ISO 7148-2

Plain bearings — Testing of the tribological behaviour of bearing materials — Part 2: Testing of polymer-based bearing materials

This part of ISO 7148 specifies tribological tests of polymer-based plain bearing materials under specified working conditions, i.e. load, sliding velocity and temperature, with and without lubrication. From the test results, data are obtained which indicate the relative tribological behaviour of metal-polymer and polymer-polymer rubbing parts. The purpose of this part of ISO 7148 is to obtain, for polymer material combinations used in plain bearings, reproducible measured values for friction and wear under specified and exactly-defined test conditions without lubrication (dry surfaces) and with lubrication (boundary lubrication). The test results give useful information for practical application only if all parameters of influence are identical. The more the test conditions deviate from the actual application, the greater the uncertainty of the applicability of the results.

Paliers lisses — Essai du comportement tribologique des matériaux antifriction — Partie 2: Essai des matériaux pour paliers à base de polymère

General Information

• Status: Not Published
• ICS: 21.100.10 - Plain bearings
• Technical Committee: ISO/TC 123/SC 2 - Materials and lubricants, their properties, characteristics, test methods and testing conditions
• Current Stage: 6000 - International Standard under publication
• Start Date: 05-Dec-2025
• Completion Date: 13-Dec-2025

Relations

• Revises: ISO 7148-2:2012 - Plain bearings — Testing of the tribological behaviour of bearing materials — Part 2: Testing of polymer-based bearing materials
• Effective Date: 21-Oct-2023

Standards Content (Sample)

FINAL DRAFT
International
Standard
ISO/FDIS 7148-2
ISO/TC 123/SC 2
Plain bearings — Testing of the
Secretariat: DIN
tribological behaviour of bearing
Voting begins on:
materials —
2025-10-09
Part 2:
Voting terminates on:
2025-12-04
Testing of polymer-based bearing
materials
Paliers lisses — Essai du comportement tribologique des
matériaux antifriction —
Partie 2: Essai des matériaux pour paliers à base de polymère
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 SUPPOR TING DOCUMENTATION.
IN ADDITION TO THEIR EVALUATION AS
BEING ACCEPTABLE FOR INDUSTRIAL, TECHNO-
LOGICAL, COMMERCIAL AND USER PURPOSES, DRAFT
INTERNATIONAL STANDARDS MAY ON OCCASION HAVE
TO BE CONSIDERED IN THE LIGHT OF THEIR POTENTIAL
TO BECOME STAN DARDS TO WHICH REFERENCE MAY BE
MADE IN NATIONAL REGULATIONS.
Reference number
ISO/FDIS 7148-2:2025(en) © ISO 2025

FINAL DRAFT
ISO/FDIS 7148-2:2025(en)
International
Standard
ISO/FDIS 7148-2
ISO/TC 123/SC 2
Plain bearings — Testing of the
Secretariat: DIN
tribological behaviour of bearing
Voting begins on:
materials —
Part 2:
Voting terminates on:
Testing of polymer-based bearing
materials
Paliers lisses — Essai du comportement tribologique des
matériaux antifriction —
Partie 2: Essai des matériaux pour paliers à base de polymère
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 SUPPOR TING DOCUMENTATION.
© ISO 2025
IN ADDITION TO THEIR EVALUATION AS
All rights reserved. Unless otherwise specified, or required in the context of its implementation, no part of this publication may
BEING ACCEPTABLE FOR INDUSTRIAL, TECHNO-
LOGICAL, COMMERCIAL AND USER PURPOSES, DRAFT
be reproduced or utilized otherwise in any form or by any means, electronic or mechanical, including photocopying, or posting on
INTERNATIONAL STANDARDS MAY ON OCCASION HAVE
the internet or an intranet, without prior written permission. Permission can be requested from either ISO at the address below
TO BE CONSIDERED IN THE LIGHT OF THEIR POTENTIAL
or ISO’s member body in the country of the requester.
TO BECOME STAN DARDS TO WHICH REFERENCE MAY BE
MADE IN NATIONAL REGULATIONS.
ISO copyright office
CP 401 • Ch. de Blandonnet 8
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Phone: [phone]
Email: [e-mail]
Website: www.iso.org
Published in Switzerland Reference number
ISO/FDIS 7148-2:2025(en) © ISO 2025

ii
ISO/FDIS 7148-2:2025(en)
Contents Page
Foreword .v
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Symbols and units. 1
5 Special features for the tribological testing of polymer-based materials . 3
6 Test methods . 3
6.1 General .3
6.2 Test method A — Pin-on-disc .6
6.3 Test method B — Block-on-ring .7
6.4 Test method C — Rotation under thrust load .8
6.5 Test method D — Sphere-on-prism .8
6.6 Test method E — Plain bearing-on-shaft .9
6.7 Test method F— Linear guidance system .10
7 Test specimens .11
7.1 Data required .11
7.2 Polymer-based plain bearing materials .11
7.3 Materials of mating component .11
7.4 Dimensions of test specimens . 12
7.4.1 General . 12
7.4.2 Disc . 12
7.4.3 Ring . 12
7.4.4 Pin . 12
7.4.5 Block . 12
7.4.6 Sphere. 12
7.4.7 Prism . 13
7.4.8 Plain bearing .14
7.4.9 Shaft . 15
7.4.10 Sleeve . 15
7.4.11 Plate . 15
7.4.12 Slider .16
7.5 Preparation of the test specimens .16
8 Test methods and test equipment . 17
8.1 General .17
8.2 Test method A — Pin-on-disc .17
8.3 Test method B — Block-on-ring .18
8.4 Test method C — Rotation under thrust load .18
8.4.1 General .18
8.4.2 Test method C1.18
8.4.3 Test method C2 .18
8.5 Test method D — Sphere-on-prism .19
8.6 Test method E — Plain bearing-on-shaft .19
8.6.1 General .19
8.6.2 Test method E1 .19
8.6.3 Test method E2 .19
8.6.4 Test method E3 .19
8.7 Test method F— Linear guidance system .19
9 Lubrication .20
9.1 General . 20
9.2 Dry (dr) . 20
9.3 Grease (gr) . 20
9.4 Oil (oi) . 20

iii
ISO/FDIS 7148-2:2025(en)
9.5 Solid lubricant (so) . 20
10 Designation .20
11 Test conditions .21
11.1 Environmental conditions .21
11.2 Mounting of the test specimens .21
11.3 Test variables .21
12 Test procedure .23
12.1 Running-in . 23
12.2 Carrying out the tests . 23
13 Test report .24
13.1 General .24
13.2 Test results .24
Annex A (informative) Test report .25
Bibliography .27

iv
ISO/FDIS 7148-2:2025(en)
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.
The procedures used to develop this document and those intended for its further maintenance are described
in the ISO/IEC Directives, Part 1. In particular, the different approval criteria needed for the different types
of ISO document should be noted. This document was drafted in accordance with the editorial rules of the
ISO/IEC Directives, Part 2 (see www.iso.org/directives).
ISO draws attention to the possibility that the implementation of this document may involve the use of (a)
patent(s). ISO takes no position concerning the evidence, validity or applicability of any claimed patent
rights in respect thereof. As of the date of publication of this document, ISO had not received notice of (a)
patent(s) which may be required to implement this document. However, implementers are cautioned that
this may not represent the latest information, which may be obtained from the patent database available at
www.iso.org/patents. ISO shall not be held responsible for identifying any or all such patent rights.
Any trade name used in this document is information given for the convenience of users and does not
constitute an endorsement.
For an explanation of the voluntary nature of standards, the meaning of ISO specific terms and expressions
related to conformity assessment, as well as information about ISO's adherence to the World Trade
Organization (WTO) principles in the Technical Barriers to Trade (TBT), see www.iso.org/iso/foreword.html.
This document was prepared by Technical Committee ISO/TC 123, Plain bearings, Subcommittee SC 2,
Materials and lubricants, their properties, characteristics, test methods and testing conditions.
This third edition cancels and replaces the second edition (ISO 7148-2:2012), which has been technically
revised.
The main changes are as follows:
— the descriptive statement in Clause 1 about matching test conditions to practical applications have been
moved to Clause 5;
— Clause 2 "Normative references" has been updated;
— Clause 3 "Terms and definitions" has been added and subsequent clauses have been renumbered;
— Table 1 and Table A.1 have been updated with symbols and units;
— Clause 6 has been updated and a new Table 2 has been added to compare test methods;
— Clause 7 has been updated where example of warning messages have been added;
— subclause 7.4.9 and subclause 8.3 have been updated with runout tolerance requirements to make the
test more accurate;
— Clause 11 has been updated where the relative humidity symbol "RH" has been added;
— Clause 13 "Test report" has been changed to make the reports completer; text have been moved to make
the procedures clearer;
— subclause 7.4.6 and subclause 8.2 have been updated to include footnotes and references have been added.
— footnotes have been added to "balls for ball bearings" in subclause 7.4.6 and "precision rolling bearings"
in subclause 8.2, and bibliographies have been added.

v
ISO/FDIS 7148-2:2025(en)
A list of all parts in the ISO 7148 series can be found on the ISO website.
Any feedback or questions on this document should be directed to the user’s national standards body. A
complete listing of these bodies can be found at www.iso.org/members.html.

vi
FINAL DRAFT International Standard ISO/FDIS 7148-2:2025(en)
Plain bearings — Testing of the tribological behaviour of
bearing materials —
Part 2:
Testing of polymer-based bearing materials
1 Scope
This document specifies tribological tests of polymer-based plain bearing materials under specified working
conditions, i.e. load, sliding velocity and temperature, with and without lubrication. From the test results,
data are obtained which indicate the relative tribological behaviour of metal-polymer and polymer-polymer
rubbing parts.
The purpose of this document is to obtain, for polymer material combinations used in plain bearings,
reproducible measured values for friction and wear under specified and exactly-defined test conditions
without lubrication (dry surfaces) and with lubrication (boundary lubrication).
2 Normative references
The following documents are referred to in the text in such a way that some or all of their content constitutes
requirements 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 4378-2, Plain bearings — Terms, definitions, classification and symbols — Part 2: Friction and wear
ISO 4378-3, Plain bearings — Terms, definitions, classification and symbols — Part 3: Lubrication
ISO 4385, Plain bearings — Compression testing of bearing materials
ISO 6691, Thermoplastic polymers for plain bearings — Classification and designation
3 Terms and definitions
For the purposes of this document, the terms and definitions given in ISO 4378-2, ISO 4378-3 the following apply.
ISO and IEC maintain terminological databases for use in standardization at the following addresses:
— ISO Online browsing platform: available at https:// www .iso .org/ obp
— IEC Electropedia: available at https:// www .electropedia .org/
3.1
conditioning
one or more operations intended to bring a sample or test specimen into a state of equilibrium with regard
to temperature and humidity.
[SOURCE: ISO 291:2008, 3.4]
4 Symbols and units
See Table 1.
ISO/FDIS 7148-2:2025(en)
Table 1 — Symbols, units and abbreviated terms
Symbol Term Unit
A, B, C, D, E, F
Test method -
(C1, C2, E1, E2,
E3)
a Sliding distance km
b Machined plate length mm
b Machined plate width mm
dr Dry -
F
f
f -
Coefficient of friction; ratio between friction force and normal force, i.e.: f =
F
n
F Friction force N
f
F Normal force N
n
gr Grease -
t Machined plate thickness mm
Coefficient of wear, volumetric wear rate related to the normal force, i.e.:
V w
K mm /(N·km)
w v
w
K = =
w
Fa× F
n n
l Linear wear as measured by change in distance mm
w
oi Oil -
p Specific force per unit area (force/projected contact area) N/mm
Thermal constant of the test equipment.
Q °C·m·s/N
QT=−()Tf/1××pU× 0
()
lim amb
RH Relative humidity %
Ra Surface parameter, arithmetic mean height µm
Rk Surface parameter, core height µm
Rpk Surface parameter, reduced peak height µm
Rvk Surface parameter, reduced pit depth µm
R Compression strength N/mm
cF
R 0,2 % Compression limit N/mm
cp0,2
so Solid lubricant -
Specimen's temperature near the sliding surface during testing under steady-
T °C
state conditions
T Ambient temperature °C
amb
T Glass transition temperature °C
g
T Maximum permissible temperature °C
lim
t Plate thickness mm
t Test duration h
Ch
U Sliding velocity m/s
V Material removed by wear as measured by change in volume mm
W
l
w
w mm/km
Linear wear rate, i.e.; w =
l
l
a
V
w
w mm /km
Volumetric wear rate, i.e.: w =
v
v
a
η Lubricant dynamic viscosity Pa·s

ISO/FDIS 7148-2:2025(en)
5 Special features for the tribological testing of polymer-based materials
Polymers have a low thermal conductivity and a low melting temperature, so that heat resulting from contact
friction can lead to partial melting and hence thermal wear. Due to the high thermal expansion of polymers
(up to 10 times higher than that of steel), results obtained can be misleading because the test specimens
have expanded under frictional heat. Hence, allowance shall be made for the effects of thermal expansion
(change of clearance) and thermal conductivity (melting) when assessing the results. Where possible the
temperature of both test specimens should be controlled.
Polymers have a glass transition temperature, T , which depends on their chemical structure. At this
g
temperature, their physical properties and their tribological behaviour can change.
Injection-moulded polymer surfaces have different properties from machined surfaces. The test specimens
shall be tested with the same surface conditions as they have in practical application.
Reinforcements and fillers, i.e. fibres, can lead to very strong anisotropy of the material and influence its
wear behaviour depending on fibre orientation. The test specimens should have the same fibre orientation
as in practical application.
In order to avoid stick-slip, the test rig shall be very stiff and shall not be susceptible to vibrations.
The tribological behaviour of polymers depends very strongly on the material combination, which part
moves and which part remains stationary. The test system shall be similar to practical application.
Polymers show wear processes that are different from that of metals. There are not only abrasive wear
processes with powder-like wear debris, but also adhesive wear processes with the creation of transfer
scoring
layers which can be smooth or rough. Also , plastic deformation or even thermal wear is possible.
Therefore, wear cannot be gravimetrically measured in all cases and the wear status shall be judged
after the tests (whether the surfaces are fine- or coarse- grained, scored or plucked out, scaled, melted or
plastically deformed).
Some polymers can show poor repeatability of the results and require repeated testing (i.e. six or more
repetitions).
The preparation and preparatory treatment (e.g. conditioning, storage, cleaning) of the test specimens can
have a high influence on performance.
In some thermoplastics, e.g. polyamides, moisture absorption effects a gradual change in linear dimensions
and modifies their mechanical properties. Environmental parameters should, therefore, be controlled in the
test array. Moisture absorption prohibits gravimetrical measurement of wear.
The test results give useful information for practical application only if all parameters of influence are
identical. The more the test conditions deviate from the actual application, the greater the uncertainty of the
applicability of the results.
6 Test methods
6.1 General
The more the test conditions deviate from the actual application, the greater the uncertainty of the
applicability of the results. Different test methods are provided for tests in accordance with this document
so that the following contact geometries are available. An overview on these test methods is given in Table 2.
The test methods should correspond to the practical application as closely as possible.

ISO/FDIS 7148-2:2025(en)
Table 2 — Overview on test methods
Rotating
Contact Load direc-
Test method moving Sketch Simulation
a
mode tion
b
part
A
PP Thrust Disc
Pin-on-disc
B
CC Radial Ring
Block -on-
ring
C1
PP Thrust Sleeve
Sleeve-to-
Simulation under approx-
sleeve
imated practical testing
conditions and model
systems
C2
PP Thrust Sleeve
Sleeve-to-
plate
a
Key: C——Cylindrical surface; P——Plane; S——Spherical surface;
b
Usually, the base and larger body is determined to be the stationary body, while the smaller one as the counter-body is to be
designated in motion. However, the designation is sometimes derived from the practical application.
c
Not rotating but linear oscillating.

ISO/FDIS 7148-2:2025(en)
TTabablele 2 2 ((ccoonnttiinnueuedd))
Rotating
Contact Load direc-
Test method moving Sketch Simulation
a
mode tion
b
part
D
Thrust and
PS Sphere
Sphere-on-
Radial
prism
E
CC Radial Shaft
Plain bear-
ing-on-shaft
Simulation of real rub-
bing contacts
F
c
PP Thrust Slider
Linear guid-
ance system
a
Key: C——Cylindrical surface; P——Plane; S——Spherical surface;
b
Usually, the base and larger body is determined to be the stationary body, while the smaller one as the counter-body is to be
designated in motion. However, the designation is sometimes derived from the practical application.
c
Not rotating but linear oscillating.

ISO/FDIS 7148-2:2025(en)
6.2 Test method A — Pin-on-disc
Figure 1 shows a schematic drawing of a disc and pin assembly.
a) A1(vertical) b) A2(horizontal)
Key
1 disc
2 pin
NOTE This method has both advantages and disadvantages, which are as follows:
Advantages:
—  basic testing of simple test specimens;
—  testing of tribological properties;
—  no increase of sliding surface area due to wear;
—  initial ranking of materials;
—  with and without lubrication.
Disadvantages:
—  the pin can wipe off lubricant;
—  no injection moulding of the pin and the disc because of problems with shrinkage, unless the specimens are
mechanically machined after injection moulding;
—  fibre orientation has to be taken into account for specimens with fibre reinforced material.
Figure 1 — Test method A — Pin-on-disc

ISO/FDIS 7148-2:2025(en)
6.3 Test method B — Block-on-ring
Figure 2 shows a schematic drawing of a block and ring assembly.
Key
1 ring
2 block
NOTE This method has both advantages and disadvantages, which are as follows:
Advantages:
—  basic testing of simple test specimens;
—  testing of tribological properties;
—  initial ranking of materials;
—  with and without lubrication.
Disadvantages:
—  the block can wipe off lubricant;
—  no injection moulding of the block and the ring because of problems with shrinkage, unless the specimens are
mechanically machined after injection moulding;
—  fibre orientation has to be taken into account for specimens with fibre reinforced material.
Figure 2 — Test method B — Block-on-ring

ISO/FDIS 7148-2:2025(en)
6.4 Test method C — Rotation under thrust load
Figure 3 shows a schematic drawing of a sleeve-to-sleeve and sleeve-to-plate assembly.
a) C1 — Sleeve-to-sleeve b) C2 — Sleeve-to-plate
Key
1 sleeve
2 plate
NOTE This method has both advantages and disadvantages, which are as follows:
Advantages:
—  basic testing of simple specimens;
—  injection-moulded test specimens available;
—  testing of tribological properties;
—  initial ranking of material;
—  no increase of sliding surface area due to wear;
—  continuous sliding between specimens;
—  with and without lubrication.
Disadvantages:
—  plastic deformation affects results;
—  no injection moulding of the specimen because of problems with shrinkage, unless the specimens are mechanically
machined after injection moulding;
—  thermally problematic due to complete overlap;
—  wear particles cannot be removed out of the contacting area.
Figure 3 — Rotation under thrust load
6.5 Test method D — Sphere-on-prism
Figure 4 shows a schematic drawing of a sphere and prism assembly.

ISO/FDIS 7148-2:2025(en)
Key
1 sphere
2 prism
NOTE This method has both advantages and disadvantages, which are as follows:
Advantages:
—  testing of polymer/polymer or polymer/metal combinations;
—  with and without lubrication (test specimen contains reservoir for lubricant);
—  testing of lubricant’s interaction with polymers;
—  injection-moulded test specimens available;
—  self-adjustment of the alignment of the sliding couple;
Disadvantages:
—  plastic deformation can affect results;
—  increasing sliding surface area due to wear under boundary lubrication and dry condition.
Figure 4 — Test method D — Sphere-on-prism
6.6 Test method E — Plain bearing-on-shaft
Figure 5 shows a schematic drawing of a plain bearing and shaft assembly.

ISO/FDIS 7148-2:2025(en)
Key
1 shaft
2 plain bearing
NOTE This method has both advantages and disadvantages, which are as follows:
Advantages:
—  best simulation of all possible systems;
—  testing of original or scaled bearings;
—  prediction of practical behaviour;
—  with and without lubrication.
Disadvantages:
—  long testing time (accelerated testing can cause excessive frictional heating);
—  difficult alignment of the test bearing;
—  increasing sliding surface area due to wear under boundary lubrication and dry condition.
Figure 5 — Test method E — Plain bearing-on-shaft
6.7 Test method F— Linear guidance system
Figure 6 shows a schematic drawing of a slider and plate assembly.
Key
1 slider
2 plate
NOTE This method has both advantages and disadvantages, which are as follows:
Advantages:
—  basic testing of simple test specimens;
—  testing of tribological properties;
—  no increase of sliding surface area due to wear;
—  initial ranking of materials;
—  simulation of linear guidance system ;

ISO/FDIS 7148-2:2025(en)
—  with and without lubrication.
Disadvantages:
—  the slider can wipe off lubricant;
—  no injection moulding of the slider and the plate because of problems with shrinkage, unless the specimens are
mechanically machined after injection moulding;
—  fibre orientation has to be taken into account for specimens with fibre reinforced material.
Figure 6 — Test method F — Linear guidance system
7 Test specimens
7.1 Data required
For one series of tests, several specimens of one material shall be from the same batch, with uniform state
after conditioning and uniform finish of the sliding surface. Machined and injection-moulded specimens can
create different results because crystallinity can vary with depth from the surface. They should be tested
separately.
The structural condition of the mating materials constitutes an essential factor as far as the repeatability of
the test results is concerned, the following information shall be provided:
a) material specification and composition, including fillers or details of fibre reinforcement (as specified in
ISO 6691);
b) method of manufacture;
c) structure, e.g. density, degree of crystallinity;
d) mechanical material properties, e.g. Shore hardness, 0,2 % compression limit, R (as specified in
cp0,2
ISO 4385), compression strength, R ;
cF
e) state of conditioning, e.g. moisture content;
f) surface condition and surface roughness, Ra (under certain conditions, Rpk, Rk, Rvk of the specimens
should also be controlled), e.g. injection-moulded, machined (as specified in ISO 2818), turned, ground,
lapped, polished, milled.
7.2 Polymer-based plain bearing materials
These can be made by moulding, injection moulding or by cutting bar or tube to length or by machining all
over from semi-finished materials or by cutting from injection-moulded or laminated (composite) plates.
If fibre-reinforced polymers are to be tested, the fibres shall lie in the same direction in the test as in the
final product, e.g. parallel or perpendicular to the sliding surface.
7.3 Materials of mating component
All metallic and polymer-based materials can be considered as mating materials. The choice should be the
same as in practical application. In technical applications, all systems are possible, e.g. gear box of aluminium
with injection-moulded gears and shafts of polyoxymethylene (POM). The mating materials shall have the
same sliding couple, e.g. rotating POM disc or ball on fixed pin or prism out of aluminium. In this case, the
reverse combination POM pin on aluminium disc leads to errors in evaluation.

ISO/FDIS 7148-2:2025(en)
7.4 Dimensions of test specimens
7.4.1 General
If dimensions other than those described as follows are used, the results will not be comparable due to the
effects of transfer films and heat dissipation.
7.4.2 Disc
The disc should have the following dimensions:
— outside diameter: 110 mm;
— inside diameter: 60 mm;
— radius of the sliding track: (51,5 ± 0,2) mm;
— width: 10 mm.
The basic form of the disc is identical to shaft thrust washer of a thrust ball bearing.
The said thrust ball bearing shaft washer belongs to dimension series 13 according to ISO 104. The
commercial product designation of bearing manufacturers is 51312.
CAUTION — Only the shaft washer back face can be used for the test. Alternatively, a shaft washer
of a cylindrical roller thrust bearing dimension series 93 according to ISO 104 can be used. The
commercial product designation of bearing manufacturers is 89312.
CAUTION — The shaft washer back face and the raceway of the shaft washer have different surface
conditions.
7.4.3 Ring
The ring should have an outside diameter of 40 mm and a width corresponding at least to the width of the block.
7.4.4 Pin
The pin should have a diameter of 3 mm for injection-moulded materials. For fibre-reinforced materials, a
larger diameter is preferred.
If a pin with a diameter greater than 7 mm is used, the radius of the sliding track has to be reduced or the
disc diameter increased. Means shall be provided for preventing rotation of the pin.
The free length of the pin should not exceed 2 mm. Due to its dimensions, it is possible to make the 3 mm
diameter polymer pin out of a standard tension bar in accordance with ISO 527-3 or ISO 527-2. This allows
the correlation of wear and strength tests.
7.4.5 Block
The preferred basic dimensions of the block should be 10 mm × 10 mm × 20 mm. If a suitably large component
is not available, the block may, as an exception, be used with a length of 10 mm. The roughness of the block
depends on the machining conditions, e.g. milling or turning. The radius of the rubbing surface of the block
should be a minimum of 1,001 times the radius of the ring. If the maximum radius exceeds 1,003 times the
radius of the ring (line contact), the running-in period can be unduly prolonged (see 12.1).
7.4.6 Sphere
The sphere should have a diameter of 12,7 mm. Thermoplastics can be injection-moulded (see Figure 7).
1)
Spheres made out of metals are commercially available (balls for ball bearings or valves).
1) See also ISO 3290-1.
ISO/FDIS 7148-2:2025(en)
Dimensions in millimetres
Key
1 six-flat mount with cylindrical hole
2 position of injection molding port
Figure 7 — Example of an injection-moulded sphere
7.4.7 Prism
The prism has a preferred special shape. If injection-moulded, the prism specimen shall have a uniform wall
thickness (2 mm) and metallic support (see Figure 8) in order to avoid deformation. Alternatively, machined
plates can be fitted into a special mount (see Figure 9).
Dimensions in millimetres
Key
1 metallic support
2 position of injection molding port
Figure 8 — Example of an injection-moulded prism

ISO/FDIS 7148-2:2025(en)
Key
1 metal holder
2 machined plate
Figure 9 — Example of machined plates, inserted in a metallic holder
7.4.8 Plain bearing
The plain bearing bush can be made by machining or by injection moulding. Depending on the test equipment
used, it is possible to use plain bearings with different inside diameters, the preferred inside diameters
being 20 mm, 5 mm or 1 mm, the latter being used for special applications, the width/diameter ratio being
0,75 or 1.
The diameter, bearing clearance, wall thickness and type of bearing used (bush or half bearing) shall be
indicated in the test report. Smaller plain bearings should have a flange in order to allow to fix them in the
mount (see Figure 10). The sliding surface area shall lie within the cylindrical part of the plain bearing.
Key
1 flange
2 sliding surface
Figure 10 — Example of an injection-moulded plain bearing with step and chamfer in the bore

ISO/FDIS 7148-2:2025(en)
7.4.9 Shaft
The shaft piece used for the test shall be made with a circular run-out tolerance 5 μm maximum and a
circularity of not more than 5 μm. Irrespective of the test equipment used, it shall be ensured that the test
specimens (test bush and shaft) mounted in the test equipment have a maximum angular deviation of 0,05°
prior to the test and in the absence of a normal force. The diameter of the shaft (i.e. the bearing clearance)
shall be sufficient to allow for thermal expansion of the bush (risk of bore closure leading to seizure) and
depends on the wall thickness, temperature of operation and material properties. The (cold) diametral
clearance can vary from 0,003 times to 0,01 times the shaft diameter, being kept as small as possible
consistent with avoiding seizure.
7.4.10 Sleeve
The sleeve can be made by machining or injection moulding. The preferred basic dimensions of the sleeve
are shown in Figure 11.
Dimensions in millimetres
Figure 11 — Dimensions of sleeve
7.4.11 Plate
The plate can be made by machining or injection moulding. The preferred basic dimensions of the plate are
shown in Figure 12.
ISO/FDIS 7148-2:2025(en)
Dimensions in millimetres
Key
t 2 to 5
Figure 12 — Dimensions of plate
7.4.12 Slider
The slider can be made by machining or injection moulding. The slider shall be ensured that the friction
surface is free of scratch, pitting, shrinkage mark, and other visible defects that will affect the test result.
The flatness of the slider shall be within 5 μm.
7.5 Preparation of the test specimens
7.5.1 The preparation applies to bearing materials and mating materials.
Immediately prior to the test, a cleaning procedure shall be carried out in order to avoid influences on the
sliding behaviour which can result from remainders of the cutting solutions and other substances that can
possibly have been used in the manufacture of the test specimens.
7.5.2 The following cleaning procedures shall be carried out.
a) Step1: Brush loose particles with a soft brush from the test specimens. Then immerse the test specimens
−4
in three separate baths of a high-quality solvent (with a maximum impurity volume of 5 × 10 %)
which is suitable for the type of material to be tested. Suitable solvents are, for example, 2-propanol,
ethanol, acetone, fluorocarbons, some water solutions or cyclohexane. In all cases, the compatibility of
plastic material and solvent shall be ensured. Data pertaining to the cleaning procedure and the solvent
selected shall be included in the test report.
Warning:
2-propanol, ethanol, acetone, and cyclohexane are flammable.
2-propanol act as central nervous system depressants.

ISO 7010-W001 ISO 7010-W021
Cyclohexane and fluorocarbons are harmful to health and dangerous to the environment.

ISO/FDIS 7148-2:2025(en)
ISO 7010-W071 ISO 7010-W072
b) Step2: The test specimens shall be dried in an oven at a maximum temperature of 60 °C.
c) Step3: Test specimens of polymers which are affected by humidity, e.g. polyamides, shall be pre-
conditioned prior to the test at standard atmosphere (23 °C and 50 % air humidity) f
...

Date:2025-07-08
ISO/FDIS 7148-2:2025(en)
ISO /TC 123/SC 2/WG
Secretariat: DIN
Date:
Plain bearings — Testing of the tribological behaviour of bearing
materials —
Part 2:
Testing of polymer-based bearing materials
Paliers lisses — Essai du comportement tribologique des matériaux antifriction —
Partie 2: Essai des matériaux pour paliers à base de polymère
FDIS stage
ISO/FDIS 7148-2:2025(en)
All rights reserved. Unless otherwise specified, or required in the context of its implementation, no part of this publication
may be reproduced or utilized otherwise in any form or by any means, electronic or mechanical, including photocopying,
or posting on the internet or an intranet, without prior written permission. Permission can be requested from either ISO
at the address below or ISO'sISO’s member body in the country of the requester.
ISO Copyright Office copyright office
CP 401 • Ch. de Blandonnet 8
CH-1214 Vernier, Geneva
Phone: + 41 22 749 01 11
Email: [e-mail]
E-mail: [e-mail]
Website: www.iso.orgwww.iso.org
Published in Switzerland.
ii
ISO/FDIS 7148-2:2025(en)
Contents Page
Foreword . v
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Symbols and units . 2
5 Special features for the tribological testing of polymer-based materials . 3
6 Test methods . 4
7 Test specimens . 17
8 Test methods and test equipment . 27
9 Lubrication . 31
10 Designation . 31
11 Test conditions . 32
12 Test procedure . 34
13 Test report . 35
Annex A (informative) Test report . 37
Bibliography . 39

Foreword . v
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Symbols and units . 1
5 Special features for the tribological testing of polymer-based materials . 3
6 Test methods . 4
6.1 General . 4
6.2 Test method A — Pin-on-disc . 5
6.3 Test method B — Block-on-ring . 6
6.4 Test method C — Rotation under thrust load . 7
6.5 Test method D — Sphere-on-prism . 8
6.6 Test method E — Plain bearing-on-shaft . 9
6.7 Test method F— Linear guidance system . 9
7 Test specimens . 10
7.1 Data required . 10
7.2 Polymer-based plain bearing materials . 10
7.3 Materials of mating component . 11
7.4 Dimensions of test specimens . 11
7.4.1 General . 11
7.4.2 Disc . 11
7.4.3 Ring . 11
7.4.4 Pin . 11
7.4.5 Block . 11
© ISO 2025 – All rights reserved
iii
ISO/FDIS 7148-2:2025(en)
7.4.6 Sphere . 12
7.4.8 Plain bearing . 14
7.4.9 Shaft . 14
7.4.10 Sleeve . 14
7.4.11 Plate . 15
7.4.12 Slider . 16
7.5 Preparation of the test specimens . 16
8 Test methods and test equipment . 17
8.1 General . 17
8.2 Test method A — Pin-on-disc . 17
8.3 Test method B — Block-on-ring . 17
8.4 Test method C — Rotation under thrust load . 18
8.4.1 General . 18
8.4.2 Test method C1. 18
8.4.3 Test method C2. 18
8.5 Test method D — Sphere-on-prism . 18
8.6 Test method E — Plain bearing-on-shaft . 19
8.6.1 General . 19
8.6.2 Test method E1 . 19
8.6.3 Test method E2 . 19
8.6.4 Test method E3 . 19
8.7 Test method F— Linear guidance system . 19
9 Lubrication . 20
9.1 General . 20
9.2 Dry (dr) . 20
9.3 Grease (gr) . 20
9.4 Oil (oi) . 20
9.5 Solid lubricant (so). 20
10 Designation . 20
11 Test conditions . 21
11.1 Environmental conditions . 21
11.2 Mounting of the test specimens . 21
11.3 Test variables . 21
12 Test procedure . 23
12.1 Running-in . 23
12.2 Carrying out the tests . 24
13 Test report . 24
13.1 General . 24
13.2 Test results . 24
Annex A (informative) Test report . 25
Bibliography . 27

iv
ISO/FDIS 7148-2:2025(en)
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.
The procedures used to develop this document and those intended for its further maintenance are described
in the ISO/IEC Directives, Part 1. In particular, the different approval criteria needed for the different types of
ISO document should be noted. This document was drafted in accordance with the editorial rules of the
ISO/IEC Directives, Part 2 (see www.iso.org/directives).
ISO draws attention to the possibility that the implementation of this document may involve the use of (a)
patent(s). ISO takes no position concerning the evidence, validity or applicability of any claimed patent rights
in respect thereof. As of the date of publication of this document, ISO had not received notice of (a) patent(s)
which may be required to implement this document. However, implementers are cautioned that this may not
represent the latest information, which may be obtained from the patent database available at
www.iso.org/patents.www.iso.org/patents. ISO shall not be held responsible for identifying any or all such
patent rights.
Any trade name used in this document is information given for the convenience of users and does not
constitute an endorsement.
For an explanation of the voluntary nature of standards, the meaning of ISO specific terms and expressions
related to conformity assessment, as well as information about ISO's adherence to the World Trade
Organization (WTO) principles in the Technical Barriers to Trade (TBT), see
www.iso.org/iso/foreword.htmlwww.iso.org/iso/foreword.html.
This document was prepared by Technical Committee ISO/TC 123, Plain bearings, Subcommittee SC 2,
Materials and lubricants, their properties, characteristics, test methods and testing conditions.
This third edition cancels and replaces the second edition (ISO 7148-2:2012), which has been technically
revised.
The main changes are as follows:
— — Move the descriptive statement in Clause 11 about matching test conditions to practical applications
to Clause 5;have been moved to 5;
— — Clause 22 "Normative references" has been updated;
— — Clause 33 "Terms and definitions" has been added and subsequent clauses have been renumbered;
— — Table 1Table 1 and Table A.1Table A.1 have been updated with symbols and units;
— — Clause 66 has been updated and a new Table 2Table 2 has been added to compare test methods;
— — Clause 77 has been updated where example of warning messages have been added;
— — Clause 7.4.97.4.9 and Clause 8.38.3 have been updated with runout tolerance requirements to make
the test more accurate;
— — Clause 1111 has been updated where the relative humidity symbol "RH" has been added;
© ISO 2025 – All rights reserved
v
ISO/FDIS 7148-2:2025(en)
— — Clause 1313 "Test report" has been changed to make the reports completer; text have been moved to
make the procedures clearer;
— — Clause 7.4.67.4.6 and Clause 8.28.2 have been updated to include footnotes and references have been
added.;
— — Footnotesfootnotes have been added to "balls for ball bearings" in clause 7.4.67.4.6 and "precision
rolling bearings" in clause 8.2,8.2, and bibliographies have been added.
A list of all parts in the ISO 7148 series can be found on the ISO website.
Any feedback or questions on this document should be directed to the user’s national standards body. A
complete listing of these bodies can be found at www.iso.org/members.html.

vi
DRAFT international standard ISO/FDIS 7148-2:2025(en)

Plain bearings — Testing of the tribological behaviour of bearing
materials —
Part 2:
Testing of polymer-based bearing materials
1 Scope
This document specifies tribological tests of polymer-based plain bearing materials under specified working
conditions, i.e. load, sliding velocity and temperature, with and without lubrication. From the test results, data
are obtained which indicate the relative tribological behaviour of metal-polymer and polymer-polymer
rubbing parts.
The purpose of this document is to obtain, for polymer material combinations used in plain bearings,
reproducible measured values for friction and wear under specified and exactly-defined test conditions
without lubrication (dry surfaces) and with lubrication (boundary lubrication).
2 Normative references
The following documents are referred to in the text in such a way that some or all of their content constitutes
requirements 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 527-2, Plastics — Determination of tensile properties — Part 2: Test conditions for moulding and extrusion
plastics
ISO 527-3, Plastics — Determination of tensile properties — Part 3: Test conditions for films and sheets
ISO 4378--2, Plain bearings — Terms, definitions, classification and symbols — Part 2: Friction and wear
ISO 4378--3, Plain bearings — Terms, definitions, classification and symbols — Part 3: Lubrication
ISO 4385, Plain bearings — Compression testing of metallic bearing materials
ISO 6691, Thermoplastic polymers for plain bearings — Classification and designation
3 Terms and definitions
For the purposes of this document, the terms and definitions given in ISO 4378-2 and, ISO 4378-3 the following
apply.
ISO and IEC maintain terminological databases for use in standardization at the following addresses:
— — ISO Online browsing platform: available at https://www.iso.org/obphttps://www.iso.org/obp
— — IEC Electropedia: available at https://www.electropedia.org/https://www.electropedia.org/
ISO/FDIS 7148-2:2025(en)
3.1
conditioning
one or more operations intended to bring a sample or test specimen into a state of equilibrium with regard to
temperature and humidity.
[SOURCE: ISO 291:2008, 3.4]
4 Symbols and units
See Table 1.
See Table 1.
Table 1 — Symbols, units and abbreviated terms
Symbol Term Unit
A, B, C, D, E, F
Test method -
(C1, C2, E1,
E2, E3)
a Sliding distance km
b1 Machined plate length mm
b Machined plate width mm
dr Dry -
F
f
Coefficient of friction; ratio between friction force and normal force, i.e.:
f 
F
f n -
𝐹
𝑓
𝑓=
𝐹
n
Ff Friction force N
Fn Normal force N
gr Grease -
t Machined plate thickness mm
Coefficient of wear, volumetric wear rate related to the normal force, i.e.:
V w
Kw mm /(N·km)
𝑉 𝑤
w v w v
K 𝐾 = =
w
w
𝐹 ×𝑎 𝐹
n n
F a F
nn
l Linear wear as measured by change in distance mm
w
oi Oil -
p𝑝¯
Specific force per unit area (force/projected contact area) N/mm
Thermal constant of the test equipment.
Q ℃°C·m·s/N
QT T  / f pU10 𝑄=(𝑇 −𝑇 )/(𝑓×𝑝¯×𝑈×10 )
  lim 𝑎𝑚𝑏
lim amb
RH Relative humidity %
Ra Surface parameter, arithmetic mean height µm
Rk Surface parameter, core height µm
Rpk Surface parameter, reduced peak height µm
Rvk Surface parameter, reduced pit depth µm
ISO/FDIS 7148-2:2025(en)
Symbol Term Unit
R Compression strength N/mm
cF
Rcp0,2 0,2 % Compression limit N/mm
so Solid lubricant -
Specimen's temperature near the sliding surface during testing under steady-
T °C
state conditions
T Ambient temperature °C
amb
T Glass transition temperature °C
g
T Maximum permissible temperature °C
lim
t Plate thickness mm
tCh Test duration h
U Sliding velocity m/s
V Material removed by wear as measured by change in volume mm
W
l 𝑙
w
w
Linear wear rate, i.e.; 𝑤 =
w 
wl 𝑙 mm/km
l
𝑎
a
𝑉
V w
w
Volumetric wear rate, i.e.: 𝑤 = 3
w w  v mm /km
v
v
𝑎
a
η Lubricant dynamic viscosity Pa·s
5 Special features for the tribological testing of polymer-based materials
Polymers have a low thermal conductivity and a low melting temperature, so that heat resulting from contact
friction can lead to partial melting and hence thermal wear. Due to the high thermal expansion of polymers
(up to 10 times higher than that of steel), results obtained can be misleading because the test specimens have
expanded under frictional heat. Hence, allowance shall be made for the effects of thermal expansion (change
of clearance) and thermal conductivity (melting) when assessing the results. Where possible the temperature
of both test specimens should be controlled.
Polymers have a glass transition temperature, T , which depends on their chemical structure. At this
g
temperature, their physical properties and their tribological behaviour can change.
Injection-moulded polymer surfaces have different properties from machined surfaces. The test specimens
shall be tested with the same surface conditions as they have in practical application.
Reinforcements and fillers, i.e. fibres, can lead to very strong anisotropy of the material and influence its wear
behaviour depending on fibre orientation. The test specimens should have the same fibre orientation as in
practical application.
In order to avoid stick-slip, the test rig shall be very stiff and shall not be susceptible to vibrations.
The tribological behaviour of polymers depends very strongly on the material combination, which part moves
and which part remains stationary. The test system shall be similar to practical application.
Polymers show wear processes that are different from that of metals. There are not only abrasive wear
processes with powder-like wear debris, but also adhesive wear processes with the creation of transfer layers
scoring
which can be smooth or rough. Also , plastic deformation or even thermal wear is possible. Therefore,
wear cannot be gravimetrically measured in all cases and the wear status shall be judged after the tests
© ISO 2025 – All rights reserved
ISO/FDIS 7148-2:2025(en)
(whether the surfaces are fine- or coarse- grained, scored or plucked out, scaled, melted or plastically
deformed).
Some polymers can show poor repeatability of the results and require repeated testing (i.e. six or more
repetitions).
The preparation and preparatory treatment (e.g. conditioning, storage, cleaning) of the test specimens can
have a high influence on performance.
In some thermoplastics, e.g. polyamides, moisture absorption effects a gradual change in linear dimensions
and modifies their mechanical properties. Environmental parameters should, therefore, be controlled in the
test array. Moisture absorption prohibits gravimetrical measurement of wear.
The test results give useful information for practical application only if all parameters of influence are
identical. The more the test conditions deviate from the actual application, the greater the uncertainty of the
applicability of the results.
6 Test methods
6.1 General
The more the test conditions deviate from the actual application, the greater is the uncertainty of the
applicability of the results. Different test methods are provided for tests in accordance with this document so
that the following contact geometries are available. An overview on these test methods is given in
Table 2.Table 2. The test methods should correspond to the practical application as closely as possible.
Table 2 — Overview on test methods
Rotating
Test Contact Load
moving Sketch Simulation
a
method mode direction
b
part
Simulation under
A
approximated practical
PP Thrust Disc
testing conditions and
Pin-on-disc
model systems
ISO/FDIS 7148-2:2025(en)
Rotating
Test Contact Load
moving Sketch Simulation
a
method mode direction
b
part
Simulation under
B
approximated practical
CC Radial Ring
Block -on-
testing conditions and
ring
model systems
C1
PP Thrust Sleeve
Sleeve-to-
sleeve
© ISO 2025 – All rights reserved
ISO/FDIS 7148-2:2025(en)
Rotating
Test Contact Load
moving Sketch Simulation
a
method mode direction
b
part
C2
PP Thrust Sleeve
Sleeve-to-
plate
D
Thrust and
PS Sphere
Sphere-on-
Radial
prism
ISO/FDIS 7148-2:2025(en)
Rotating
Test Contact Load
moving Sketch Simulation
a
method mode direction
b
part
E
Plain
CC Radial Shaft
bearing-on-
shaft
Simulation of real
rubbing contacts
F
Linear
c
PP Thrust Slider
guidance
system
a Key: C——Cylindrical surface; P——Plane; S——Spherical surface;
b Usually, the base and larger body is determined to be the stationary body, while the smaller one as the counter-body is to be
designated in motion. However, the designation is sometimes derived from the practical application.
c Not rotating but linear oscillating.
6.21.1 Test method A — Pin-on-disc
Figure 1
© ISO 2025 – All rights reserved
ISO/FDIS 7148-2:2025(en)
6.2 Test method A — Pin-on-disc
Figure 1 shows a schematic drawing of a disc and pin assembly.

a) A1(vertical)                       b) A2(horizontal)

a) A1(vertical) b) A2(horizontal)
Key
1 disc
2 pin
NOTE This method has both advantages and disadvantages, which are as follows:
Advantages:
—  basic testing of simple test specimens;
—  testing of tribological properties;
—  no increase of sliding surface area due to wear;
—  initial ranking of materials;
—  with and without lubrication.
Disadvantages:
ISO/FDIS 7148-2:2025(en)
—  the pin can wipe off lubricant;
— no injection moulding of the pin and the disc because of problems with shrinkage, unless the specimens are
mechanically machined after injection moulding;
—  fibre orientation has to be taken into account for specimens with fibre reinforced material.
NOTE This method has both advantages and disadvantages, which are as follows:
Advantages:
—  basic testing of simple test specimens;
—  testing of tribological properties;
—  no increase of sliding surface area due to wear;
—  initial ranking of materials;
—  with and without lubrication.
Disadvantages:
—  the pin can wipe off lubricant;
—  no injection moulding of the pin and the disc because of problems with shrinkage, unless the specimens are mechanically
machined after injection moulding;
—  fibre orientation has to be taken into account for specimens with fibre reinforced material.
Figure 1 — Test method A — Pin-on-disc

© ISO 2025 – All rights reserved
ISO/FDIS 7148-2:2025(en)
6.3 Test method B — Block-on-ring
Figure 2Figure 2 shows a schematic drawing of a block and ring assembly.

Key
1 ring
2 block
NOTE This method has both advantages and disadvantages, which are as follows:
Advantages:
—  basic testing of simple test specimens;
—  testing of tribological properties;
—  initial ranking of materials;
—  with and without lubrication.
Disadvantages:
—  the block can wipe off lubricant;
—  no injection moulding of the block and the ring because of problems with shrinkage, unless the specimens are
mechanically machined after injection moulding;
—  fibre orientation has to be taken into account for specimens with fibre reinforced material.
NOTE This method has both advantages and disadvantages, which are as follows:
Advantages:
—  basic testing of simple test specimens;
—  testing of tribological properties;
—  initial ranking of materials;
—  with and without lubrication.
ISO/FDIS 7148-2:2025(en)
Disadvantages:
—  the block can wipe off lubricant;
—  no injection moulding of the block and the ring because of problems with shrinkage, unless the specimens are mechanically
machined after injection moulding;
—  fibre orientation has to be taken into account for specimens with fibre reinforced material.
Figure 2 — Test method B — Block-on-ring
6.41.1 Test method C — Rotation under thrust load
Figure 3
© ISO 2025 – All rights reserved
ISO/FDIS 7148-2:2025(en)
6.4 Test method C — Rotation under thrust load
Figure 3 shows a schematic drawing of a sleeve-to-sleeve and sleeve-to-plate assembly.

a) C1 — Sleeve-to-sleeve b) C2 — Sleeve-to-plate

a) C1 — Sleeve-to-sleeve b) C2 — Sleeve-to-plate
Key
1 sleeve
2 plate
NOTE This method has both advantages and disadvantages, which are as follows:
Advantages:
—  basic testing of simple specimens;
—  injection-moulded test specimens available;
—  testing of tribological properties;
—  initial ranking of material;
—  no increase of sliding surface area due to wear;
—  continuous sliding between specimens;
—  with and without lubrication.
ISO/FDIS 7148-2:2025(en)
Disadvantages:
—  plastic deformation affects results;
— no injection moulding of the specimen because of problems with shrinkage, unless the specimens are mechanically
machined after injection moulding;
—  thermally problematic due to complete overlap;
—  wear particles cannot be removed out of the contacting area.
NOTE This method has both advantages and disadvantages, which are as follows:
Advantages:
—  basic testing of simple specimens;
—  injection-moulded test specimens available;
—  testing of tribological properties;
—  initial ranking of material;
—  no increase of sliding surface area due to wear;
—  continuous sliding between specimens;
—  with and without lubrication.
Disadvantages:
—  plastic deformation affects results;
—  no injection moulding of the specimen because of problems with shrinkage, unless the specimens are mechanically machined
after injection moulding;
—  thermally problematic due to complete overlap;
—  wear particles cannot be removed out of the contacting area.
Figure 3 — Rotation under thrust load
6.5 Test method D — Sphere-on-prism
Figure 4Figure 4 shows a schematic drawing of a sphere and prism assembly.

Key
© ISO 2025 – All rights reserved
ISO/FDIS 7148-2:2025(en)
1 sphere
2 prism
NOTE This method has both advantages and disadvantages, which are as follows:
Advantages:
—  testing of polymer/polymer or polymer/metal combinations;
—  with and without lubrication (test specimen contains reservoir for lubricant);
—  testing of lubricant’s interaction with polymers;
—  injection-moulded test specimens available;
—  self-adjustment of the alignment of the sliding couple;
Disadvantages:
—  plastic deformation can affect results;
—  increasing sliding surface area due to wear under boundary lubrication and dry condition.
NOTE This method has both advantages and disadvantages, which are as follows:
Advantages:
—  testing of polymer/polymer or polymer/metal combinations;
—  with and without lubrication (test specimen contains reservoir for lubricant);
—  testing of lubricant’s interaction with polymers;
—  injection-moulded test specimens available;
—  self-adjustment of the alignment of the sliding couple;
Disadvantages:
—  plastic deformation can affect results;
—  increasing sliding surface area due to wear under boundary lubrication and dry condition.
Figure 4 — Test method D — Sphere-on-prism
6.6 Test method E — Plain bearing-on-shaft
Figure 5Figure 5 shows a schematic drawing of a plain bearing and shaft assembly.

ISO/FDIS 7148-2:2025(en)
Key
1 shaft
2 plain bearing
NOTE This method has both advantages and disadvantages, which are as follows:
Advantages:
—  best simulation of all possible systems;
—  testing of original or scaled bearings;
—  prediction of practical behaviour;
—  with and without lubrication.
Disadvantages:
—  long testing time (accelerated testing can cause excessive frictional heating);
—  difficult alignment of the test bearing;
—  increasing sliding surface area due to wear under boundary lubrication and dry condition.
NOTE This method has both advantages and disadvantages, which are as follows:
Advantages:
—  best simulation of all possible systems;
—  testing of original or scaled bearings;
—  prediction of practical behaviour;
—  with and without lubrication.
Disadvantages:
—  long testing time (accelerated testing can cause excessive frictional heating);
—  difficult alignment of the test bearing;
—  increasing sliding surface area due to wear under boundary lubrication and dry condition.
Figure 5 — Test method E — Plain bearing-on-shaft
6.7 Test method F— Linear guidance system
Figure 6Figure 6 shows a schematic drawing of a slider and plate assembly.
© ISO 2025 – All rights reserved
ISO/FDIS 7148-2:2025(en)
Key
1 slider
2 plate
NOTE This method has both advantages and disadvantages, which are as follows:
Advantages:
—  basic testing of simple test specimens;
—  testing of tribological properties;
—  no increase of sliding surface area due to wear;
—  initial ranking of materials;
—  simulation of linear guidance system ;
—  with and without lubrication.
Disadvantages:
—  the slider can wipe off lubricant;
— no injection moulding of the slider and the plate because of problems with shrinkage, unless the specimens are
mechanically machined after injection moulding;
—  fibre orientation has to be taken into account for specimens with fibre reinforced material.
NOTE This method has both advantages and disadvantages, which are as follows:
Advantages:
—  basic testing of simple test specimens;
—  testing of tribological properties;
—  no increase of sliding surface area due to wear;
—  initial ranking of materials;
—  simulation of linear guidance system ;
—  with and without lubrication.
ISO/FDIS 7148-2:2025(en)
Disadvantages:
—  the slider can wipe off lubricant;
—  no injection moulding of the slider and the plate because of problems with shrinkage, unless the specimens are mechanically
machined after injection moulding;
—  fibre orientation has to be taken into account for specimens with fibre reinforced material.
Figure 6 — Test method F — Linear guidance system
7 Test specimens
7.1 Data required
For one series of tests, several specimens of one material shall be from the same batch, with uniform state
after conditioning and uniform finish of the sliding surface. Machined and injection-moulded specimens can
create different results because crystallinity can vary with depth from the surface. They should be tested
separately.
The structural condition of the mating materials constitutes an essential factor as far as the repeatability of
the test results is concerned, the following information shall be provided:
a) a) material specification and composition, including fillers or details of fibre reinforcement (as
specified in ISO 6691);
b) b) method of manufacture;
c) c) structure, e.g. density, degree of crystallinity;
d) d) mechanical material properties, e.g. Shore hardness, 0,2 % compression limit, R (as
cp0,2
specified in ISO 4385), compression strength, R ;
cF
e) e) state of conditioning, e.g. moisture content;
f) f) surface condition and surface roughness, Ra (under certain conditions, Rpk, Rk, Rvk of the
specimens should also be controlled), e.g. injection-moulded, machined (as specified in ISO 2818), turned,
ground, lapped, polished, milled.
7.2 Polymer-based plain bearing materials
These can be made by moulding, injection moulding or by cutting bar or tube to length or by machining all
over from semi-finished materials or by cutting from injection-moulded or laminated (composite) plates.
If fibre-reinforced polymers are to be tested, the fibres shall lie in the same direction in the test as in the final
product, e.g. parallel or perpendicular to the sliding surface.
7.3 Materials of mating component
All metallic and polymer-based materials can be considered as mating materials. The choice should be the
same as in practical application. In technical applications, all systems are possible, e.g. gear box of aluminium
with injection-moulded gears and shafts of polyoxymethylene (POM). The mating materials shall have the
same sliding couple, e.g. rotating POM disc or ball on fixed pin or prism out of aluminium. In this case, the
reverse combination POM pin on aluminium disc leads to errors in evaluation.
© ISO 2025 – All rights reserved
ISO/FDIS 7148-2:2025(en)
7.4 Dimensions of test specimens
7.4.1 General
If dimensions other than those described as follows are used, the results will not be comparable due to the
effects of transfer films and heat dissipation.
7.4.2 Disc
The disc should have the following dimensions:
— — outside diameter: 110 mm;
— — inside diameter: 60 mm;
— — radius of the sliding track: (51,5 ± 0,2) mm;
— — width: 10 mm.
The basic form of the disc is identical to shaft thrust washer of a thrust ball bearing .
The said thrust ball bearing shaft washer belongs to dimension series 13 according to ISO 104. The commercial
product designation of bearing manufacturers is 51312.
CAUTION — Only the shaft washer back face can be used for the test. Alternatively, a shaft washer of a
cylindrical roller thrust bearing dimension series 93 according to ISO 104 can be used. The
commercial product designation of bearing manufacturers is 89312.
CAUTION — The shaft washer back face and the raceway of the shaft washer have different surface
conditions.
7.4.3 Ring
The ring should have an outside diameter of 40 mm and a width corresponding at least to the width of the
block.
7.4.4 Pin
The pin should have a diameter of 3 mm for injection-moulded materials. For fibre-reinforced materials, a
larger diameter is preferred.
If a pin with a diameter greater than 7 mm is used, the radius of the sliding track has to be reduced or the disc
diameter increased. Means shall be provided for preventing rotation of the pin.
The free length of the pin should not exceed 2 mm. Due to its dimensions, it is possible to make the 3 mm
diameter polymer pin out of a standard tension bar in accordance with ISO 527-3 or ISO 527-2. This allows
the correlation of wear and strength tests.

The said thrust ball bearing shaft washer belongs to dimension series 13 according to ISO 104. The commercial product designation
of bearing manufacturers is 51312.
CAUTION: Only the shaft washer back face can be used for the test. Alternatively a shaft washer of a cylindrical roller thrust bearing
dimension series 93 according to ISO 104 could be used. The commercial product designation of bearing manufacturers is 89312.
CAUTION: The shaft washer back face and the raceway of the shaft washer have different surface conditions.
ISO/FDIS 7148-2:2025(en)
7.4.5 Block
The preferred basic dimensions of the block should be 10 mm × 10 mm × 20 mm. If a suitably large component
is not available, the block may, as an exception, be used with a length of 10 mm. The roughness of the block
depends on the machining conditions, e.g. milling or turning. The radius of the rubbing surface of the block
should be a minimum of 1,001 times the radius of the ring. If the maximum radius exceeds 1,003 times the
radius of the ring (line contact), the running-in period can be unduly prolonged (see 12.1).12.1).
7.4.6 Sphere
The sphere should have a diameter of 12,7 mm. Thermoplastics can be injection-moulded (see
21)
Figure 7).Figure 7). Spheres made out of metals are commercially available (balls for ball bearings or
valves).
See also ISO 3290-1, Rolling bearings – Balls – Part 1: Steel balls.
1)
See also ISO 3290-1.
© ISO 2025 – All rights reserved
ISO/FDIS 7148-2:2025(en)
Dimensions in millimetres
Key
1 six-flat mount with cylindrical hole
2 position of injection molding port
1 six-flat mount with cylindrical hole
2 position of injection molding port
Figure 7 — Example of an injection-moulded sphere
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