prEN 755-8

• Abstract:

  This document specifies the tolerances on dimensions and form for aluminium and aluminium alloy extruded porthole 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.; The temper designations used in this part are according to EN 515.; This document only applies to tube produced by the tube porthole/bridge method.; This document does not apply to:; — extruded tubes produced by the seamless, die/mandrel method (EN 755-7);; — tubes delivered in coils (EN 13957);; — coiled tubes cut to length (EN 13957).; Figure 1 — Round tube; Figure 2 — Circumscribing circle for other than round tube

• Status: Not Published
• Publication Date: 14-Dec-2027
• ICS: 77.150.10 - Aluminium products
• Technical Committee: CEN/TC 132 - Aluminium and aluminium alloys
• Drafting Committee: WG 35 - Extruded products
• Current Stage: 4020 - Submission to enquiry - Enquiry
• Start Date: 20-Aug-2026
• Due Date: 02-Sep-2026
• Completion Date: 20-Aug-2026
• Ref Project: oSIST prEN 755-8:2026 - Aluminium and aluminium alloys - Extruded rod/bar, tube and profiles - Part 8: Porthole tubes, tolerances on dimensions and form

• Revises: EN 755-8:2016 - Aluminium and aluminium alloys - Extruded rod/bar, tube and profiles - Part 8: Porthole tubes, tolerances on dimensions and form
• Effective Date: 15-Oct-2025

prEN 755-8 is a CEN draft European Standard for aluminium and aluminium alloy extruded porthole tubes. It specifies dimensional and form tolerances for straight-length tubes made by the tube porthole/bridge method, so manufacturers, purchasers and inspectors can specify, check and accept the product against the same limits.

What does prEN 755-8 specify?

prEN 755-8 specifies tolerances on dimensions and form for extruded porthole tubes in defined size ranges. It applies to round tube with an outside diameter (OD) from 8 mm to 450 mm, and to other than round tube within a circumscribing circle (CD) from 10 mm to 350 mm.

The document applies only to tube produced by the tube porthole/bridge method and supplied in straight lengths. It excludes seamless, die/mandrel tubes, tubes delivered in coils, and coiled tubes cut to length.

Annex	What it covers
Annex A, informative	Wall thickness variation (eccentricity) for round tube, including how to interpret OD × t, ID × t and OD × ID orders

The document is organized into Scope, Normative references, Terms and definitions, Alloy groups, tolerances on dimensions, tolerances on form, and Annex A.

What are the key requirements of prEN 755-8?

prEN 755-8 sets the dimensional and form tolerances that must be agreed and checked for porthole tube orders. The main practical point is that the buyer has to state the dimensions in a way that matches the tolerance method used by the standard.

Alloy groups and ordering basis

Clause 4 divides alloys into Group I and Group II because different alloys are more or less difficult to manufacture. For alloys outside the listed groups, the group must be agreed between supplier and purchaser. In practice, this grouping affects which tolerance table applies.

Dimensional tolerances

Clause 5.1 says that when OD, ID and wall thickness (t) are all specified, tolerances apply to only two of them, not all three. That means an order must be written carefully so the supplier knows which dimensions are controlling.

Clause 5.2 defines round-tube diameter tolerances, including mean diameter and the maximum deviation at any point, which includes ovality. If an order is unclear, the diameter tolerance is interpreted as inclusive of ovality unless the purchaser asks for both mean diameter and inclusive-of-ovality values.

Clause 5.3 gives the width, depth or width across flats tolerances for square, rectangular, hexagonal and octagonal tube. These depend on CD size and alloy group, so the declared tube shape and alloy group matter directly to acceptance.

Wall thickness, length and ends

Clause 5.4 sets wall thickness variation, also called eccentricity, separately for round tube and other than round tube. For round tube, the meaning depends on whether the tube is ordered as OD × t, ID × t or OD × ID; Annex A explains how to read those cases.

Clause 5.5 covers fixed length and random length. If fixed lengths are required, they must be stated on the order document, because the length tolerance and the delivery basis are linked.

Clause 5.6 limits the squareness of cut ends to half of the fixed-length tolerance range. In practice, that gives a simple check for whether the cut end is acceptable after trimming.

Form tolerances

Clause 6 covers straightness, convexity-concavity, twist, angularity, corner and fillet radii, and dents. These are the checks that prevent tubes from being rejected later because they do not fit, assemble or appear as required.

Clause 6.2 gives straightness measurement on a horizontal base plate under the tube’s own mass. Clause 6.3 and 6.4 give the measurement approach for convexity-concavity and twist. Clause 6.5 covers squareness for square and rectangular tubes, while the angular deviation of hexagonal and octagonal tubes is included in the width across flats tolerances. Clause 6.6 allows small corner and fillet rounding unless the drawing says otherwise. Clause 6.7 treats dent depth as an agreed requirement for applications where surface damage matters.

What terms does prEN 755-8 define?

prEN 755-8 uses a small set of working terms that matter for specification and inspection.

• OD - outside diameter, the external round size used for round tube orders and checks.
• ID - inside diameter, the internal round size used when tube is ordered from the bore side.
• CD - circumscribing circle, the circle that encloses a non-round section for size limits and tolerances.
• t - wall thickness, the tube wall dimension used with OD, ID or OD × ID ordering.
• Eccentricity - wall thickness variation around the tube circumference, which shows whether the wall is uniform.
• Straightness - deviation from a straight line when the tube is measured on a base plate.
• Twist - rotation of the tube along its length, measured as a form deviation.
• Temper - the material condition designation used with aluminium alloys, according to EN 515.

Who uses prEN 755-8?

prEN 755-8 is used by aluminium extrusion suppliers, purchasers, quality control teams and inspection laboratories that need a common way to specify and verify porthole tube dimensions and form. It is relevant for ordering, incoming inspection, production checks and acceptance decisions for straight-length tubes.

What changed in prEN 755-8 from the previous edition?

prEN 755-8 will supersede EN 755-8:2016. The draft states these technical changes:

• the alloy list was removed from Clause 1 and moved to a new Table 1;
• a new Clause 4 on alloy groups was added, with later clauses renumbered;
• a new Table 1 on alloy groups was added, with later tables renumbered;
• several alloys were added, including EN AW-1070A, EN AW-3102, EN AW-6106, EN AW-6360, EN AW-6014, EN AW-6262A, EN AW-6023, EN AW-6012, EN AW-7021, EN AW-7049A and EN AW-6026;
• a new footnote was added to Table 2;
• Table 4 was completely reworked.

Which standards are used with prEN 755-8?

Standard	What it contributes
EN 755-1:2016	Inspection and delivery conditions referenced as indispensable for application
EN 515	Temper designations used for aluminium and aluminium alloys
EN 755-7	Seamless tube tolerances, for the tube type excluded from this part
EN 13957	Coiled extruded round tube specification, for coiled tube excluded from this part

What does the prEN 755-8 document contain?

prEN 755-8 contains tolerance tables for diameter, width, wall thickness, fixed length, straightness, convexity-concavity, twist, squareness and corner radii. It also includes figures for the measurement of roundness-related dimensions and form checks, so users can measure the same way.

Annex A gives guidance on wall thickness variation for round tube and explains how the stated dimensions change the way eccentricity is interpreted. It is useful when an order is written as OD × t, ID × t or OD × ID, because the tolerance basis changes with the order format.

SLOVENSKI STANDARD
01-oktober-2026
Aluminij in aluminijeve zlitine - Iztiskane palice/drogovi, cevi in profili - 8. del: Z
večdelnimi matricami iztiskane cevi, tolerance mer in oblike
Aluminium and aluminium alloys - Extruded rod/bar, tube and profiles - Part 8: Porthole
tubes, tolerances on dimensions and form
Aluminium und Aluminiumlegierungen - Stranggepresste Stangen, Rohre und Profile -
Teil 8: Mit Kammerwerkzeug stranggepresste Rohre, Grenzabmaße und Formtoleranzen
Aluminium et alliages d'aluminium - Barres, tubes et profilés filés - Partie 8 : Tubes filés
porthole, tolérances sur dimensions et forme
Ta slovenski standard je istoveten z: prEN 755-8
ICS:
77.150.10 Aluminijski izdelki Aluminium products
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

DRAFT
EUROPEAN STANDARD
NORME EUROPÉENNE
EUROPÄISCHE NORM
August 2026
ICS 77.150.10 Will supersede EN 755-8:2016
English Version
Aluminium and aluminium alloys - Extruded rod/bar, tube
and profiles - Part 8: Porthole tubes, tolerances on
dimensions and form
Aluminium et alliages d'aluminium - Barres, tubes et Aluminium und Aluminiumlegierungen -
profilés filés - Partie 8 : Tubes filés porthole, tolérances Stranggepresste Stangen, Rohre und Profile - Teil 8:
sur dimensions et forme Mit Kammerwerkzeug stranggepresste Rohre,
Grenzabmaße und Formtoleranzen
This draft European Standard is submitted to CEN members for enquiry. It has been drawn up by the Technical Committee
CEN/TC 132.
If this draft becomes a European Standard, 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.

This draft European Standard was established by CEN 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, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway,
Poland, Portugal, Republic of North Macedonia, Romania, Serbia, Slovakia, Slovenia, Spain, Sweden, Switzerland, Türkiye and
United Kingdom.
Recipients of this draft are invited to submit, with their comments, notification of any relevant patent rights of which they are
aware and to provide supporting documentation.

Warning : This document is not a European Standard. It is distributed for review and comments. It is subject to change without
notice and shall not be referred to as a European Standard.

EUROPEAN COMMITTEE FOR STANDARDIZATION
COMITÉ EUROPÉEN DE NORMALISATION

EUROPÄISCHES KOMITEE FÜR NORMUNG

CEN-CENELEC Management Centre: Rue de la Science 23, B-1040 Brussels
© 2026 CEN All rights of exploitation in any form and by any means reserved Ref. No. prEN 755-8:2026 E
worldwide for CEN national Members.

Contents Page
European foreword . 3
1 Scope . 4
2 Normative references . 5
3 Terms and definitions . 5
4 Alloy groups . 5
5 Tolerances on dimensions . 5
5.1 General . 5
5.2 Diameter - Round tube . 5
5.3 Width, depth or width across flats - squares, rectangles, hexagons, octagons . 7
5.4 Wall thickness variation (eccentricity) . 7
5.5 Length . 9
5.6 Squareness of cut ends . 9
6 Tolerances on form . 9
6.1 General . 9
6.2 Straightness . 9
6.3 Convexity-Concavity . 10
6.4 Twist . 11
6.5 Angularity . 12
6.6 Corner and fillet radii . 13
6.7 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
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
European foreword
This document (prEN 755-8:2026) has been prepared by Technical Committee CEN/TC 132 “Aluminium
and aluminium alloys”, the secretariat of which is held by AFNOR.
This document is currently submitted to the CEN Enquiry.
This document will supersede EN 755-8:2016.
— list of alloys deleted from Clause 1 and alloys moved to new Table 1;
— new Clause 4 Alloy groups, and subsequent clauses renumbered;
— new Table 1 Alloy groups, and subsequent tables renumbered;
— the following alloys have been added: EN AW-1070A, EN AW-3102, EN AW-6106, EN AW-6360,
EN AW-6014, EN AW-6262A, EN AW-6023, EN AW-6012, EN AW-7021, EN AW-7049A, EN AW-
6026;
— new footnote added to Table 2 (old Table 1);
— Table 4 (old Table 3) totally reworked.
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;
— 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.

1 Scope
This document specifies the tolerances on dimensions and form for aluminium and aluminium alloy
extruded porthole 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.
The temper designations used in this part are according to EN 515.
This document only applies to tube produced by the tube porthole/bridge method.
This document does not apply to:
— extruded tubes produced by the seamless, die/mandrel method (EN 755-7);
— tubes delivered in coils (EN 13957);
— coiled tubes cut to length (EN 13957).

Figure 1 — Round tube
Figure 2 — Circumscribing circle for other than round tube
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 Terms and definitions
No terms and definitions are listed in this document.
4 Alloy groups
For the purpose of this document, the alloys are distributed into two groups, Group I and Group II 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-1200, EN AW-1350, EN AW-1070,
EN AW-3003, EN AW-3103, EN AW-3102,
EN AW-5005, EN AW-5005A,
EN AW-6005, EN AW-6005A, EN AW-6008, EN AW-6065, EN AW-6101B,
EN AW-6014, EN AW-6060, EN AW-6063, EN AW-6063A, EN AW-6106,
EN AW-6360, EN AW-6463
Group II EN AW-5049, EN AW-5051A, EN AW-5052, EN AW-5251,
EN AW-6012, EN AW-6014, EN AW−6018, EN AW-6023, EN AW-6026,
EN AW-6061, EN AW-6065, EN AW-6081, EN AW-6082, EN AW-6110A,
EN AW-6182, EN AW-6261, EN AW-6262, EN AW-6262A, EN AW-6351,
EN AW-7003, EN AW-7005, EN AW-7020, EN AW-7021, EN AW-7108,
EN AW-7108A, EN AW-7049A
5 Tolerances on dimensions
5.1 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.
5.2 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.
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 i.e. 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
Maximum allowable deviation of diameter
(OD or ID)
Maximum allowable a
at any point from specified diameter
deviation of mean
Non-annealed
diameter from specified
Up to and Heat treated Annealed
Over g and non heat
diameter
c d e
including tube  tube
b
treated tube
f f f f
≥ 8 18 ±0,25 ±0,40 ±0,60 ±1,5
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
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 diam
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