October 2016

DIN EN 755-7
D
ICS 77.150.10 Supersedes
DIN EN 755­7:2009­07

Aluminium and aluminium alloys –

Extruded rod/bar, tube and profiles –
Part 7: Seamless tubes, tolerances on dimensions and form;
English version EN 755­7:2016,
English translation of DIN EN 755-7:2016-10

Aluminium und Aluminiumlegierungen –

Stranggepresste Stangen, Rohre und Profile –
Teil 7: Nahtlose Rohre, Grenzabmaße und Formtoleranzen;
Englische Fassung EN 755­7:2016,
Englische Übersetzung von DIN EN 755-7:2016-10
Aluminium et alliages d’aluminium –
Barres, tubes et profilés filés –
Partie 7: Tubes filés sur aiguille, tolérances sur dimensions et forme;
Version anglaise EN 755­7:2016,
Traduction anglaise de DIN EN 755-7:2016-10
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Document comprises 19 pages

Translation by DIN-Sprachendienst.
In case of doubt, the German-language original shall be considered authoritative.

© No part of this translation may be reproduced without prior permission of English price group 11
DIN Deutsches Institut für Normung e. V., Berlin. Beuth Verlag GmbH, 10772 Berlin, Germany,
has the exclusive right of sale for German Standards (DIN-Normen).
www.din.de
www.beuth.de
!%\nN"
09.16 2577543
 DIN EN 755-7:2016-10

A comma is used as the decimal marker.

National foreword
This document (EN 755-7:2016) has been prepared by Technical Committee CEN/TC 132 “Aluminium and
aluminium alloys” (Secretariat: AFNOR, France).

The responsible German body involved in its preparation was DIN-Normenausschuss Nichteisenmetalle (DIN
Standards Committee Nonferrous Metals), Working Committee NA 066-01-04 AA Strangpresserzeugnisse.

Amendments

This standard differs from DIN EN 755-7:2009-07 as follows:

a) a new Clause 2 “Normative references” has been included and the numbering of the paragraphs
following has been updated accordingly;

b) in Subclause 4.2 “Diameter — Round tube”, a correction has been made and paragraphs 2 and 4 have
been added.

Previous editions

DIN 9107: 1944-03, 1959-08, 1969-08, 1987-02

DIN EN 755-7: 1998-10, 2008-06, 2009-07
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 EUROPEAN STANDARD EN 755-7
NORME EUROPÉENNE
EUROPÄISCHE NORM June 2016

ICS 77.150.10 Supersedes EN 755-7:2008

English Version

Aluminium and aluminium alloys - Extruded rod/bar, tube

and profiles - Part 7: Seamless tubes, tolerances on
dimensions and form
Aluminium et alliages d'aluminium - Barres, tubes et Aluminium und Aluminiumlegierungen -
profilés filés - Partie 7 : Tubes filés sur aiguille, Stranggepresste Stangen, Rohre und Profile - Teil 7:
tolérances sur dimensions et forme Nahtlose Rohre, Grenzabmaße und Formtoleranzen

This European Standard was approved by CEN on 11 April 2016.

CEN members are bound to comply with the CEN/CENELEC Internal Regulations which stipulate the conditions for giving this
European Standard the status of a national standard without any alteration. Up-to-date lists and bibliographical references
concerning such national standards may be obtained on application to the CEN-CENELEC Management Centre or to any CEN
member.

This European Standard exists in three official versions (English, French, German). A version in any other language made by
translation under the responsibility of a CEN member into its own language and notified to the CEN-CENELEC Management
Centre has the same status as the official versions.

CEN members are the national standards bodies of Austria, Belgium, Bulgaria, Croatia, Cyprus, Czech Republic, Denmark, Estonia,
Finland, Former Yugoslav Republic of Macedonia, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania,
Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Romania, Slovakia, Slovenia, Spain, Sweden, Switzerland, Turkey and
United Kingdom.
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EUROPEAN COMMITTEE FOR STANDARDIZATION

COMITÉ EUROPÉEN DE NORMALISATION
EUROPÄISCHES KOMITEE FÜR NORMUNG

CEN-CENELEC Management Centre: Avenue Marnix 17, B-1000 Brussels

© 2016 CEN All rights of exploitation in any form and by any means reserved Ref. No. EN 755-7:2016 E
worldwide for CEN national Members.
 DIN EN 755-7:2016-10
EN 755-7:2016 (E)

Contents Page

European foreword....................................................................................................................................................... 3
1 Scope .................................................................................................................................................................... 4
2 Normative references .................................................................................................................................... 5
3 Alloy groups ...................................................................................................................................................... 5
4 Tolerances on dimensions ........................................................................................................................... 5
4.1 General ................................................................................................................................................................ 5
4.2 Diameter - Round tube .................................................................................................................................. 5
4.3 Width, depth or width across flats - squares, rectangles, hexagons, octagons ......................... 6
4.4 Wall thickness variation (eccentricity) ................................................................................................... 7
4.5 Length .................................................................................................................................................................. 8
4.6 Squareness of cut ends .................................................................................................................................. 9
5 Tolerances on form ........................................................................................................................................ 9
5.1 General ................................................................................................................................................................ 9
5.2 Straightness....................................................................................................................................................... 9
5.3 Convexity-Concavity .................................................................................................................................... 10
5.4 Twist ................................................................................................................................................................. 11
5.5 Angularity ....................................................................................................................................................... 12
5.6 Corner and fillet radii ................................................................................................................................. 13
5.7 Depth of dents for round tube ................................................................................................................. 14
Annex A (informative) Wall thickness variation (eccentricity) ................................................................. 15
A.1 General ............................................................................................................................................................. 15
A.2 Specifying round tube sizes and tolerances ....................................................................................... 15
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A.2.1 General ............................................................................................................................................................. 15

A.2.2 Wall thickness variation for tubes specified as OD × t or ID × t ................................................... 15
A.2.3 Wall thickness variation for tubes specified as OD × ID ................................................................. 16
Bibliography ................................................................................................................................................................. 17

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EN 755-7:2016 (E)

European foreword

This document (EN 755-7:2016) has been prepared by Technical Committee CEN/TC 132 “Aluminium
and aluminium alloys”, the secretariat of which is held by AFNOR.

This European Standard shall be given the status of a national standard, either by publication of an
identical text or by endorsement, at the latest by December 2016, and conflicting national standards
shall be withdrawn at the latest by December 2016.

Attention is drawn to the possibility that some of the elements of this document may be the subject of
patent rights. CEN [and/or CENELEC] shall not be held responsible for identifying any or all such patent
rights.

This document supersedes EN 755-7:2008.

The following technical modifications have been introduced during the revision:

— Subclause 4.2, Diameter - Round tube.

EN 755 comprises the following parts under the general title Aluminium and aluminium alloys —
Extruded rod/bar, tube and profiles:

— Part 1: Technical conditions for inspection and delivery;

— Part 2: Mechanical properties;

— Part 3: Round bars, tolerances on dimensions and form;

— Part 4: Square bars, tolerances on dimensions and form;

— Part 5: Rectangular bars, tolerances on dimensions and form;

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— Part 6: Hexagonal bars, tolerances on dimensions and form;

— Part 7: Seamless tubes, tolerances on dimensions and form;

— Part 8: Porthole tubes, tolerances on dimensions and form;

— Part 9: Profiles, tolerances on dimensions and form.

According to the CEN/CENELEC Internal Regulations, the national standards organizations of the
following countries are bound to implement this European Standard: Austria, Belgium, Bulgaria,
Croatia, Cyprus, Czech Republic, Denmark, Estonia, Finland, Former Yugoslav Republic of Macedonia,
France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta,
Netherlands, Norway, Poland, Portugal, Romania, Slovakia, Slovenia, Spain, Sweden, Switzerland,
Turkey and the United Kingdom.

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EN 755-7:2016 (E)

1 Scope
This European Standard specifies the tolerances on dimensions and form for aluminium and aluminium
alloy extruded seamless tubes with an outside diameter (OD) from 8 mm to 450 mm (round tube,
see Figure 1) or with a cross section contained within a circumscribing circle (CD) from 10 mm to
350 mm (other than round tube, see Figure 2), supplied in straight lengths.
This European Standard only applies to tube produced by the seamless die/mandrel method of
extrusion. This standard applies to extruded seamless tube for general engineering applications only.
The temper designations used in this part are according to EN 515.
This European Standard does not apply to:
— extruded tubes produced by porthole/bridge method (EN 755-8),

— tubes delivered in coils (EN 13957),

— coiled tubes cut to length (EN 13957).

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Figure 1 — Round tube

Figure 2 — Circumscribing circle for other than round tube

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2 Normative references
The following documents, in whole or in part, are normatively referenced in this document and are
indispensable for its application. For dated references, only the edition cited applies. For undated
references, the latest edition of the referenced document (including any amendments) applies.
EN 755-1:2016, Aluminium and aluminium alloys — Extruded rod/bar, tube and profiles — Part 1:
Technical conditions for inspection and delivery

3 Alloy groups
For the purposes of this European Standard, the alloys are distributed into two groups which
correspond to varying degrees of difficulty when manufacturing the products.
The division into group I and group II of the most commonly used general engineering alloys is
specified in Table 1. Grouping of other alloys is subject to agreement between supplier and purchaser.

Table 1 — Alloy groups

Group I EN AW-1050A, EN AW-1070A, EN AW-1200, EN AW-1350
EN AW-3102, EN AW-3003, EN AW-3103
EN AW-5005, EN AW-5005A
EN AW-6101A, EN AW-6101B, EN AW-6005, EN AW-6005A,
EN AW-6106, EN AW-6008 EN AW-6014, EN AW-6060, EN AW-6360, EN AW-6063,
EN AW-6063A, EN AW-6463
Group II EN AW-2007, EN AW-2011, EN AW-2011A, EN AW-2014,
EN AW-2014A, EN AW-2017A, EN AW-2024, EN AW-2030

EN AW-5019, EN AW-5049, EN AW-5051A, EN AW-5251, EN AW-5052,

EN AW-5154A, EN AW-5454, EN AW-5754, EN AW-5083, EN AW-5086
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EN AW-6110A, EN AW-6012, EN AW-6018, EN AW-6023, EN AW-6351, EN AW-6061,

EN AW-6261, EN AW-6262, EN AW-6081, EN AW-6082
EN AW-7003, EN AW-7005, EN AW-7108, EN AW-7108A, EN AW-7020, EN AW-7021,
EN AW-7022, EN AW-7049A, EN AW-7075

4 Tolerances on dimensions

4.1 General

When outside diameter OD, inside diameter ID, and wall thickness t, (or their equivalent dimensions in
other than round tube) are all specified, standard tolerances shall apply to any two of these dimensions,
but not to all three. As a result, the purchaser shall only state two nominal dimensions on any given
order.
4.2 Diameter - Round tube

Mean diameter is defined as the average of two diameter measurements taken at right angles to each
other at any position along the length.

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The maximum allowable deviation of diameter at any point from the specified diameter is the maximum
difference measured at any point along the length of the tube ie it is inclusive of any ovality in the cross
section.
The tolerances on diameter are specified in Table 2.
As detailed in EN 755-1:2016, Clause 4, if the original order does not make clear the nature of the
diameter tolerances required, the supplier shall interpret them as inclusive of any ovality (i.e. maximum
allowable deviation at any point from the specified diameter in Table 2). However, the diameter
tolerances may be expressed as both mean and inclusive of ovality if this is specifically requested by the
purchaser.

Table 2 — Tolerances on diameter for round tube

Dimensions in millimetres
Tolerance on diameter
Diameter
(OD or ID) Maximum allowable deviation of diameter at
Maximum allowable deviation any point from specified diameter a
of mean diameter from Tempers O,
Up to and specified diameter d Tempers F and Heat treated
Over H111 and
including H112 tube b
Tx510

≥8 18 ±0,25 c ±0,40 c ±0,60 c ±1,5 c

18 30 ±0,30 ±0,50 ±0,70 ±1,8
30 50 ±0,35 ±0,60 ±0,90 ±2,2
50 80 ±0,40 ±0,70 ±1,1 ±2,6
80 120 ±0,60 ±0,90 ±1,4 ±3,6
120 200 ±0,90 ±1,4 ±2,0 ±5,0
200 350 ±1,4 ±1,9 ±3,0 ±7,6
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350 450 ±1,9 ±2,8 ±4,0 ±10,0

a Not applicable to tubes having a wall thickness less than 2,5 % of the specified outside diameter. The tolerance for
tubes with wall thickness less than 2,5 % of the specified outside diameter shall be determined by multiplying the
applicable tolerance as follows:
— wall thickness over 2,0 % up to and including 2,5 % of outside diameter: 1,5 × tolerance;
— wall thickness over 1,5 % up to and including 2,0 % of outside diameter: 2,0 × tolerance;
— wall thickness over 1,0 % up to and including 1,5 % of outside diameter: 3,0 × tolerance;
— wall thickness over 0,5 % up to and including 1,0 % of outside diameter: 4,0 × tolerance.
b Applies to all alloys in T4, T5, T6, T64, T66 and Tx511 tempers.
c This tolerance applies for outside diameter only, i.e. tube in this size range can only be specified as “Outside
Diameter x Wall Thickness”.
d Not applicable to Tx510 or Tx511 tempers.

4.3 Width, depth or width across flats - squares, rectangles, hexagons, octagons

The tolerances on width, depth or width across flats are specified in Table 3.

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Table 3 — Tolerances on width, depth or width across flats

Dimensions in millimetres
Width, depth or Tolerances on width, depth or width across flats a, b
width
across flats CD ≤ 100 100 < CD ≤ 200 200 < CD ≤ 300 300 < CD ≤ 350

Alloy Alloy Alloy Alloy Alloy Alloy Alloy

Alloy
Up to and
Over group group group group group group group group
including
I
I II I II I II II
- 10 ±0,25 ±0,40 ±0,30 ±0,50 ±0,35 ±0,55 ±0,40 ±0,60
10 25 ±0,30 ±0,50 ±0,40 ±0,70 ±0,50 ±0,80 ±0,60 ±0,90
25 50 ±0,50 ±0,80 ±0,60 ±0,90 ±0,80 ±1,0 ±0,90 ±1,2
50 100 ±0,70 ±1,0 ±0,90 ±1,2 ±1,1 ±1,3 ±1,3 ±1,6
100 150 - - ±1,1 ±1,5 ±1,3 ±1,7 ±1,5 ±1,8
150 200 - - ±1,3 ±1,9 ±1,5 ±2,2 ±1,8 ±2,4
200 300 - - - - ±1,7 ±2,5 ±2,1 ±2,8
300 350 - - - - - - ±2,8 ±3,5
a Not applicable to tubes having a wall thickness less than 2,5 % of the specified outside width, depth or width across flats.
The tolerance for tubes with wall thickness less than 2,5 % of the specified width, depth or width across flats shall be
determined by multiplying the applicable tolerance as follows:
— wall thickness over 2,0 % up to and including 2,5 % of outside parameter: 1,5 × tolerance;
— wall thickness over 1,5 % up to and including 2,0 % of outside parameter: 2,0 × tolerance;
— wall thickness over 1,0 % up to and including 1,5 % of outside parameter: 3,0 × tolerance;
— wall thickness over 0,5 % up to and including 1,0 % of outside parameter: 4,0 × tolerance.
b These tolerances do not apply to tempers O and Tx510. For these tempers the tolerances shall be subject to agreement
between supplier and purchaser.
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4.4 Wall thickness variation (eccentricity)

The tolerances on wall thickness variation (eccentricity) are specified in Table 4 for round tubes and in
Table 5 for other than round tubes.

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Table 4 — Tolerances on wall thickness variation (eccentricity) for round tubes

Nominal wall thickness

t Tolerance on of wall thickness
mm
variation (eccentricity)
%a
Over Up to and including

- 3 ±10
3 5 ±9
5 - ±8
NOTE Round tube dimensions can be expressed in three different ways i.e. outside diameter
(OD) × wall thickness (t), inside diameter (ID) × t (where t is the nominal wall thickness) and OD × ID.
Depending of the way of ordering the tube the values in Table 4 should be understood as follows
(see Annex A for further explanation):
— for tubes specified as OD x t or ID x t the values are allowable variation at any point;
— for tubes specified as OD x ID the above values are allowable variation from the calculated mean
wall thickness.
a For OD greater than 150 mm together with and OD/t ratio of more than 10, the
tolerance on wall thickness variation shall be subjected to agreement between supplier and
purchaser.

Table 5 — Tolerances on wall thickness for other than round tubes

Dimensions in millimetres

Nominal wall thickness Tolerances on wall thickness for circumscribing circle CD

t CD ≤ 100 100 < CD ≤ 300 300 < CD ≤ 350
Up to and Alloy Alloy Alloy Alloy Alloy Alloy
Over
including group I group II group I group II group I group II
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≥ 0,5 1,5 ±0,25 ±0,35 ±0,35 ±0,50 - -

1,5 3 ±0,30 ±0,45 ±0,50 ±0,65 ±0,75 ±0,90
3 6 ±0,50 ±0,60 ±0,75 ±0,90 ±1,0 ±1,2
6 10 ±0,75 ±1,0 ±1,0 ±1,3 ±1,2 ±1,5
10 15 ±1,0 ±1,3 ±1,2 ±1,7 ±1,5 ±1,9
15 20 ±1,5 ±1,9 ±1,9 ±2,2 ±2,0 ±2,5
20 30 ±1,9 ±2,2 ±2,2 ±2,7 ±2,5 ±3,1
30 40 - - ±2,5 - ±2,7 -

4.5 Length

If fixed lengths are to be supplied, this shall be stated on the order. The maximum allowable tolerances
on fixed length are specified in Table 6.

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Table 6 — Tolerances on fixed length

Dimensions in millimetres

Outside diameter or
diameter of Tolerances on fixed length
circumscribing circle

Up to and
Over L ≤ 2 000 2 000 < L ≤ 5 000 5 000 < L ≤ 10 000 10 000 < L ≤ 15 000 15 000 < L ≤ 25 000
including

+5 +7 +10 +16 +22

≥8 100
0 0 0 0 0

+7 +9 +12 +18 +24

100 200
0 0 0 0 0

+8 +11 +14 +20 +28

200 450
0 0 0 0 0

If no fixed length is specified in the order, seamless tubes may be delivered in random lengths. The
length range and the tolerances on the random length shall be subject to agreement between supplier
and purchaser.
4.6 Squareness of cut ends

The squareness of cut ends shall be within half of the fixed-length tolerance range specified in Table 6
for both fixed and random lengths (e.g. for a fixed-length tolerance of +10
0 mm, the squareness of cut
ends shall be within 5 mm).

5 Tolerances on form
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5.1 General

Tolerances on form for O and Tx510 tempers shall be subject to agreement between supplier and
purchaser.
5.2 Straightness

Deviations from straightness, hs and ht, shall be measured as shown in Figure 3 with the tube placed on
a horizontal baseplate so that its mass decreases the deviation.
The straightness tolerances of round tubes are specified in Table 7 (The straightness tolerance ht
applies to the whole length, e.g. for a length of 6 m the maximum deviation from straightness ht is the
value given in the table multiplied by 6 m).
The straightness tolerance ht of other than round tubes shall not exceed 1,5 mm/m length. Local
deviations hs from straightness shall not exceed 0,6 mm/300 mm length.

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Key
1 base plate
2 straight edge

Figure 3 — Measurement of the deviation from straightness

Table 7 — Straightness tolerances of round tube

Dimensions in millimetres
Maximum deviation
Outside diameter
from straightness Maximum localized kink
per metre length in any 300 mm portion
Up to and ht/length hs
Over
including mm/m
≥8 150 1,5 0,8
150 250 2,5 1,3
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250 450 3,5 1,8

The straightness tolerances for tubes having a wall thickness less than 1,5 % of the specified outside
diameter shall be subject to agreement between supplier and purchaser.
5.3 Convexity-Concavity

The convexity-concavity of other than round tube shall be measured as shown in Figure 4. The
convexity-concavity tolerances are specified in Table 8.

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EN 755-7:2016 (E)

Key
1 straight edge
2 base plate

Figure 4 — Measurement of convexity–concavity

Table 8 — Convexity-Concavity tolerances

Dimensions in millimetres
Width W Maximum allowable deviation f
Up to and
Over Wall thickness ≤ 5 Wall thickness > 5
including
- 30 0,30 0,20
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30 60 0,40 0,30
60 100 0,60 0,40
100 150 0,90 0,60
150 200 1,2 0,80
200 350 1,8 1,2

5.4 Twist

Twist T shall be measured as shown in Figure 5 by placing the tube on a flat base plate, the tube resting
under its own mass and measuring the maximum distance at any point along the length between the
bottom surface of the tube and the base plate surface.
Twist tolerances are specified in Table 9 as a function of the width W and the length L of the tube.

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Key
1 base plate

Figure 5 — Measurement of twist

Table 9 — Twist tolerances

Dimensions in millimetres
Twist tolerance T
Width W
On total tube length L
per 1 000 mm
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Up to and of length a up to and

Over over 6 000
including including 6 000
≥ 10 30 1,2 2,5 3,0
30 50 1,5 3,0 4,0
50 100 2,0 3,5 5,0
100 200 2,5 5,0 7,0
200 350 2,5 6,0 8,0
a Twist tolerances for lengths less than 1 000 mm shall be subject to agreement between supplier
and purchaser.

5.5 Angularity

The deviation from square of square and rectangular tubes shall be measured as shown in Figure 6. The
maximum allowable deviation from square is specified in Table 10 as a function of tube depth B. In case
of rectangular tubes, the tolerance on squareness shall apply to the shorter side of the tube.
The maximum allowable deviation in an angle other than a right angle (hexagonal tubes, octagonal
tubes) shall be included within the width across flats tolerances, see Table 3.

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Figure 6 — Measurement of deviation from square

Table 10 — Squareness tolerances for square and rectangular tubes

Dimensions in millimetres
Depth
B Maximum allowable deviation Z
from square
Over Up to and including
- 30 0,4
30 50 0,7
50 80 1,0
80 120 1,4
120 180 2,0
180 240 2,6
240 350 3,1
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5.6 Corner and fillet radii

Sharp corners and fillet radii may be slightly rounded unless otherwise indicated on the drawing. The
maximum allowable radii are specified in Table 11.
When corner or fillet radius is specified, the maximum allowable deviation from the nominal value is
specified in Table 12.

Table 11 — Maximum allowable corner and fillet radii

Dimensions in millimetres
Maximum allowable corner and fillet radii
Wall thickness
Alloy group I Alloy group II a
≤5 0,6 0,8
>5 1,0 1,5
a These tolerances only apply to 6xxx series alloys in group II. The maximum allowable radii for the other alloys in group II
shall be subject to agreement between supplier and purchaser.

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Table 12 — Maximum allowable deviation from specified corner and fillet radii

Specified radius
Maximum allowable deviation from nominal value of the radius
mm

≤5 ±0,5 mm
>5 ±10 %

5.7 Depth of dents for round tube

It is recognized in certain applications that the depth of surface dents can be an important factor
particularly for round tube with large diameter to wall thickness ratios. In such cases, the maximum
allowable depth of dents shall be subject to agreement between supplier and purchaser.
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Annex A
(informative)

Wall thickness variation (eccentricity)

A.1 General
Wall thickness variation tolerances for round tube can be the source of a lot of confusion. In particular
as to whether quoted values are based on the nominal or mean wall thickness. This present section is
included in the standard to provide some guidelines as to when each of these possibilities is more
appropriate.

A.2 Specifying round tube sizes and tolerances

A.2.1 General

It is evident that round tube dimensions can be expressed in three different ways i.e. outside diameter
(OD) × wall thickness (t), inside diameter (ID) × t (where t is the nominal wall thickness) and OD × ID.
Since all three dimensions interact in any given size tube, it is only possible to apply tolerances to any
two of the parameters depending on which are the most important for the application of the tube in
question. The choice of the dimensional parameters has a very significant effect on how the wall
thickness variation is expressed.
The method of measuring wall thickness t is the same whether the given tube is specified as OD × t,
ID × t or OD × ID and is shown in Figure A.1. The tube wall thickness is measured around the
circumference of the tube and the maximum (tmax) and minimum (tmin) values established.
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Figure A.1 — Minimum and maximum values of the tube wall thickness

A.2.2 Wall thickness variation for tubes specified as OD × t or ID × t

For tube that is specified as either OD × t or ID × t, the nominal wall thickness t can be used as the basis
for calculating and expressing the wall thickness variation tolerance. The tolerance can be expressed as
the difference (in millimetres) between the maximum and minimum values permissible for the tube i.e.
at any point, maximum wall thickness variation, deviation or concentricity:

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EN 755-7:2016 (E)

t max − t min in mm (A.1)

Alternatively, the difference can be expressed as a percentage of the nominal wall thickness which is
normally divided by two to give a plus and minus tolerance. This percentage is normally expressed on
a ± basis as follows:
t max − t min
× 100 % (A.2)
2t

A.2.3 Wall thickness variation for tubes specified as OD × ID

In the case of tubes specified as OD × ID, there is no nominal wall thickness available to allow the same
method of wall thickness variation calculation as that described in A.2.2. As a result, it is necessary to
use the measured tmax and tmin values to give a wall thickness difference which is then used to calculate a
percentage of the mean wall thickness.
t max − t min
× 100 % (A.3)
(t max + t min ) / 2
This value may then be divided by two to give a plus/ minus value for the tolerance.
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EN 755-7:2016 (E)

Bibliography

[1] EN 515, Aluminium and aluminium alloys — Wrought products — Temper designations

[2] EN 755-8, Aluminium and aluminium alloys — Extruded rod/bar, tube and profiles — Part 8:
Porthole tubes, tolerances on dimensions and form

[3] EN 13957, Aluminium and aluminium alloys — Extruded round, coiled tube for general
applications — Specification
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