 .004 .004 .004 .004

6.000 TO 7.999 .008 .008 .006 .006 .006 .004 .004 .004

8.000 TO 9.999

SURFACE WIDTH—inches 10.000 12.000 14.000 16.000 18.000 20.000 22.000 24.000 TO TO TO TO TO TO TO AND 11.999 13.999 15.999 17.999 19.999 21.999 23.999 UP

.012 .010 .010 .008 .008 .006 .006 .004

.. .. .014 .012 .010 .008 .008 .008

.. .. .014 .012 .012 .010 .008 .008

.. .. .016 .014 .012 .010 .008 .008

.. .. .. .014 .012 .012 .010 .008

.. .. .. .016 .014 .012 .010 .008

.. .. .. .. .016 .014 .012 .008

Table 8-9 Squareness of Cut Ends[1]

Table 8-7 Surface Roughness[1] Wire Rod, Bar & Profiles (Shapes)

Allowable deviation from square: 1 degree

SPECIFIED SECTION ALLOWABLE DEPTH OF CONDITIONS[2] THICKNESS (inches) (inches, max) Up through 0.063 0.064-0.125 0.126-0.188 0.189-0.250 0.251-0.500 0.501-and over

TOLERANCE .016 .. .014 .016 .012 .014 .010 .012 .010 .010 .008 .008 .006 .008 .006 .006

.0015 .002 .0025 .003 .004 .008

Table 8-10 Corner and Fillet Radii[1]— Bar & Profiles (Shapes) TOLERANCE—inches ALLOWABLE DEVIATION FROM SPECIFIED RADIUS SPECIFIED RADIUS[9] (inches) A

Table 8-8 Contour (Curved Surfaces)

[1] [3]

A

— Profiles (Shapes)

Difference between radius A and specified radius

C

Temper

Sharp corners 0.016-0.187 0.188 and over

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

Section 8

Tolerances

+1/64 ±1/64 ±10%

8-24

Footnotes for Tables 8-6 through 8-11 [1] These Standard Tolerances are applicable to the average profile (shape); wider tolerances may be required for some profiles, and closer tolerances may be possible for others. [2]

Table 8-11 Angularity [1] [5] TOLERANCE Degrees plus and minus Allowable Deviation From Specified COL. 3 Angle

Conditions include die lines and handling marks.

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

TEMPER

MINIMUM SPECIFIED LEG THICKNESS (inches)

COL. 3[7]

COL. 2

RATIO: LEG OR SURFACE LENGTH TO LEG OR METAL THICKNESS [6] [7]

Tolerances for T3510, T4510, T6510, T 73510, T76510, and T8510 tempers shall be as agreed upon between the purchaser and vendor and at the time the contract or order is entered. Angles are measured with protractors or with gauges. As illustrated, a four-point contact system is used, two contact points being as close to the angle vertex as practical, and the others near the ends of the respective surfaces forming the angle. Between these points of measurement, surface flatness is the controlling tolerance.

COL. 2[6]

COL. 3[7]

[4]

[5]

COL. 3[6]

All except O, TX510[4]

O

1 and less

Over 1 through 40

Column 1

Column 2

Column 3

Up through 0.187 0.188-0.749 0.750 and over

1 1 1

2 1 1/2 1

Up through 0.187 0.188-0.749 0.750 and over

3 3 3

6 4 1/2 3

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

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

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

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

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

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


8-25

STANDARD TOLERANCES FOR EXTRUDED TUBE

Table 8-12 Diameter—Round Tube EXCEPT FOR T3510, T4510,T6510,T75310, AND T8510 TEMPERS[7] TOLERANCE[2]-inches plus and minus ALLOWABLE DEVIATION OF MEAN DIAMETER SPECIFIED DIAMETER (Size)

SPECIFIED DIAMETER [1] (inches)

[3]

FROM

ALLOWABLE DEVIATION OF DIAMETER AT ANY POINT FROM SPECIFIED DIAMETER [4]

B A

B A

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

Column 1 0.500 1.000 2.000 4.000 6.000 -

0.999 1.999 3.999 5.999 7.999

8.000 - 9.999 10.000 -11.999 12.000 -13.999 14.000 -15.999 16.000 -17.999

Column 2 Other Alloys Alloys 5083, 5086, 5454 .015 .010 .018 .012 .023 .015 .038 .025 .053 .035 .068 .083 .098 .113 .128

B Difference between AA or BB and specified diameter

Column 3 Other Alloys Alloys 5083, 5086, 5454 .030 .020 .038 .025 .045 .030 .075 .050 .113 .075

[16]

.045 .055 .065 .075 .085

.150 .188 .225 .263 .300

[16]

.100 .125 .150 .175 .200

Table 8-13 Width and Depth—Square, Rectangular, Hexagonal, and Octagonal Tube EXCEPT FOR T3510,T4510, T6510, T73510, AND T8510 TEMPERS [7] TOLERANCE[2]-inches plus and minus ALLOWABLE DEVIATION OF WIDTH OR DEPTH NOT AT CORNERS FROM SPECIFIED WIDTH OR DEPTH [4]

ALLOWABLE DEVIATION OF WIDTH OR DEPTH AT CORNERS FROM SPECIFIED WIDTH OR DEPTH A

SPECIFIED WIDTH or DEPTH (inches)

Column 1 0.500-0.749 0.750-0.999 1.000-1.999 2.000-3.999 4.000-4.999 5.000-5.999 6.000-6.999 7.000-7.999 8.000-8.999 9.000-9.999 10.000-10.999 11.000-12.999

A

A

A

A Difference between AA and specified width or depth

SQUARE, RECTANGULAR Column 2 Other Alloys [16] Alloys 5083, 5086, 5454 .018 .012 .021 .014 .027 .018 .038 .025 .053 .035 .068 .045 .083 .055 .098 .065 .113 .075 .128 .085 .143 .095 .158 .105

Numbered footnotes follow Table 8-24. Excerpted from (ASD), 1997, Tables 12.2 and 12.3.

A

A

A

A

A

A

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

SQUARE, HEXAGONAL, OCTAGONAL Alloys 5083, Other Alloys [16] 5086, 5454 .030 .020 .030 .020 .038 .025 .053 .035 .068 .045 .083 .055 .098 .065 .108 .075 .123 .085 .143 .095 .158 .105 .173 .115

Aluminum Standards and Data

Section 8

Tolerances

RECTANGULAR Column 4 All Alloys The tolerance for the width is the value in the previous column for a dimension equal to the depth, and conversely, but in no case is the tolerance less than at the corners. Example: The width tolerance of a 1 X 3 inch alloy 6061 rectangular tube is ± 0.025 inch and the depth tolerance ±0.035 inch.

8-26

Table 8-14 Wall Thickness—Round Extruded Tube TOLERANCE[1] [2]-inches plus and minus ALLOWABLE DEVIATION OF MEAN WALL THICKNESS

SPECIFIED WALL THICKNESS [6] (inches)

[5]

ALLOWABLE DEVIATION OF WALL THICKNESS AT ANY POINT FROM MEAN WALL THICKNESS [5] (Eccentricity)

FROM SPECIFIED WALL THICKNESS

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

OUTSIDE DIAMETER-INCHES 1.250-2.999 3.000-4.999

Under 1.250

Column 1

Under 0.047 0.047-0.061 0.062-0.077 0.078-0.124 0.125-0.249 0.250-0.374 0.375-0.499 0.500-0.749 0.750-0.999 1.000-1.499 1.500-2.000 2.001-2.499 2.500-2.999 3.000-3.499 3.500-4.000

Column 2

Column 3

5.000 and over

Other Alloys [16]

Alloys 5083 5086 5454

Other Alloys [16]

.009 .011 .012 .014 .014 .017 .. .. .. .. .. .. .. .. ..

.006 .007 .008 .009 .009 .011 .. .. .. .. .. .. .. .. ..

.. .012 .012 .014 .014 .017 .023 .030 .. .. .. .. .. .. ..

.. .008 .008 .009 .009 .011 .015 .020 .. .. .. .. .. .. ..

Other Alloys [16]

Alloys 5083 5086 5454

.. .012 .014 .015 .020 .024 .032 .042 .053 .068 .. .. .. .. ..

A Difference between AA and mean wall thickness

Column 5

Column 4

Alloys 5083 5086 5454

A

Alloys 5083 5086 5454

.. .008 .009 .010 .013 .016 .021 .028 .035 .045 .. .. .. .. ..

.. .015 .018 .023 .030 .038 .053 .068 .083 .098 .113 .128 .143 .158 .173

Column 6

Other Alloys [16]

All Alloys

.. .010 .012 .015 .020 .025 .035 .045 .055 .065 .075 .085 .095 .105 .115

Plus and minus 10% of mean wall thickness max ± 0.060 min ± 0.010

± 0.120

TABLE 8-15 Wall Thickness—Other-than-Round Extruded Tube TOLERANCE[1] [2]-inches plus and minus SPECIFIED WALL THICKNESS [6] (inches)

A

A B

A

B

Under 5.000 Alloys 5083 5086 5454

.008 .009 .011 .012 .017 .021 .038 .053 .068 ..

Other Alloys [16]

.005 .006 .007 .008 .011 .014 .025 .035 .045 ..

Column 3 Alloys 5083 5086 5454

.012 .014 .015 .023 .030 .045 .060 .075 .090 .105

A

Difference between AA and mean wall thickness

CIRCUMSCRIBING CIRCLE DIAMETER [10]-inches 5.000 and over Under 5.000

Column 2

Column 1

A

A

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

Under 0.047 0.047-0.061 0.062-0.124 0.125-0.249 0.250-0.374 0.375-0.499 0.500-0.749 0.750-0.999 1.000-1.499 1.500-2.000

ALLOWABLE DEVIATION OF WALL THICKNESS [5] (Eccentricity)

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

Other Alloys [16]

.008 .009 .010 .015 .020 .030 .040 .050 .060 .070

5.000 and over

Column 4

Column 5

All Alloys

All Alloys

.005 .007 .010 .015 .025 .030 .040 .050 .060 ..

Plus and minus 10% of mean wall thickness max ± 0.060 min ± 0.010

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


8-27

TABLE 8-16 Length—Extruded Tube SPECIFIED OUTSIDE DIAMETER OR WIDTH (inches)

0.500-1.249 1.250-2.999 3.000-7.999 8.000 & over

TOLERANCE-inches plus excepted as noted ALLOWABLE DEVIATION FROM SPECIFIED LENGTH STRAIGHT

COILED SPECIFIED LENGTH-feet

Up through 12

1/8 1/8 3/16 1/4

TABLE 8-17 Twist

Over 12 through 30

Over 30 through 50

Over 50

Up through 100

Over 100 through 250

Over 250 through 500

Over 500

3/8 3/8 7/16 1/2

1 1 1 1

+5%, -0% .. .. ..

±10% .. .. ..

±15% .. .. ..

±20% .. .. ..

1/4 1/4 5/16 3/8

[11]

—Other-than-Round Tube TOLERANCE [9]-Degrees ALLOWABLE DEVIATION FROM STRAIGHT

TEMPER

SPECIFIED WIDTH (inches)

L

SPECIFIED THICKNESS (inches)

Y

Y (max.) in degrees IN TOTAL LENGTH OR IN ANY SEGMENT OF ONE FOOT OR MORE OF TOTAL LENGTH

All except O, TX510, TX511[8] TX510[8] TX511[8]

0.500-1.499 1.500-2.999 3.000 and over 0.500 and over 0.500-1.499 1.500-2.999 3.000 and over

All All All 0.095 and 0.095 and 0.095 and 0.095 and

SPECIFIED WIDTH (inches)

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

IN TOTAL LENGTH OR IN ANY SEGMENT OF ONE FOOT OR MORE OF TOTAL LENGTH

TX510[8]

0.500 and over

7 5 3

[7]

[7]

1 x Measured length, feet 1/2 x Measured length, feet 1/4 x Measured length, feet

7 5 3

Except for 0, T3510, T4510, T6510, T73510, T76510, & T8510 Tempers [7]

D

All except 0.500-5.999 O, TX510[8] 6.000 and over

1 x Measured length, feet 1/2 x Measured length, feet 1/4 x Measured length, feet

TABLE 8-19 Flatness (Flat Surfaces)

TABLE 8-18 Straightness—Tube in Straight Lengths

TEMPER

over over over over

MAXIMUM FOR TOTAL LENGTH

.010 x Measured length, feet .020 x Measured length, feet

TOLERANCE-inches MINIMUM THICKNESS OF METAL FORMING THE SURFACE (inches)

Up through 0.187 0.188 and over

Y

Maximum Allowable Deviation Y WIDTHS UP THROUGH 1INCH OR ANY 1-INCH INCREMENT OF WIDER SURFACES

0.006 0.004

WIDTHS OVER 1INCH THROUGH 5.999 INCHES

0.006 x W (inches) 0.004 x W (inches)

[7]

Section 8

Tolerances

8-28

Footnotes for Tables 8-12 through 8-24

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

When outside diameter, inside diameter, and wall thickness (or their equivalent dimensions in other-than-round tube) are all specified, standard tolerances are applicable to any two of these dimensions, but not to all three. When both outside and inside diameters or inside diameter and wall thickness are specified, the tolerance applicable to the specified or calculated O.D. dimension shall also apply to the I.D. dimension. [1]

TABLE 8-21 Corner and Fillet Radii SPECIFIED RADIUS (inches)

TOLERANCE-inches ALLOWABLE DEVIATION FROM SPECIFIED RADIUS

When a dimension tolerance is specified other than as an equal bilateral tolerance, the value of the standard tolerance is that which applied to the mean of the maximum and minimum dimensions permissible under the tolerance for the dimension under consideration. [2]

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

A

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

Difference between radius A and specified radius Sharp corners 0.016-0.187 0.188 and over

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

+1/64 ±1/64 ±10%

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

TABLE 8-22 Angularity

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

Allowable deviation from square: ± 2 degrees.

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. [8]

TABLE 8-23 Surface Roughness[14] [17] Specified Outside Diameter (inches)

Specified Wall Thickness (inches)

Allowable Depth of Conditions [13] (inches, max.)

[9]

When weight of piece on flat surface minimizes deviation.

The circumscribing circle diameter is the diameter of the smallest circle that will completely enclose the cross-section of the extruded product. [10]

Up through 12.750

Up through 0.063 0.064-0.125 0.126-0.188 0.189-0.250 0.251-0.500 0.501 and over 12.751-15.000 Up through 0.500 0.501 and over 15.001-20.000 Up through 0.500 0.501 and over 20.001 and over Up through 0.500 0.501 and over

0.0025 0.003 0.0035 0.004 0.005 0.008 0.010 0.012 0.012 0.015 0.015 0.020

[11]

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

[13]

Conditions include die lines, mandrel lines, and handling marks.

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

[15]

Not applicable to O temper tube.

[16]

Limited to those alloys listed in ASD, Table 12.1.

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 for tube having a wall thickness less than 2 1/2 percent 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.)

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

Not applicable to 2219 alloy tube. Most tubes in 2219 alloy will have die lines about twice the depth shown in the table; however, for each tube size the supplier should be contacted for the roughness value to apply. [17]

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

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


8-29

PROPERTIES AND TOLERANCES FOR EXTRUDED COILED TUBE Application Extruded round coiled tube is produced by bridge or porthole die extrusion methods and is intended for general purpose applications such as refrigeration units, oil lines, and instrument lines. Internal Cleanliness The tube shall be capable of meeting an inside cleanliness requirement of no more residue than 0.002 g of residue per square foot (0.139 x 10-4g per square inch) of internal surface when tested in accordance with the following paragraph. Tube ends are sealed by crimping or by other suitable means to 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 aspirated through a test sample of tube into the flask. The test sample shall have a minimum internal area of 375 square inches, except that no more than 50 feet of length shall be required. The solvent is then transferred to a preweighed container such as a crucible, evaporating dish, or beaker and completely evaporated on a lowtemperature hot plate. After solvent evaporation, the container 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 for the blank is subtracted from the weight of the residue sample. The corrected weight is then calculated in grams of residue per internal area of tube. Note: The quantity of solvent used for the blank run is the

same as that used for the actual examination of the tube sample. The sample is prepared so that there is no inclusion of chips, dust, and so forth, resulting from the sample preparation.

Leak Test The tube is capable of withstanding an internal air pressure of 250 psi with no evidence of leakage or pressure loss. Formability The tube ends are capable of being expanded by forcing a steel pin having an included angle of 60 degrees into them until the outside diameter is increased 40 percent. The expansion shall not cause cracks, ruptures, or other defects visible to the unaided eye.

Section 8

Tolerances

8-30

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

SPECIFIED WALL THICKNESS (inches)

ALLOY AND TEMPER [3]

1050-H112 1100-H112 1200-H112 1235-H112 3003-H112

ELONGATION percent min. in 2 inches

ULTIMATE

0.032-0.050 0.032-0.050 0.032-0.050 0.032-0.050 0.032-0.050

min

max

YIELD min.

8.5 11.0 10.0 9.0 14.0

14.5 17.0 16.0 15.0 20.0

2.5 3.0 3.0 3.0 5.0

FULL-SECTION SPECIMEN

25 25 25 25 25

TABLE 8-26 Outside Diameter SPECIFIED OUTSIDE DIAMETER (inches)

TOLERANCE-inches plus and minus ALLOWABLE DEVIATION OF MEAN DIAMETER FROM SPECIFIED DIAMETER

0.250-0.625

ALLOWABLE DEVIATION OF DIAMETER AT ANY POINT FROM SPECIFIED DIAMETER

0.004

0.006

TABLE 8-27 Wall Thickness SPECIFIED WALL THICKNESS (inches)

TOLERANCE-inches plus and minus ALLOWABLE DEVIATION OF MEAN WALL THICKNESS FROM SPECIFIED WALL THICKNESS

ALLOWABLE DEVIATION OF WALL THICKNESS AT ANY POINT FROM SPECIFIED WALL THICKNESS

0.003

0.004

0.032-0.050

TABLE 8-28 Coil Length [4] PERCENT OF COILS IN SHIPMENT

RANGE OF LENGTH

70 min. 30 max.

80 to 120 percent of nominal 60 to 80 percent of nominal

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 f lattening, leveling, or straightening coiled products subsequent to shipment by the producer may alter the mechanical properties of the 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.


8-31

Section 8

Tolerances

Section

8

TOLERANCES GEOMETRIC TOLERANCING

universal engineering drawing language and technique that companies, industries, and government are finding essential to their operational well-being. Over the past 30 years, this subject has matured to become an indispensable manageTaken together, geometric dimension- ment tool; it assists productivity, quality, and economics in producing and ing and tolerancing can be used to marketing products around the specify the geometry or shape of an extrusion on an engineering drawing. world. It can be described as a modern technical language, which has uniform RATIONALE OF meaning to all, and can vastly GEOMETRIC improve communication in the cycle DIMENSIONING AND from design to manufacture. Terminology, however, varies in mean- TOLERANCING Geometric dimensioning and tolering according to the Geometric ancing builds upon previously estabStandard being used; this must be lished drawing practices. It adds, taken into account in each case. however, a new dimension to drawing skills in defining the part and its feaGeometric dimensioning and tolertures, beyond the capabilities of the ancing, also referred to in colloquial older methods. terms as geometrics, is based upon sound engineering and manufacturIt is sometimes effective to consider ing principles. It more readily capthe technical benefits of geometric tures the design intent by providing dimensioning and tolerancing by designers and drafters better tools examining and analyzing a drawing with which to "say what they mean." Hence, the people involved in manu- without such techniques used, putting the interpretation of such a facturing or production can more clearly understand the design require- drawing to the test of clarity. Have the requirements of such a part been ments. In practice, it becomes quite adequately stated? Can it be proevident that the basic "engineering" duced with the clearest understand(in terms of extruding, fixturing, inspecting, etc.) is more logically con- ing? Geometric dimensioning and tolerancing offers that clarity. sistent with the design intent when geometric dimensioning and tolerOften an engineer is concerned ancing is used. As one example, about fit and function. With many functional gauging can be used to standard tolerances this may become facilitate the verification process and, a concern. Geometric tolerancing is at the same time, protect design structured to better control parts in a intent. Geometric dimensioning and tolerancing is also rapidly becoming a fit-and-function relationship.

INTRODUCTION TO GEOMETRIC DIMENSIONING AND TOLERANCING


8-33

THE SYMBOLS

STRAIGHTNESS

Effective implementation of geometrics first requires a good grasp of the many different symbols and their functional meaning. The following symbols are those that are most commonly used within the extrusion industry.

FLATNESS

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

POSITION

For definitions of basic terms used in geometric tolerancing, refer to the appendix at the end of this section.

CYLINDRICITY

ANGULARITY PERPENDICULARITY PARALLELISM CONCENTRICITY

CIRCULARITY PROFILE OF A LINE PROFILE OF A SURFACE

DIAMETER DATUM FEATURE

Tolerances used within the following examples are purely illustrative and may not reflect the standard tolerances used by the aluminum extrusion industry. Note:

THE FEATURE CONTROL

MAXIMUM MATERIAL CONDITION (MMC)

A

or

M

REGARDLESS OF FEATURE SIZE (RFS)

S

LEAST MATERIAL CONDITION (LMC)

L

TANGENT PLANE

T

This feature is to be in: “POSITION” WITHIN

FRAME

The feature control frame is a rectangular box containing the geometric characteristics symbol and the form, orientation, profile, runout, or location tolerance. If necessary, datum references and modifiers applicable to the feature of the datums are also contained in the frame.

A

A CYLINDRICAL TOLERANCE OF 0.020

M

A

B

C

0.020 TOTAL when the feature is produced AT MAXIMUM MATERIAL CONDITION WITH RESPECT TO

Section 8

Tolerances

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

8-34

MATERIAL CONDITIONS Maximum Material Condition

The abbreviation for maximum material condition is MMC and the symbol is the capital letter M with a circle around it. The maximum material condition occurs when a feature contains the most material allowed by the size tolerance. It is the condition that will cause the feature to weigh the most. MMC is often considered when the designer's concern is assembly. The minimum clearance or maximum interference between mating parts will occur when the part features are at MMC. The maximum material condition for external features occurs when the size dimension is at its largest. The maximum material condition for internal features occurs when the size dimension is at its smallest. MMC - abbreviation M

- symbol

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

Regardless of Feature Size

The abbreviation for regardless of feature size is RFS, and the symbol is S within a circle. Regardless of feature size is a condition that is used when the importance of location and/or shape of a feature is independent of the feature's size and forces anyone checking the part to use open set-up inspection. RFS - abbreviation

Least Material Condition

The abbreviation for least material condition is LMC and the symbol is L within a circle. Least material condition is the opposite of maximum material condition. In other words, it is a condition of a feature where it contains the least amount of material. For external parts, that occurs when the overall dimension is at a maximum. It is the maximum size of an internal feature. LMC - abbreviation L

S

- symbol

RULE # 1 - “Where only a tolerance of size is specified,

the limits of size of an individual feature prescribe the extent to which variations in its geometric form, as well as size, are allowed.” Rule # 2 - “For all applicable geometric tolerances, RFS

applies with respect to individual tolerance, datum reference, or both, where no modifying symbol is specified. MMC, or LMC, must be specified on the drawing where it is required.”

- symbol


8-35

DATUMS A datum is a theoretically exact point, axis, or plane that is derived from the true geometric counterpart of a specified datum feature. The datum is the origin from which the location or orientation of part features is established. Confusion can arise if the drawing does not specify how a part is to be located. This is done by specifying datums on the drawing.

A

B C

A drawing of a ball bearing would not require a datum because it is a single feature part. If a hole were drilled in the ball bearing, different measurements would result if the tolerance of the part were held to be on the feature of the ball or the hole. Adding a datum designation to one of these features and referencing to it would eliminate any confusion. The datum feature is defined as the actual feature of a part that is used to establish the datum. Since it is not possible to establish a theoretically exact datum, datums must be simulated. Typical ways to simulate a datum are to use surface plates, angle plates, gauge pins, collets, machine tool beds, etc. The intent of the standard is to hold or fixture the part with something that is as close to the true geometric counterpart as possible. The further the fixture deviates from the true geometric counterpart, the greater the set-up error and, therefore, the less reliable the measurement.

Simulated datums are what hold the parts in production, inspection, and their assembly.

ANSI Prior to 1994

ASME 1994 and ISO

-AA

Theoretically Perfect

Either Method Means The Following: Simulated Datum

Datum Feature

Mating Part

Measurements Are Made From Simulated Datums

Section 8

Tolerances

8-36

The datums can be thought of as a navigation system for dimensions of the part. They might also be thought of as a "trap" for the part. On the lower drawing on the opposite page, the datum, in this case datum A, refers to a theoretically perfect datum plane. A surface plate in an inspection area would serve as a simulated datum and would make contact on the high points or extremities of the surface.

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). The 0.480 can float within the 0.520. If the lower surface was perfectly flat (right--hand figure), the upper surface could be anywhere within a 0.040 tolerance zone. In this extreme case, it can be said that the top surface must be flat within 0.040.

0.500±0.020

These high points are the same points that will make contact with the mating part in the final assembly. Measurements made from the surface plate to other features on the part will be the best method to predict whether the part will per form its intended function. 0.520 0.480

TOLERANCES OF FORM (Unrelated) If the part is manufactured at MMC, both surfaces would have to be perfectly flat.

The geometric form of a feature is controlled first by a size dimension. Prior to the use of geometric dimensioning and tolerancing, size dimension was the primary control of form and did not prove to be sufficient. In some cases, it is too restrictive and in others, the meaning is unclear. Rule Number 1 (see page 8-35) clearly states the degree to which size controls form.


8-37

FLATNESS

M

Flatness is the condition of a surface having all elements in one plane.

,

or

S

L

not allowed

0.006 A

Flatness usually applies to a surface being used as a primary datum feature.

Never a datum reference

Other tolerances that provide flatness control include: 1.000±0.010

•Any size tolerance on a feature comprised of two internal or external parallel opposed planes. •Any flat surface being controlled by: Perpendicularity

0.008 A

Parallelism

0.008 A

Angularity

0.008 A

Profile of a Surface

0.010 A B

Total Runout

0.010 A

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

Flatness Placement

0.006

or

0.006

The flatness requirement is placed in a view where the controlled 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 flat surfaces, it should never be placed next to a size dimension.

Section 8

Tolerances

8-38

STRAIGHTNESS (of an axis or center plane)

Straightness is a condition under which an element of a sur face or an axis is a straight line.

0.005 S

0.005

M

is implied per Rule # 2 (since 1994) &

L

are allowed

The feature control frame must be located with the size dimension. This tolerance is used as a way to override the requirement of perfect form at MMC (Rule #1). Other tolerancing that automatically provides this control are: Any Size Tolerances

±0.010

Circular Runout

0.006 A

Total Runout

0.010 A

0.005 The straightness tolerance can be used whenever a straight line element, axis, or center plane can be identified on a part. The tolerance zones used for straightness can be either a pair of parallel lines or a cylinder. Each line element, axis, or center plane is compared to the tolerance zone. The tolerance for line elements is shown on the drawing in a view where the elements to be controlled are shown as straight lines.

Front

Front

0.470±0.005

t o n r F


8-39

SURFACE STRAIGHTNESS (on a flat surface, cylinder, or cone)

Other tolerances that provide flatness control include:

M

,

S

or

L

not allowed

0.004 Never a datum reference

• Any size tolerance on a feature comprised of two internal or external parallel opposed planes. 1.000±0.010

The straightness in this case would be 0.020.

• Any flat surface being controlled by:

Perpendicularity

0.008 A

Parallelism

0.008 A

Angularity

0.008 A


0.010 A B

Total Runout

0.010 A

Flatness

0.006

Cylindricity

0.006

Section 8

Tolerances

8-40

CIRCULARITY (roundness)

M

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) passing through a common center (sphere) are equidistant from the center.

,

S

or

L

not allowed


Other tolerances that provide circularity control include: • Any size tolerance on a cylindrical feature or sphere. • Any feature containing circular elements and being controlled by: Circular Runout

0.006 A

Total Runout

0.010 A

Rule of thumb: Runout tolerances are usually less expensive to verify and should be considered when circularity is desired. The tolerance will be on a leader line, which points to the feature containing the circular element(s). Circularity is similar to straightness except that the tolerance zone is perfectly circular rather than perfectly straight. Although the circularity tolerance floats within the limits of size, it is independent of size and should not be placed next to the size dimension.

Every circular element must be within the tolerance zone.

These two diameters can be of any diameters within the size limits of the feature, provided they remain concentric and their radial difference equals the circularity tolerance.

0.006

0.750±0.005


8-41

CYLINDRICITY Cylindricity is a condition of a surface of revolution in which all points of the surface are equidistant from a common axis.

M

,

S

or

L

not allowed


Other tolerances that provide the control of cylindricity include: • Any size tolerance on a cylindrical feature. • Any feature containing cylindrical features being controlled by: Total Runout

0.006 0.820±0.005

0.010 A

Rule of thumb: Total runout is usually more cost effective to verify and should be considered when cylindricity is desired. - No datum reference - Independent of size - May not be modified - Does not locate or orient.

Width of Cylindricity Tolerance Zone Tolerance Zone is created by two concentric cylinders

Section 8

Tolerances

8-42

ORIENTATION TOLERANCES Orientation tolerances are applicable to related features, where one feature is selected as a datum feature and the other related to it. Orientation tolerances are perpendicularity, angularity, and parallelism. Orientation tolerances control the orientation of a feature with respect to a datum that is established by a different part feature (the datum feature).

For that reason, the tolerance will always include at least one datum reference. Orientation tolerances are considered on a “regardless of feature size” basis unless the maximum material condition modifier is added. The important thing to remember about orientation tolerances is that they do not locate features. Because of that, with the exception of perpendicularity on a secondary datum feature or a plane surface, orientation tolerances should not be the only geometric control on a feature. They should, instead, be used as a refinement of a tolerance that locates the feature.

0.20

A

0.20

A

37°

0.20

A

A


8-43

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

Datum reference required (minimum of one)

0.008

Perpendicularity is used on a secondary datum feature, relative to the primary datum. It may be used to a tertiary datum feature not requiring location.

0.008

A

M

or L

S

is implied per Rule #2 (since 1994)

A

is permitted

Other tolerances that may provide perpendicularity include: Position

0.020

M

A B


0.010 A B

Total Runout

0.010 A

The perpendicularity tolerance is specified by being placed on an extension line. The tolerance zone is defined by a pair of parallel planes 0.2 mm apart. The tolerance zone is perfectly perpendicular to the datum plane -A-. The tolerance zone may be thought of as a flatness tolerance zone that is oriented at exactly 90 degrees to the datum. 0.20 A

M

Therefore, perpendicularity should usually be used as a

0.020 M A B M 0.008 A

A

The perpendicularity of features of size may also be controlled. The tolerance will be associated with the size dimension. When the size dimension applies to a pair of parallel planes (a slot or tab), the median or center plane is controlled by the tolerance. 50.00±0.06 A 0.20 A

Could be modified RFS is implied

M

or

L

Section 8

Tolerances

8-44


PARALLELISM When parallelism is applied to a flat surface, parallelism automatically provides flatness control and is usually easier to measure.

0.008

0.008 A M

Required when the feature and the datum feature are both cylindrical

S

or L

A

is permitted


Other tolerances that may provide parallelism include: Any size tolerance on a feature composed of two internal or external parallel planes.

Features are considered parallel when the distance between them remains constant. Two lines, two surfaces, or a surface and a line may be parallel. The parallelism of features on a part is controlled by making one a datum feature and specifying a parallelism tolerance with respect to it. When parallelism is applied to a plane that is part of a feature of size and the other plane of that feature is the referenced datum feature, the parallelism tolerance cannot be greater than or equal to the total size tolerance or it would be meaningless since the plane's parallelism is automatically controlled by the size dimension. Parallelism can also be specified on an MMC basis. The MMC modifier can be on the feature tolerance, the datum feature, or both. As the feature deviates from its maximum material condition, the parallelism tolerance is increased.

Position

0.020


0.010 A B

Total Runout

0.010 A B

M

A B

M

If the primary datum is a plane

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

0.1

A

20.0±0.4

A

o4.5±0.1

0.4 0.1

M M

A A

12

A Aluminum Extrusion Manual

8-45

ANGULARITY


Angularity is the condition of a surface, axis, or center plane which is at a specified angle (other than 90 degrees) from a datum plane or axis. Angularity, as a tolerance, always requires a BASIC angle.

0.008 A o not allowed

Other tolerances that may provide angular control of features include:

M

or

S

is implied per Rule #2

L

• A tolerance in degrees applied to an angular dimension (not BASIC), provided there is a general note on the drawing relating toleranced dimensions to a datum reference frame. Position

0.020


M

A B

M

0.010 A B

Therefore, angularity should usually be used as a refinement of one of the above: 0.020 0.008

M

A B

M

0.20

A

37°

A

Angularity is used to control the orientation of features to a datum axis or datum plane when they are at some angle other than 0 or 90 degrees. Since angularity does not locate features, it should only be considered after the feature is located. Usually a locating tolerance such as position or profile will do an adequate job of controlling the angularity and further refinement will not be necessary. A Basic Angle must always be applied to the feature from the referenced datum.

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.

Section 8

Tolerances

8-46

PROFILE Profile is one of the least used--and yet most useful--geometric tolerances available. There are two types of profile tolerance: profile of a line and profile of a surface. The profile tolerances are the only geometric tolerances that may have a datum reference or may not. Without a datum reference in the feature control frame, the profile tolerance is controlling form. Profile of a line is very similar to the control seen with straightness or circularity. Profile of a surface is similar to the flatness or cylindricity tolerance. Care should be exercised in using profile without a datum. It usually makes the inspection of the part more difficult. With a datum reference, the profile tolerance may control form, orientation, and location. Under certain conditions, profile may also control size. When a profile tolerance is used on the drawing, the tolerance is implied to be centered on the surface of the feature that has been defined by basic dimensions. If it is desired that the profile tolerance apply only in one direction, this can be illustrated on the drawing using a phantom line to indicate the side of the surface to which the tolerance should apply. This method of specifying the tolerance in only one direction is extremely useful for applications such as a punch and die in tooling or a cover on a housing where the internal and external features have an irregular shape. The basic shape of the object being controlled with profile must be dimensioned or defined using basic dimensions.

Profile of a Line Profile of a Surface

0.020 A Bilateral Tolerance Zone

0.020 A Unilateral Tolerance Zone (Outside)

0.020 A Unilateral Tolerance Zone (Inside)

The tolerance zone is implied to be centered on the basic surface unless shown otherwise on the drawing


8-47

PROFILE OF A SURFACE Profile of a surface is the condition permitting a uniform amount of a profile variation, either unilaterally or bilaterally, on a surface. (Profile tolerances are the only geometric tolerances where datum referencing is optional.)

0.004 A Without a datum reference, profile of a surface controls the form of the surface (similar to straightness or circularity).

Form, orientation, and location may be controlled through datum referencing. If a size dimension is made basic, profile of a surface may also control size. The shape of the feature must be described using basic dimensions.

0.010 A B or

M S

,

M

or

L

L

is permitted (not recommended)

is not permitted S

is implied

The best application of profile of a surface is to locate plane and contoured surfaces. When irregular parts must fit together, the use of unilateral profile tolerancing makes tolerance analysis easy for the designer. This approach may make manufacturing and inspection more difficult since many computer numerically controlled (CNC) machine tools and inspection machines now use the CAD file, which should usually be created at the goal or middle values.

All around symbol

0.008

Section 8

0.008

Tolerances

8-48

PROFILE OF A LINE Profile of a line is the condition permitting a uniform amount of profile variation, either unilaterally or bilaterally, along a line element of a feature. (Profile tolerances are the only geometric tolerances where datum referencing is optional.)

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

0.010 A B

Both form and orientation are controlled through datum referencing.

M S

Unless dealing with thin parts, profile of a surface is a better choice for location.

,

M

L

or

or

L

is permitted (not recommended)

is not permitted S

is implied

The shape of the feature must be described using basic dimensions. 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.

0.010 A B 0.004 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.

0.1 T A

TANGENT PLANE Tangent plane is a new concept/symbol, introduced in the 1994 Standard. Normally when a surface is inspected for Perpendicularity, Parallelism, Angularity, Profile of a Surface, or Total Runout, the flatness must also fall within the aforementioned geometric tolerance or the part would fail. Tangent Plane exempts the flatness requirement. The gauge block is intended to simulate the mating part.

20.0±0.4

A

Ga uge B loc k


Ignore the out-of-flat condition when checking parallelism.

8-49

CONCENTRICITY Concentricity is a condition in which two or more features (cylinders, cones, spheres, hexagons, etc.) in any combination have a common axis. The datum(s) referenced must establish an axis.

S


M

& L

0.010 A

are not allowed

Required

Consider circular runout instead of concentricity: • Runout is easier to verify • Runout also controls the form of the feature. Concentricity is a static attempt to control dynamic balance.

Section 8

Tolerances

8-50

APPENDIX to Section 8 Basic Terminology for Geometric Tolerancing

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

actual size —- An actual size is the measured size of the feature.

concentricity —- Concentricity is a condition in which two or more features (cylinders, cones, spheres, hexagons, etc.) in any combination have a common axis.

angularity —- Angularity is the condition of a surface, axis, or center plane, which is at a specified angle (other than 90 degrees) from a datum plane or axis. basic dimension —- A dimension specified on a drawing as Basic (or abbreviated BSC) is a theoretical value used to describe the exact size, shape, or location of a feature. It is used as the basis from which permissible variations are established by tolerances on other dimensions or notes. basic size —- The basic size is that size from which limits of size are derived by the application of allowances and tolerances. bilateral tolerancing —- A bilateral tolerance is a tolerance in which variation is permitted in both directions from the specified dimension. center plane —- Center plane is the middle or median plane of a feature. circular runout —- Circular runout is the composite control of circular elements of a surface independently at any circular measuring position as the part is rotated through 360 degrees. circularity —- 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) 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 a clearance always results when mating parts are assembled.

contour tolerancing —- See profile of a line or profile of a surface. cylindricity —- Cylindricity is a condition of a surface of revolution in which all points of the surface are equidistant from a common axis. datum —- A datum is a theoretically exact point, axis, or plane derived from the true geometric counterpart of a specified datum feature. A datum is the origin from which the location or geometric characteristics of features of a part are established. datum axis —- The datum axis is the theoretically exact center line of the datum cylinder as established by the extremities or contacting 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 part which is used to establish a datum. datum feature symbol —- The datum feature symbol contains the datum reference letter in a rectangular box. datum line —- A datum line is that which has length but no breadth or depth such as the intersection line of two planes, center line or axis of holes or cylinders, reference line for functional, tooling, or gauging purposes. A datum line is derived from the true geometric counterpart of a specified datum feature when applied in geometric tolerancing. datum plane —- A datum plane is a theoretically exact plane established by the extremities or contacting points of the datum feature (surface) with a simulated datum plane (surface plate or other checking device). A datum plane is derived from the true geometric counterpart of a specified datum feature when applied in geometric tolerancing. datum point —- A datum point is that which has position but no extent such as the apex of a pyramid or cone, center point of a sphere, or reference point on a surface for functional, tooling, or gauging purposes. A datum point is derived from a specified datum target on a part feature when applied in geometric tolerancing.


8-51

datum reference —- A datum reference is a datum feature as specified on a drawing. datum reference frame —- A datum reference frame is a system of three mutually perpendicular datum planes or axes established from datum features as a basis for dimensions for design, manufacture, and verification. It provides complete orientation for the feature involved. datum surface —- A datum surface or feature (hole, slot, diameter, etc.) refers to the actual part surface or feature coincidental with, relative to, and/or used to establish a datum. datum target —- A datum target is a specified datum point, line, or area (identified on the drawing with a datum target symbol) used to establish datum points, lines, planes, or areas for special function, or manufacturing and inspection repeatability. dimension —- A dimension is a numerical value expressed in appropriate units of measure and indicated on a drawing. feature —- Feature is the general term applied to a physical portion of a part, such as a surface, hole, pin, slot, tab, etc. feature of size —- A feature of size may be one cylindrical or spherical surface, or a set of two plane parallel surfaces, each of which is associated with a dimension; it may be a feature such as hole, shaft, pin, slot, etc. which has an axis, centerline, or centerplane when related to geometric tolerances. feature control frame —- The feature control frame is a rectangular box containing the geometric characteristic symbol and the form, orientation, profile, runout, or location tolerance. If necessary, datum references and modifiers applicable to the feature of the datums are also contained in the frame.

fit —- Fit is the general term used to signify the range of tightness or looseness which may result from the application of a specific combination of allowances and tolerance on the design of mating part features. Fits are of four general types: clearance, interference, transition, and line. flatness —- Flatness is the condition of a surface having all elements in one plane. form tolerance —- A form tolerance states how far an actual surface or feature is permitted to vary from the desired form implied by the drawing. Expressions of these tolerances refer to flatness, straightness, circularity, and cylindricity. full indicator movement (FIM) (see also FIR and TIR) —- Full indicator movement is the total movement observed with the dial indicator (or comparable measuring device) in contact with the part feature surface during one full revolution of the part about its datum axis. Full indicator movement (FIM) is the term used internationally. United States terms FIR, and TIR, used in the past, have the same meaning as FIM. Full indicator movement also refers to the total indicator movement observed while in traverse over a fixed noncircular shape. full indicator reading (FIR) —- Full indicator reading is the total indicator movement reading observed with the dial indicator in contact with the part feature surface during one full revolution of 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 reading observed while in traverse over a fixed noncircular shape. geometric characteristics —- Geometric characteristics refer to the basic elements or building blocks which form the language of geometric dimensioning and tolerancing. Generally, the term refers to all the symbols used in form, orientation, profile, runout, and location tolerancing. implied datum —- An implied datum is an unspecified datum whose influence on the application is implied by the dimensional arrangement on the drawing—e.g., the primary dimensions are tied to an edge surface; this edge is implied as a datum surface and plane. interference fit —- An interference fit is one having limits of size so prescribed that an interference always results when mating parts are assembled.

Section 8

Tolerances

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interrelated datum reference frame — An interrelated datum reference frame is one which has one or more common datums with another datum reference frame.

maximum dimension —- A maximum dimension represents the acceptable upper limit. The lower limit may be considered any value less than the maximum specified.

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

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

limits of size —- The limits of size are the specified maximum and minimum sizes of a feature. limit dimensions (tolerancing) —- In limit dimensioning only the maximum and minimum dimensions are specified. When used with dimension lines, the maximum value is placed above the minimum value, e.g., .300 - .295. When used 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 specified maximum and minimum sizes of a feature.

minimum material condition —- See least material condition.

multiple datum reference frames —- Multiple datum reference frames are more than one datum reference frame on one part. nominal size —- The nominal size is the stated designation which is used for the purpose of general identification, e.g., 1.400, .060, etc. normality —- See perpendicularity. orientation tolerance —- Orientation tolerances are applicable to related features, where one feature is selected as a datum feature and the other related to it. Orientation tolerances are perpendicularity, angularity, and parallelism. parallelepiped —- This refers to the shape of the tolerance zone. The term is used where total width is required and to describe geometrically a square or rectangular prism, or a solid with six faces, each of which is a parallelogram.

location tolerance —- A location tolerance states how far an actual feature may vary from the perfect location implied by the drawing as related to datums or other features. Expressions of these tolerances refer to the category of geometric characteristics containing position and concentricity (formerly also symmetry).

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

maximum material condition (MMC) —Maximum material condition is that condition where a feature of size contains the maximum amount of material within the stated limits of size, e.g., minimum hole diameter and maximum shaft diameter. It is opposite to least material condition.

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

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 of line —- Profile of line is the condition permitting a uniform amount of profile variation, either unilaterally or bilaterally, along a line element of a feature. profile of surface —- Profile of a surface is the condition permitting a uniform amount of profile variation, either unilaterally or bilaterally, on a surface.


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Tolerances Aluminum Extrusions Manual

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