ISO 12573:2010

INTERNATIONAL ISO
STANDARD 12573
First edition
2010-09-15
Aircraft — Tubing tolerances — Inch
series
Aéronefs — Tolérances de tuyauterie — Série en inches

Reference number
©
ISO 2010
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ii © ISO 2010 – All rights reserved

Contents Page
Foreword .iv
Introduction.v
1 Scope.1
2 Normative references.1
3 Terms and definitions .1
4 Tubes in titanium and titanium alloys .4
4.1 Dimensions .4
4.2 Tolerances.4
5 Tubes in aluminium alloys.5
5.1 Dimensions .5
5.2 Tolerances.6
6 Tubes in corrosion resistant steel (CRES) .7
6.1 Dimensions .7
6.2 Tolerances.7
7 Tubes in nickel alloys .8
7.1 Dimensions .8
7.2 Tolerances.9

Foreword
ISO (the International Organization for Standardization) is a worldwide federation of national standards bodies
(ISO member bodies). The work of preparing International Standards is normally carried out through ISO
technical committees. Each member body interested in a subject for which a technical committee has been
established has the right to be represented on that committee. International organizations, governmental and
non-governmental, in liaison with ISO, also take part in the work. ISO collaborates closely with the
International Electrotechnical Commission (IEC) on all matters of electrotechnical standardization.
International Standards are drafted in accordance with the rules given in the ISO/IEC Directives, Part 2.
The main task of technical committees is to prepare International Standards. Draft International Standards
adopted by the technical committees are circulated to the member bodies for voting. Publication as an
International Standard requires approval by at least 75 % of the member bodies casting a vote.
Attention is drawn to the possibility that some of the elements of this document may be the subject of patent
rights. ISO shall not be held responsible for identifying any or all such patent rights.
ISO 12573 was prepared by Technical Committee ISO/TC 20, Aircraft and space vehicles, Subcommittee
SC 10, Aerospace fluid systems and components.

iv © ISO 2010 – All rights reserved

Introduction
The purpose of this International Standard is to harmonize the dimensional tolerances used in the preparation
of aerospace tubing. It is intended that future aerospace tubing standards refer to this International Standard
for the purpose of defining dimensional tolerances.
International Standards use the International System of units (SI); however, large segments of the aerospace
industry make use of other measurement systems as a matter of common working practice. The title of this
International Standard (“Inch series”) reflects the fact that nominal sizes (see definition 3.1), which are in
common use in the aerospace industry, were originally defined in terms of fractional inches.
Although tube sizes were originally defined (and are frequently cited) using non-SI units, all dimensions used
in this International Standard are given in SI units, with inch units also indicated for the convenience of the
user.
The decimal sign used in International Standards is the comma (“,”); however, the comma is not used in
common working practice for inch dimensions. Therefore, in common with many other aerospace standards,
the decimal point is used in this International Standard when providing dimensions in inches.
NOTE The use of non-SI units and the decimal point in this International Standard does not constitute general
acceptance of measurement systems other than SI within International Standards.

INTERNATIONAL STANDARD ISO 12573:2010(E)

Aircraft — Tubing tolerances — Inch series
1 Scope
This International Standard specifies the dimensional tolerances to be applied to round section inch series
tubing used in aircraft.
2 Normative references
The following referenced documents are indispensable for the application of this document. For dated
references, only the edition cited applies. For undated references, the latest edition of the referenced
document (including any amendments) applies.
ISO 8575, Aerospace — Fluid systems — Hydraulic system tubing
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
3.1
nominal size
dash number
d
N
non-dimensional characteristic which identifies the size of the parts of a fluid system
NOTE For a tube, the nominal size corresponds to the nominal value of the outside diameter, expressed in sixteenths
of an inch (1,59 mm).
EXAMPLE −04 corresponds to 4/16 in = 0.250 in = 6,35 mm.
3.2
outside diameter
d
distance between any two points at 180° to each other around the outside of a single section across the tube
NOTE Unless otherwise specified, the limits on the outside diameter therefore include all allowances for ovality (lack
of circularity).
See Figure 1.
Key
d outside diameter
d inside diameter
t wall thickness
Figure 1 — Outside diameter, inside diameter and wall thickness
3.3
mean outside diameter
arithmetic mean of two measurements of the outside diameter, taken at right angles to each other around a
single section across the tube
NOTE Where a mean outside diameter is specified, a limitation on ovality is also specified.
See Figure 2.
Key
d maximum outside diameter
1,max
d minimum outside diameter
1,min
dd−
1,max 1,min
mean outside diameter:
ovality: dd−
1,max 1,min
Figure 2 — Mean outside diameter and ovality
3.4
inside diameter
d
distance between any two points at 180° to each other around the inside of a single section across the tube
NOTE Unless otherwise specified, the limits on the inside diameter shall include all allowances for ovality (lack of
circularity).
See Figure 1.
2 © ISO 2010 – All rights reserved

3.5
wall thickness
t
thickness measured at a right angle across the tube wall
See Figure 1.
3.6
ovality
difference between the larger and smaller measures of the outside diameter where these are taken at right
angles to each other around a single section across the tube
See Figure 2.
3.7
concentricity
lack of coaxiality
axis of the outside diameter being non-coincident with the axis of the inside diameter
NOTE As the position of the axes is difficult to determine in practice, it is defined as half the variation in
...