Section
8
Tolerances
How straight is straight enough? How flat is flat
enough? How uniform must a wall thickness be
in order to be acceptable? These are not
abstract questions. Many products must be
manufactured to exacting 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. 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 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. 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
8-1
Where Are Dimensional 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
Surface
Roughness
End Cut Squareness
(Vertical & Transverse
Contour
(Curved Surfaces)
Corner & Fillet
Radii
C
A
A
Angularity
Flatness
Aluminum Extrusion Manual
8-3
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
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
Cross-section
or profile
dimensions
Tolerance
± .008 per inch
of measured
dimension
Cutting length
Piece parts
Press parts
± .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.
Aluminum Extrusion Manual
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) 7
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
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
Aluminum Extrusion Manual
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
(D)
(C)
(B)
(A)
5.900"(L)
0.200" (G)(TYP.)
2.000" (M)
H
2.000"
2.000"
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.
2.000"
2.000" 2.000" 2.000"
1.600"
(K)
• A lower horizontal leg 9" long.
(E)
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.
9"
9.21
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.”
Aluminum Extrusion Manual
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
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"
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.
Aluminum Extrusion Manual
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.
Aluminum Extrusion Manual
8-15
Step 7:
Identify the Space Dimensions
The Example
(F)
(E)
(D)
(C)
(B)
(A)
5.900"(L)
Their tolerances are found under
the general heading of “Space
Dimensions” on the standard
tolerance table.
2.000"
2.000"
0.200" (H)
H
0.200" (G)(TYP.)
Method: Space dimensions are those
measurements that include less than
75 percent metal (and so more than
25 percent open space).
2.000" (M)
2.000"
2.000" 2.000" 2.000"
1.600"
(K)
Purpose: To identify space dimensions and locate the section of the
tolerance table that includes them.
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)
O
S
Di
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)
i
Aluminum Extrusion Manual
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"
0.250"
F
E
D
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"
±.048" ±.038" ±.034"
Specified
2.000"
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
E
D
C
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.
Distance from Leg Dimension-Tolerance
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:
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
Aluminum Extrusion Manual
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.
Aluminum Extrusion Manual
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
..
..
..
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
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.
..
0.500 and over
0.500 and over
0.500 and over
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.
[5]
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.
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
SPECIFIED
THICKNESS
(RECTANGLES):
MINIMUM
THICKNESS
(PROFILES):
(inches)
TOLERANCE[3]—
degrees
Y
IN TOTAL LENGTH OR IN ANY
MEASURED SEGMENT OF
ONE FOOT OR MORE OF
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.
Up through 0.094[7]
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.
MAXIMUM
FOR TOTAL
LENGTH
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
UP
TO
5.999
6.000
TO
7.999
8.000
TO
9.999
.004
.004
.004
.004
.004
.004
.004
.004
.004
.004
.006
.006
.006
.006
.004
.004
.004
.004
.004
.004
.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
.014
.014
..
..
..
..
.010
.012
.012
.012
.014
.014
..
..
.008
.010
.010
.012
.012
.012
.014
..
.008
.008
.008
.010
.010
.010
.012
.014
.006
.008
.008
.008
.008
.010
.010
.012
.006
.008
.008
.008
.008
.008
.008
.010
.006
.006
.008
.008
.008
.008
.008
.008
.004
.006
.006
.006
.008
.008
.008
.008
.004
.004
.006
.006
.006
.008
.008
.008
Excerpted from Aluminum Standards and Data (ASD), 1997, Tables 11.7 and 11.8
Aluminum Extrusion Manual
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 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
UP
TO
5.999
6.000
TO
7.999
8.000
TO
9.999
.006
.006
.004
.004
.004
.004
.004
.004
.008
.008
.006
.006
.006
.004
.004
.004
.012
.010
.010
.008
.008
.006
.006
.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
Table 8-7 Surface Roughness[1]
Wire Rod, Bar & Profiles (Shapes)
SPECIFIED SECTION ALLOWABLE DEPTH
OF CONDITIONS[2]
THICKNESS (inches)
(inches, max)
Up through 0.063
.0015
0.064-0.125
.002
0.126-0.188
.0025
0.189-0.250
.003
0.251-0.500
.004
0.501-and over
.008
TOLERANCE
.016
..
..
.014
.016
..
.012
.014
.014
.010
.012
.012
.010
.010
.010
.008
.008
.008
.006
.008
.008
.006
.006
.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]
Allowable deviation from square: 1 degree
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]
— Profiles (Shapes)
A
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
specified contour: 0.005 inch per
TX510[4]
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
COL. 3[6]
COL. 2[6]
COL. 3[7]
COL. 2
COL. 3[7]
RATIO:
LEG OR SURFACE
LENGTH TO LEG OR METAL
THICKNESS
[6] [7]
[4]
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.
[5]
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.
MINIMUM
SPECIFIED LEG
THICKNESS
(inches)
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.
Aluminum Extrusion Manual
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]
ALLOWABLE DEVIATION OF DIAMETER AT ANY POINT
FROM SPECIFIED DIAMETER [4]
FROM
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
8.000
10.000
12.000
14.000
16.000
-
0.999
1.999
3.999
5.999
7.999
- 9.999
-11.999
-13.999
-15.999
-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
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
[16]
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
Numbered footnotes follow Table 8-24. Excerpted from Aluminum Standards and Data
(ASD), 1997, Tables 12.2 and 12.3.
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
..
..
..
..
..
..
..
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
Column 6
Other
Alloys [16]
Alloys
5083
5086
5454
Other
Alloys [16]
All Alloys
..
.008
.009
.010
.013
.016
.021
.028
.035
.045
..
..
..
..
..
..
.015
.018
.023
.030
.038
.053
.068
.083
.098
.113
.128
.143
.158
.173
..
.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
..
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
Column 3
Alloys 5083
5086 5454
.012
.014
.015
.023
.030
.045
.060
.075
.090
.105
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.
Aluminum Extrusion Manual
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
L
TEMPER
SPECIFIED
WIDTH
(inches)
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
TEMPER
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
over
over
over
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
SPECIFIED
WIDTH
(inches)
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.
[1]
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.
TABLE 8-21 Corner and Fillet Radii
SPECIFIED
RADIUS
(inches)
TOLERANCE-inches
ALLOWABLE
DEVIATION FROM
SPECIFIED RADIUS
[2]
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.
[3]
Mean diameter is the average of two diameter measurements
taken at right angles to each other at any point along the length.
A
[4]
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.
Difference between
radius A and
specified radius
Sharp corners
0.016-0.187
0.188 and over
[5]
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.
+1/64
±1/64
±10%
[6]
When dimensions specified are outside and inside, rather than wall
thickness itself, allowable deviation at any point (eccentricity) applies
to mean wall thickness.
TABLE 8-22 Angularity
[7]
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.
Allowable deviation from square: ± 2 degrees.
TABLE 8-23 Surface Roughness[14] [17]
Specified Outside
Diameter
(inches)
Specified Wall
Thickness
(inches)
Allowable Depth
of Conditions [13]
(inches, max.)
[8]
Tempers TX510 and TX511 are general designations for the
following stress-relieved tempers: T3510, T4510, T6510, T8510,
T73510, T76510; and T3511, T4511, T6511, T8511, T73511, T76511,
respectively.
[9]
When weight of piece on flat surface minimizes deviation.
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
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.)
[11]
See ASD, Standards Section (6), for Application of Twist limits.
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.
[14]
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.
[15]
Not applicable to O temper tube.
[16]
Limited to those alloys listed in ASD, Table 12.1.
[17]
Not applicable to 2219 alloy tube. Most tubes in 2219 alloy 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.
[18]
If unspecified, the radius shall be 1/32 inch maximum including
tolerances.
Excerpted from Aluminum Standards and Data (ASD), 1997,
Tables 12.10, 12.11, 12.12, 12.13, and 12.14.
Aluminum Extrusion Manual
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
1050-H112
1100-H112
1200-H112
1235-H112
3003-H112
ELONGATION
percent min. in 2 inches
TENSILE STRENGTH-ksi
SPECIFIED WALL
THICKNESS (inches)
ALLOY AND
TEMPER [3]
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 flattening, 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.
Aluminum Extrusion Manual
8-31
Section 8
Tolerances
Section
8
INTRODUCTION TO
GEOMETRIC
DIMENSIONING AND
TOLERANCING
Taken together, geometric dimensioning and tolerancing can be used to
specify the geometry or shape of an
extrusion on an engineering drawing.
It can be described as a modern technical language, which has uniform
meaning to all, and can vastly
improve communication in the cycle
from design to manufacture.
Terminology, however, varies in meaning according to the Geometric
Standard being used; this must be
taken into account in each case.
Geometric dimensioning and tolerancing, also referred to in colloquial
terms as geometrics, is based upon
sound engineering and manufacturing principles. It more readily captures the design intent by providing
designers and drafters better tools
with which to "say what they mean."
Hence, the people involved in manufacturing or production can more
clearly understand the design requirements. In practice, it becomes quite
evident that the basic "engineering"
(in terms of extruding, fixturing,
inspecting, etc.) is more logically consistent with the design intent when
geometric dimensioning and tolerancing is used. As one example,
functional gauging can be used to
facilitate the verification process and,
at the same time, protect design
intent. Geometric dimensioning and
tolerancing is also rapidly becoming a
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 management tool; it assists productivity, quality, and economics in producing and
marketing products around the
world.
RATIONALE OF
GEOMETRIC
DIMENSIONING AND
TOLERANCING
Geometric dimensioning and tolerancing builds upon previously established drawing practices. It adds,
however, a new dimension to drawing
skills in defining the part and its features, beyond the capabilities of the
older methods.
It is sometimes effective to consider
the technical benefits of geometric
dimensioning and tolerancing by
examining and analyzing a drawing
without such techniques used,
putting the interpretation of such a
drawing to the test of clarity. Have
the requirements of such a part been
adequately stated? Can it be produced with the clearest understanding? Geometric dimensioning and
tolerancing offers that clarity.
Often an engineer is concerned
about fit and function. With many
standard tolerances this may become
a concern. Geometric tolerancing is
structured to better control parts in a
fit-and-function relationship.
Aluminum Extrusion Manual
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
Note: Tolerances used within the
following examples are purely illustrative and may not reflect the standard
tolerances used by the aluminum
extrusion industry.
THE FEATURE CONTROL
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.
ANGULARITY
PERPENDICULARITY
PARALLELISM
CONCENTRICITY
CIRCULARITY
PROFILE OF A LINE
PROFILE OF A SURFACE
DIAMETER
DATUM FEATURE
A
MAXIMUM MATERIAL
CONDITION (MMC)
M
REGARDLESS OF FEATURE
SIZE (RFS)
S
LEAST MATERIAL
CONDITION (LMC)
L
TANGENT PLANE
T
A
or
This feature is to be in:
“POSITION”
WITHIN
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
Aluminum Extrusion Manual
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
;;
;;
A
-ATheoretically 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 perform 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.
Aluminum Extrusion Manual
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 surface 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
on
r
F
Aluminum Extrusion Manual
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
Profile of a Surface
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.
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.
,
S
or
L
not allowed
0.006
Never a datum reference
;;
;;;;
;;
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
Aluminum Extrusion Manual
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
0.006
Never a datum reference
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
Aluminum Extrusion Manual
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
Profile of
a Surface
Total Runout
A B
M
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
0.010 A B
0.010 A
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
Datum reference required
(minimum of one)
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
Required when the feature
and the datum feature are
both cylindrical
A
M
or L
S
is implied per Rule #2 (since 1994)
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
Profile of
a Surface
Total Runout
0.010 A B
M
A B
0.010 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
Datum reference required
(minimum of one)
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
Profile of
a Surface
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
Aluminum Extrusion Manual
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
Gauge Block
Aluminum Extrusion Manual
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
is implied per Rule #2
(since 1994)
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.
Aluminum Extrusion Manual
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
8-52
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.
Aluminum Extrusion Manual
8-53
projected tolerance zone —- A projected
tolerance zone is a tolerance zone
applied to a hole in which a pin, stud,
screw, or bolt, etc. is to be inserted. It
controls the perpendicularity of the hole
to the extent of the projection from the
hole and as it relates to the mating part
clearance. The projected tolerance zone
extends above the surface of the part to
the functional length of the pin, screw,
etc., relative to its assembly with the
mating part.
squareness —- See perpendicularity.
regardless of feature size (RFS) —- This is
the condition where the tolerance of
form, runout, or location must be met
irrespective of where the feature lies within its size tolerance.
transition fit —- A transition fit is one having limits of size so
prescribed that either a clearance or an interference may result
when mating parts are assembled.
roundness —- See circularity.
runout —- Runout is the composite
deviation from the desired form of a part
surface of revolution during full rotation
(360 degrees) of the part on a datum
axis. Runout tolerance may be circular
or total.
runout tolerance —- Runout tolerance
states how far an actual surface or feature
is permitted to deviate from the desired
form implied by the drawing during full
rotation of the part on a datum axis.
There are two types of runout: circular
runout and total runout.
size tolerance —- A size tolerance states
how far individual features may vary from
the desired size. Size tolerances are
specified with either unilateral, bilateral,
or limit tolerancing methods.
specified datum —- A specified datum is a
surface or feature identified with a datum
feature symbol.
straightness —- Straightness is a condition where an element of
a surface or an axis is a straight line.
symmetry —- Symmetry is a condition in which a feature (or
features) is (are) symmetrically disposed about the center plane
of a datum feature.
tolerance —- A tolerance is the total amount by which a specific
dimension may vary; thus, the tolerance is the difference
between limits.
true position —- True position is a term used to describe the
perfect (exact) location of a point, line, or plane of a feature in
relationship with a datum reference or other feature.
total indicator reading (TIR) (see also FIR and FIM) —- Total
indicator reading is the full indicator reading observed with the
dial indicator in contact with the part feature surface during one
full revolution of the part about its datum axis. Total indicator
reading also refers to the total indicator reading observed while
in traverse over a fixed noncircular shape. Use of the international term, FIM (which, see), is recommended.
total runout —- Total runout is the simultaneous composite
control of all elements of a surface at all circular and profile
measuring positions as the part is rotated through 360 degrees.
unilateral tolerance —- A unilateral tolerance is a tolerance in
which variation is permitted only in one direction from the
specified dimension, e.g., 1.400 + .000 - .005.
virtual condition —- Virtual condition of a feature is the collective effect of size, form, and location error that must be considered in determining the fit or clearance between mating parts or
features. It is a derived size generated from the profile variation
permitted by the specified tolerances. It represents the most
extreme condition of assembly at MMC.
Section 8
Tolerances
8-54