ISO 14635-1

Gears — FZG test procedures — Part 1: FZG test method A/8,3/90 for relative scuffing load-carrying capacity of oils

This part of ISO 14635 specifies a test method based on an FZG2_ four-square test machine to determine the relative load-carrying capacity of lubricating oils defined by the gear-surface damage known as scuffing. High surface temperatures due to high surface pressures and sliding velocities can initiate the breakdown of the lubricant films. This test method can be used to assess such lubricant breakdown under defined conditions of temperature, high sliding velocity and stepwise increased load. NOTE This method is technically equivalent to ASTM D 5182-97, DIN 51354-1 and DIN 51354-2, IP 334/90 and CEC L-07-A-95.

Engrenages — Méthodes d'essai FZG — Partie 1: Méthode FZG A/8,3/90 pour évaluer la capacité de charge au grippage des huiles

La présente partie de l'ISO 14635 spécifie une méthode d'essai fondée sur une machine d'essai FZG 2_ ayant pour but de déterminer la capacité de charge d'huiles lubrifiantes, de manière comparative, en ce qui concerne la résistance au grippage. Les températures superficielles élevées, dues à des pressions de contact et des vitesses de glissement élevées, peuvent entraîner la rupture du film lubrifiant. La présente méthode d'essai peut être utilisée pour évaluer des ruptures de lubrifiant sous des conditions définies de température, de vitesses de glissement élevées et de charge augmentant par palier. NOTE La présente méthode est techniquement équivalente aux normes ASTM D 5182 97, DIN 51354-1 et DIN 51354-2, IP 334/90 et CEC L-07-A-95.

General Information

• Status: Not Published
• ICS: 21.200 - Gears
• Technical Committee: ISO/TC 60/SC 2 - Gear capacity calculation
• Drafting Committee: ISO/TC 60/SC 2 - Gear capacity calculation

Relations

• Revises: ISO 14635-1:2000 - Gears — FZG test procedures — Part 1: FZG test method A/8,3/90 for relative scuffing load-carrying capacity of oils
• Effective Date: 19-Nov-2022

Standards Content (Sample)

FINAL
INTERNATIONAL ISO/FDIS
DRAFT
STANDARD 14635-1
ISO/TC 60/SC 2
Gears — FZG test procedures —
Secretariat: DIN
Voting begins on:
Part 1:
2023-03-17
FZG test method A/8,3/90 for relative
Voting terminates on:
scuffing load-carrying capacity of oils
2023-05-12
Engrenages — Méthodes d'essai FZG —
Partie 1: Méthode FZG A/8,3/90 pour évaluer la capacité de charge
au grippage des huiles
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
Reference number
BEING ACCEPTABLE FOR INDUSTRIAL, TECHNO-
ISO/FDIS 14635-1:2023(E)
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. © ISO 2023
---------------------- Page: 1 ----------------------
ISO/FDIS 14635-1:2023(E)
FINAL
INTERNATIONAL ISO/FDIS
DRAFT
STANDARD 14635-1
ISO/TC 60/SC 2
Gears — FZG test procedures —
Secretariat: DIN
Voting begins on:
Part 1:
FZG test method A/8,3/90 for relative
Voting terminates on:
scuffing load-carrying capacity of oils
Engrenages — Méthodes d'essai FZG —
Partie 1: Méthode FZG A/8,3/90 pour évaluer la capacité de charge
au grippage des huiles
COPYRIGHT PROTECTED DOCUMENT
© ISO 2023

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’s member body in the country of the requester.
RECIPIENTS OF THIS DRAFT ARE INVITED TO
ISO copyright office
SUBMIT, WITH THEIR COMMENTS, NOTIFICATION
OF ANY RELEVANT PATENT RIGHTS OF WHICH
CP 401 • Ch. de Blandonnet 8
THEY ARE AWARE AND TO PROVIDE SUPPOR TING
CH-1214 Vernier, Geneva
DOCUMENTATION.
Phone: [phone]
IN ADDITION TO THEIR EVALUATION AS
Reference number
Email: [e-mail]
BEING ACCEPTABLE FOR INDUSTRIAL, TECHNO-
ISO/FDIS 14635-1:2023(E)
Website: www.iso.org
LOGICAL, COMMERCIAL AND USER PURPOSES,
DRAFT INTERNATIONAL STANDARDS MAY ON
Published in Switzerland
OCCASION HAVE TO BE CONSIDERED IN THE
LIGHT OF THEIR POTENTIAL TO BECOME STAN-
DARDS TO WHICH REFERENCE MAY BE MADE IN
© ISO 2023 – All rights reserved
NATIONAL REGULATIONS. © ISO 2023
---------------------- Page: 2 ----------------------
ISO/FDIS 14635-1:2023(E)
Contents Page

Foreword ........................................................................................................................................................................................................................................iv

Introduction .................................................................................................................................................................................................................................v

1 Scope ................................................................................................................................................................................................................................. 1

2 Normative references ..................................................................................................................................................................................... 1

3 Terms and definitions .................................................................................................................................................................................... 1

4 Brief description of method ..................................................................................................................................................................... 2

4.1 General principle .................................................................................................................................................................................. 2

4.2 Precision ......... .................................................................................................................................. ............................................................ 4

5 Test materials ......................................................................................................................................................................................................... 4

5.1 Test gears ..................................................................................................................................................................................................... 4

5.2 Cleaning fluid ........................................................................................................................................................................................... 4

6 Apparatus .................................................................................................................................................................................................................... 6

6.1 FZG spur-gear test rig....................................................................................................................................................................... 6

6.2 Heating device ......................................................................................................................................................................................... 7

6.3 Revolution counter .............................................................................................................................................................................. 7

7 Preparation of apparatus ...........................................................................................................................................................................7

8 Test procedure .......................................................................................................................................................................................................8

9 Reporting of results ..........................................................................................................................................................................................9

Annex A (informative) Typical FZG test report sheet .....................................................................................................................10

Annex B (informative) Checklist for maintenance of FZG gear test rig .......................................................................11

Bibliography .............................................................................................................................................................................................................................16

iii
© ISO 2023 – All rights reserved
---------------------- Page: 3 ----------------------
ISO/FDIS 14635-1:2023(E)
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 documents 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).

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. Details of

any patent rights identified during the development of the document will be in the Introduction and/or

on the ISO list of patent declarations received (see www.iso.org/patents).

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 60, Gears, Subcommittee SC 2, Gear

capacity calculation.

This second edition cancels and replaces the first edition (ISO 14635-1:2000), of which it constitutes a

minor revision. The changes are as follows:

— ISO 1328-1:1995 has been dated as this document still refers to accuracy grade;

— replacement of ISO 4287 which has been withdrawn and replaced by ISO 21920-2;

— replacement of ISO 4964 which has been withdrawn and similar information can be found in

ISO 18265;

— replacement of some bibliography entries which were withdrawn, and changes from dated to

undated references;
— subclause 5.2, wording harmonized with the ISO 14635 series;

— Table 1, description "pitch line circumferential speed (v )" has been replaced by "circumferential

velocity at the pitch line" to harmonize the wording with the ISO 6336 series;

— Table 4, insertion of lines "Direction of rotation and Test lubrication volume" to conform to the

information in the ISO 14635 series.
A list of all parts in the ISO 14635 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.
1) Cancelled and replaced by ISO 1328-1:2013.
© ISO 2023 – All rights reserved
---------------------- Page: 4 ----------------------
ISO/FDIS 14635-1:2023(E)
Introduction

The types of gear failures which can be influenced by the lubricant in use are scuffing, low-speed wear

and the gear-surface fatigue phenomena known as micro- and macropitting. In the gear design process,

these gear damages are taken into consideration by the use of specific lubricant and service-related

characteristic values. For an accurate, field-related selection of these values, adequate lubricant test

procedures are required. The FZG test procedures described in this document and ISO 14635-2 and

ISO 14635-3, can be regarded as tools for the determination of the lubricant-related characteristic

values to be introduced into the load-carrying capacity calculation of gears.

FZG test method A/8,3/90 for the relative scuffing load-carrying capacity of oils described in this

document is typical for the majority of applications in industrial and marine gears. ISO 14635-2 is

related to the relative scuffing load-carrying capacity of oils of very high EP properties, as used for the

lubrication of automotive driveline components. Other FZG test procedures for the determination of

low-speed wear, micro- and macropitting load-carrying capacity of gears are intended to be added to

the ISO 14635 series as further parts.

2) FZG = Forschungsstelle für Zahnräder und Getriebebau, Technische Universität München (Gear Research

Centre,
© ISO 2023 – All rights reserved
---------------------- Page: 5 ----------------------
FINAL DRAFT INTERNATIONAL STANDARD ISO/FDIS 14635-1:2023(E)
Gears — FZG test procedures —
Part 1:
FZG test method A/8,3/90 for relative scuffing load-
carrying capacity of oils
1 Scope

This document specifies a test method based on a FZG four-square test machine to determine the

relative load-carrying capacity of lubricating oils defined by the gear-surface damage known as

scuffing. High surface temperatures due to high surface pressures and sliding velocities can initiate

the breakdown of the lubricant films. This test method can be used to assess such lubricant breakdown

under defined conditions of temperature, high sliding velocity and stepwise increased load.

NOTE This method is technically equivalent to ASTM D 5182-19 and CEC L-07-A-95.
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 1328-1:1995 , Cylindrical gears — ISO system of accuracy — Part : Definitions and allowable values of

deviations relevant to flanks of gear teeth
ISO 18265, Metallic materials — Conversion of hardness values

ISO 21920-2, Geometrical product specifications (GPS) — Surface texture: Profile — Part 2: Terms,

definitions and surface texture parameters

ASTM D 235, Specification for Mineral Spirits (Petroleum Spirits) (Hydrocarbon Dry Cleaning Solvent)

3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.

ISO and IEC maintain terminology 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
scuffing load-carrying capacity

(of a lubricant) maximum load which can be sustained under a defined set of conditions

Note 1 to entry: For examples of failure see Figure 1.
3) Cancelled and replaced by ISO 1328-1:2013.
© ISO 2023 – All rights reserved
---------------------- Page: 6 ----------------------
ISO/FDIS 14635-1:2023(E)

Note 2 to entry: Scuffing is a particularly severe form of damage to the gear-tooth surface in which seizure or

welding together of areas of tooth surface occur, due to absence or breakdown of a lubricant film between the

contacting tooth flanks of mating gears, typically caused by high temperature and high pressure. Scuffing is

most likely when surface velocities are high. Scuffing can also occur at relatively low sliding velocities when

tooth-surface pressures are high enough either generally or, because of uneven surface geometry and loading, in

discrete areas.

Note 3 to entry: Risk of scuffing damage varies with the properties of gear materials, the lubricant used, the

surface roughness of tooth flanks, the sliding velocities and the load. Consequences of scuffing of high-speed

gears include a tendency to high levels of dynamic loading due to increase of vibrations, which usually leads to

further damage by scuffing, pitting or tooth breakage.
3.2
FZG test condition A/8,3/90

test condition where A is the particular tooth form of the test gears, according to Table 1, 8,3 is the

speed at the pitch circle, in metres per second, and 90 is the initial oil temperature in degrees Celsius,

from load stage 5 and onward in the oil sump

Note 1 to entry: The direction of the rotation of the gears is shown in Figure 3.

3.3
failure load stage

load stage in which the summed total width of scuffing damage on the active flank area of the 16 pinion

teeth exceeds one gear-tooth width, i.e. 20 mm

Note 1 to entry: Examples of flank damages for the purpose of the test method are shown in Figure 1.

4 Brief description of method
4.1 General principle

A set of test gears as defined in Clause 5, Tables 1 and 2, is run with the test lubricant at constant speed

for a fixed number of revolutions using dip-lubrication mode. Loading of the gear teeth is increased in

steps outlined in Table 3. Beginning with load stage 5, the initial oil temperature is controlled between

(90 ± 3) °C. During the test run of each load stage, the oil temperature is allowed to rise freely. After

load stage 4, the pinion tooth flanks are inspected for surface damage at the end of each load stage and

any changes in appearance are noted. A test is considered complete when either the failure criteria has

been met or when load stage 12 is run without meeting the failure criteria.

It is the responsibility of the operator to ensure that all local legislative and statutory requirements are

met.

NOTE It has been assumed by the compilers of this test method that anyone using the method will either

be fully trained and familiar with all normal engineering and laboratory practice, or will be under the direct

supervision of such a person.

WARNING — When the rig is running, there are long loaded shafts and highly stressed test gears

turning at high speed and precautions shall be taken to protect personnel.
Protection from noise is also highly recommended.
© ISO 2023 – All rights reserved
---------------------- Page: 7 ----------------------
ISO/FDIS 14635-1:2023(E)
a) No failure marks b) No failure marks
c) Approx. 5 mm failure marks d) Approx. 15 mm failure marks
e) 20 mm failure marks f) Approx. 2 mm failure marks
g) Approx. 6 mm failure marks h) 20 mm failure marks
© ISO 2023 – All rights reserved
---------------------- Page: 8 ----------------------
ISO/FDIS 14635-1:2023(E)

NOTE This figure describes the typical pinion tooth flank changes occurring in FZG tests. Changes in the

original surface condition (criss-cross grinding) can be described by their physical appearance. One and the

same type of flank damage can be described in different places in the world by using different terminology (e.g.

"scuffing", "scoring" and "severe wear"). In order to avoid misinterpretation of the pinion tooth flank changes

occurring during the test, typical examples of non-failure and failure are given.

NOTE The colours represented in the electronic file of this document can be neither viewed nor printed

as true representations. Only copies of this document printed by ISO can be guaranteed to represent the true

colours.
Figure 1 — FZG A-type gear-tooth face changes (flank damages)
4.2 Precision

The precision of the method has been evaluated according to ISO 5725-2 with three oils (two reference

oils and one oil from the market). The failure load stage of these oils covered the range 5 to 12 inclusive.

Values of repeatability, r, and reproducibility, R, as defined in ISO 5725-2, for this test procedure are:

r = 1 load stage
R = 2 load stages

NOTE The above precision results apply to the range of failure load stages 5 to 12.

5 Test materials
5.1 Test gears

A pair of type “A” gears with a specification according to Tables 1 and 2 shall be used for testing. Each

pair of test gears may be used twice for testing, using both tooth flanks as load-carrying flanks.

5.2 Cleaning fluid
Petroleum spirit conforming to ASTM D 235 shall be used.
Table 1 — Details of FZG test gears type A
Dimension Symbol Numerical value Unit
Shaft centre distance a 91,5 mm
Effective tooth width b 20 mm
Working pitch diameter pinion d 73,2 mm
wheel d 109,8 mm
Tip diameter pinion d 88,77 mm
wheel d 112,5 mm
Module m 4,5 mm
Number of teeth pinion z 16
wheel z 24
Profile-shift coefficient pinion x 0,853 2
wheel x - 0,50
Pressure angle α 20 °
Working pressure angle α 22,5 °
F = normal tooth load in N (see Table 3).
© ISO 2023 – All rights reserved
---------------------- Page: 9 ----------------------
ISO/FDIS 14635-1:2023(E)
TTabablele 1 1 ((ccoonnttiinnueuedd))
Dimension Symbol Numerical value Unit
Circumferential velocity at the pitch line v 8,3 m/s
Addendum engagement pinion e 14,7 mm
wheel e 3,3 mm
Sliding speed at tooth tip pinion v 5,56 m/s
ga1
wheel v 1,25 m/s
ga2
Specific sliding at tooth tip pinion ζ 0,86
wheel ζ 0,34
Specific sliding at tooth root pinion ζ - 0,52
wheel ζ - 5,96
Hertzian contact pressure p N/mm
14,7⋅ F
F = normal tooth load in N (see Table 3).
...

ISO/FDIS 14635-1:2023(E)
ISO /TC 60/SC 2
Secretariat: DIN
Date: 2023-01-2503-03
Gears — FZG test procedures —
Part 1:
FZG test method A/8,3/90 for relative scuffing load-carrying
capacity of oils
Engrenages — Méthodes d'essai FZG —

Partie 1: Méthode FZG A/8,3/90 pour évaluer la capacité de charge au grippage des huiles

FDIS stage
© ISO 2023 – All rights reserved
---------------------- Page: 1 ----------------------
ISO/FDIS 14635-1:2023(E)
© ISO 2023

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’s member body in the country of the requester.

ISO copyright office
CP 401 • Ch. de Blandonnet 8
CH-1214 Vernier, Geneva
Phone: + 41 22 749 01 11
EmailE-mail: [e-mail]
Website: www.iso.orgwww.iso.org
Published in Switzerland
ii © ISO 2023 – All rights reserved
---------------------- Page: 2 ----------------------
ISO/FDIS 14635-1:2023(E)
Contents

Foreword ............................................................................................................................................................................................. v

Introduction ......................................................................................................................................................................................vi i

Part 1: FZG test method A/8,3/90 for relative scuffing load-carrying capacity of oils ....................................... 1

1 Scope ....................................................................................................................................................................................... 1

2 Normative references ....................................................................................................................................................... 1

3 Terms and definitions ...................................................................................................................................................... 1

4 Brief description of method ........................................................................................................................................... 2

4.1 General principle ................................................................................................................................................................ 2

4.2 Precision ................................................................................................................................................................................ 5

5 Test materials ...................................................................................................................................................................... 5

5.1 Test gears .............................................................................................................................................................................. 5

5.2 Cleaning fluid ....................................................................................................................................................................... 5

6 Apparatus .............................................................................................................................................................................. 9

6.1 FZG spur-gear test rig ....................................................................................................................................................... 9

6.2 Heating device .................................................................................................................................................................. 10

6.3 Revolution counter ......................................................................................................................................................... 11

7 Preparation of apparatus ............................................................................................................................................. 11

8 Test procedure ................................................................................................................................................................. 11

9 Reporting of results........................................................................................................................................................ 12

Annex A (informative) Typical FZG test report sheet ................................................................................................... 14

Annex B (informative) Checklist for maintenance of FZG gear test rig ................................................................. 16

Bibliography .................................................................................................................................................................................... 22

Foreword v
Introduction vii
1 Scope 1
2 Normative references 1
3 Terms and definitions 1
4 Brief description of method 2
4.1 General principle 2
4.2 Precision 4
5 Test materials 4
5.1 Test gears 4
5.2 Cleaning fluid 4
6 Apparatus 7
6.1 FZG spur-gear test rig 7
6.2 Heating device 8
6.3 Revolution counter 8
7 Preparation of apparatus 8
8 Test procedure 9
© ISO 2023 – All rights reserved iii
---------------------- Page: 3 ----------------------
ISO/FDIS 14635-1:2023(E)
9 Reporting of results 9
Annex A (informative) Typical FZG test report sheet 11
Annex B (informative) Checklist for maintenance of FZG gear test rig 12
B.1 How to recognize malfunction 12
B.1.1 Distribution of scuffing marks 12
B.1.2 Tooth contact pattern 12
B.1.3 Tests with reference oil 12
B.1.4 Other indications 12
B.2 Parts that need maintenance 12
B.2.1 Test-gear box 12
B.2.1.1 Shafts 12
B.2.1.2 Bearings 13
B.2.1.3 Keys 13
B.2.1.4 Spacer rings 13
B.2.1.5 Gear box and front cover 13
B.2.1.6 Seals 13
B.2.2 Connecting shafts and flanges 13
B.2.2.1 Load coupling 13
B.2.2.2 Torque-measuring device 13
B.2.2.3 Load coupling support bearing 13
B.2.2.4 Torsion shaft 14
B.2.2.5 Flanges 14
B.2.3 Slave-gear box 14
B.2.3.1 Slave gears 14
B.2.3.2 Lubrication 14
B.2.4 Other parts 14
B.2.4.1 Heating 14
B.2.4.2 Flexible coupling blocks 14
B.2.4.3 Motor 14
B.3 Approximate time intervals 14
Bibliography 16
iv © ISO 2023 – All rights reserved
---------------------- Page: 4 ----------------------
ISO/FDIS 14635-1:2023(E)
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 documents should be noted. This document was drafted in accordance with the

editorial rules of the ISO/IEC Directives, Part 2 (see www.iso.org/directiveswww.iso.org/directives).

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. Details of any

patent rights identified during the development of the document will be in the Introduction and/or on

the ISO list of patent declarations received (see www.iso.org/patentswww.iso.org/patents).

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 60, Gears, Subcommittee SC 2, Gear

capacity calculation.

This second edition cancels and replaces the first edition (ISO 14635-1:2000), of which it constitutes a

minor revision in accordance with ISO Directives, Part 1.. The changes are as follows:

The main changes are as follows:

— — ISO 1328-1:1995, Cylindrical gears — ISO system of accuracy — Part 1: Definitions and allowable

values of deviations relevant to corresponding flanks of gear teeth has been dated as this document

still refers to accuracy grade;

— — replacement of ISO 4287, Geometrical Product Specifications (GPS) — Surface texture: Profile

method — Terms, definitions and surface texture parameters which has been withdrawn and replaced

by ISO 21920-2, Geometrical product specifications (GPS) — Surface texture: Profile — Part 2: Terms,

definitions and surface texture parameters;

— — replacement of ISO 4964, Steel — Hardness conversions which has been withdrawn and similar

information can be found in ISO 18265, Metallic materials — Conversion of hardness values;

— — updatingreplacement of some bibliography entries which were withdrawn, and changes from

dated to undated references where no specific reason requires the dated reference (see Bibliography

footnotes);;

— — Clause 5.2,subclause 5.2, wording harmonized withinwith the ISO 14635 series;

— — Table 1,Table 1, description "pitch line circumferential speed (vw))" has been replaced by

"circumferential velocity at the pitch line" to harmonize the wording with the ISO 6336- series.;

Cancelled and replaced by ISO 1328-1:2013.
© ISO 2023 – All rights reserved v
---------------------- Page: 5 ----------------------
ISO/FDIS 14635-1:2023(E)

— — Table 4,Table 4, insertion of lines "Direction of rotation and Test lubrication volume" to conform

to be compliant with giventhe information withinin the ISO 14635 series.
A list of all parts in the ISO 14635 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.htmlwww.iso.org/members.html.
vi © ISO 2023 – All rights reserved
---------------------- Page: 6 ----------------------
ISO/FDIS 14635-1:2023(E)
Introduction

The types of gear failures which can be influenced by the lubricant in use are scuffing, low-speed wear

and the gear-surface fatigue phenomena known as micro- and macropitting. In the gear design process,

these gear damages are taken into consideration by the use of specific lubricant and service-related

characteristic values. For an accurate, field-related selection of these values, adequate lubricant test

procedures are required. The FZG test procedures described in this document and other parts of

ISO 14635-2 and ISO 14635-3, can be regarded as tools for the determination of the lubricant-related

characteristic values to be introduced into the load-carrying capacity calculation of gears.

FZG test method A/8,3/90 for the relative scuffing load-carrying capacity of oils described in this part of

ISO 14635document is typical for the majority of applications in industrial and marine gears. ISO 14635-

2 is related to the relative scuffing load-carrying capacity of oils of very high EP properties, as used for

the lubrication of automotive driveline components. Other FZG test procedures for the determination of

low-speed wear, micro- and macropitting load-carrying capacity of gears are already in a late state of

development. They canintended to be added later to the ISO 14635 series as further parts.

FZG = Forschungsstelle für Zahnräder und Getriebebau, Technische Universität München (Gear Research Centre,

© ISO 2023 – All rights reserved vii
---------------------- Page: 7 ----------------------
ISO/FDIS 14635-1:2023(E)
Gears — FZG test procedures —
Part 1:
FZG test method A/8,3/90 for relative scuffing load-carrying
capacity of oils
1 Scope

This document specifies a test method based on a FZG four-square test machine to determine the relative

load-carrying capacity of lubricating oils defined by the gear-surface damage known as scuffing. High

surface temperatures due to high surface pressures and sliding velocities can initiate the breakdown of

the lubricant films. This test method can be used to assess such lubricant breakdown under defined

conditions of temperature, high sliding velocity and stepwise increased load.
4 5

NOTE This method is technically equivalent to ASTM D 5182-97 , DIN 51354-1 and DIN 51354-2 ,

IP 334/90 19 and CEC L-07-A-95.
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 1328-1:1995 , Cylindrical gears — ISO system of accuracy — Part : Definitions and allowable values of

deviations relevant to flanks of gear teeth

ISO 5725-2, Accuracy (trueness and precision) of measurement methods and results — Part 2: Basic method

for the determination of repeatability and reproducibility of a standard measurement method

ISO 18265, Metallic materials — Conversion of hardness values

ISO 21920-2, Geometrical product specifications (GPS) — Surface texture: Profile — Part 2: Terms,

definitions and surface texture parameters

ASTM D 235, Specification for Mineral Spirits (Petroleum Spirits) (Hydrocarbon Dry Cleaning Solvent)

3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.

ISO and IEC maintain terminology databases for use in standardization at the following addresses:

— ISO Online browsing platform: available at https://www.iso.org/obp
Field Code Changed
— IEC Electropedia: available at https://www.electropedia.org/
Field Code Changed
3.1
scuffing load-carrying capacity

(of a lubricant) maximum load which can be sustained under a defined set of conditions

Note 1 to entry: For examples of failure see Figure 1.Figure 1.

FZG = Forschungsstelle für Zahnräder und Getriebebau, Technische Universität München (Gear Research Centre,

Technical University, Munich), Boltzmannstraße 15, D-85748 Garching, Germany.
ASTM D 5182-97 has been replaced by ASTM D 5182-19.
DIN 51354-1 and DIN 51354-2 have been replaced by DIN ISO 14635-1.
IP 334/90 has been withdrawn.
Cancelled and replaced by ISO 1328-1:2013.
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ISO/FDIS 14635-1:2023(E)

Note 2 to entry: Scuffing is a particularly severe form of damage to the gear-tooth surface in which seizure or

welding together of areas of tooth surface occur, due to absence or breakdown of a lubricant film between the

contacting tooth flanks of mating gears, typically caused by high temperature and high pressure. Scuffing is most

likely when surface velocities are high. Scuffing can also occur at relatively low sliding velocities when tooth-surface

pressures are high enough either generally or, because of uneven surface geometry and loading, in discrete areas.

Note 3 to entry: Risk of scuffing damage varies with the properties of gear materials, the lubricant used, the surface

roughness of tooth flanks, the sliding velocities and the load. Consequences of scuffing of high-speed gears include

a tendency to high levels of dynamic loading due to increase of vibrations, which usually leads to further damage by

scuffing, pitting or tooth breakage.
3.2
FZG test condition A/8,3/90

test condition where A is the particular tooth form of the test gears, according to Table 1;Table 1, 8,3 is

the speed at the pitch circle, in metres per second, and 90 is the initial oil temperature, in degrees Celsius,

from load stage 5 and onward in the oil sump

Note 1 to entry: The direction of the rotation of the gears is shown in Figure 3.Figure 3.

3.3
failure load stage

load stage in which the summed total width of scuffing damage on the active flank area of the 16 pinion

teeth exceeds one gear-tooth width, i.e. 20 mm

Note 1 to entry: Examples of flank damages for the purpose of the test method are shown in Figure 1.Figure 1.

4 Brief description of method
4.1 General principle

A set of test gears as defined in Clause 5, Tables 1Clause 5, Tables 1 and 2,2, is run with the test lubricant

at constant speed for a fixed number of revolutions using dip-lubrication mode. Loading of the gear teeth

is increased in steps outlined in Table 3.Table 3. Beginning with load stage 5, the initial oil temperature

is controlled between (90 ± 3) °C. During the test run of each load stage, the oil temperature is allowed to

rise freely. After load stage 4, the pinion tooth flanks are inspected for surface damage at the end of each

load stage and any changes in appearance are noted. A test is considered complete when either the failure

criteria has been met or when load stage 12 is run without meeting the failure criteria.

It is the responsibility of the operator to ensure that all local legislative and statutory requirements are

met.

NOTE It has been assumed by the compilers of this test method that anyone using the method will either be

fully trained and familiar with all normal engineering and laboratory practice, or will be under the direct

supervision of such a person.

WARNING — When the rig is running, there are long loaded shafts and highly stressed test gears

turning at high speed and precautions shall be taken to protect personnel.
Protection from noise is also highly recommended.
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ISO/FDIS 14635-1:2023(E)

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a) No failure marks b) No failure marks

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c) Approx. 5 mm failure marks d) Approx. 15 mm failure marks
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ISO/FDIS 14635-1:2023(E)

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e) 20 mm failure marks f) Approx. 2 mm failure marks

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g) Approx. 6 mm failure marks h) 20 mm failure marks

NOTE This figure describes the typical pinion tooth flank changes occurring in FZG tests. Changes in the

original surface condition (criss-cross grinding) can be described by their physical appearance. One and the same

type of flank damage can be described in different places in the world by using different terminology (e.g. "scuffing",

"scoring" and "severe wear"). In order to avoid misinterpretation of the pinion tooth flank changes occurring during

the test, typical examples of non-failure and failure are given.

PRODUCTION NOTE The colours represented in the electronic file of this part of ISO 14635document can be

neither viewed nor printed as true representations. Only copies of this part of ISO 14635document printed by ISO

can be guaranteed to represent the true colours.
Figure 1 — FZG A-type gear-tooth face changes (flank damages)
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ISO/FDIS 14635-1:2023(E)
4.2 Precision

The precision of the method has been evaluated according to ISO 5725-2 with three oils (two reference

oils and one oil from the market). The failure load stage of these oils covered the range 5 to 12 inclusive.

Values of repeatability, r, and reproducibility, R, as defined in ISO 5725-2, for this test procedure are:

r = 1 load stage
R = 2 load stages

NOTE The above precision results apply to the range of failure load stages 5 to 12.

5 Test materials
5.1 Test gears

A pair of type “A” gears with a specification according to Tables 1Tables 1 and 22 shall be used for testing.

Each pair of test gears may be used twice for testing, utilizingusing both tooth flanks as load-carrying

flanks.
5.2 Cleaning fluid
Petroleum spirit conforming to ASTM D 235 shall be used.
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ISO/FDIS 14635-1:2023(E)
Table 1 — Details of FZG test gears type A
Dimension Symbol Numerical value Unit
Shaft centre distance a 91,5 mm
Effective tooth width b 20 mm
Working pitch diameter pinion dw1 73,2 mm
wheel dw2 109,8 mm
Tip diameter pinion d 88,77 mm
wheel da2 112,5 mm
Module m 4,5 mm
Number of teeth pinion z1 16
wheel z2 24
Profile-shift coefficient pinion x 0,853 2
wheel x2 - 0,50
Pressure angle α 20 °
Working pressure angle αw 22,5 °
Circumferential velocity at the pitch line vw 8,3 m/s
Addendum engagement pinion e 14,7 mm
wheel ea2 3,3 mm
Sliding speed at tooth tip pinion vga1 5,56 m/s
wheel vga2 1,25 m/s
Specific sliding at tooth tip pinion ζE1 0,86
wheel ζ 0,34
Specific sliding at tooth root pinion ζA1 - 0,52
wheel ζE2 - 5,96
Hertzian contact pressure p N/mm
c 14,7∙�𝐹𝐹 ⋅�𝐹𝐹 P
nt nt
Fnt = normal tooth load in N (see Table 3).Table 3).
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ISO/FDIS 14635-1:2023(E)
Table 2 — Manufacturing details of FZG test gears type A
Case-hardening steel with restricted hardenability to 2/3 of the lower
scatter band. Material composition:
C = 0,13 % to 0,20 % Mo = max. 0,12 %
Material
Si = max. 0,40 % Ni = max. 0,30 %
Mn = 1,00 % to 1,30 % Al = 0,02 % to 0,05 %
P = max. 0,025 % B = 0,001 % to 0,003 %
Case-hardening steel with Cu = max. 0,30 %
Inserted Cells
restricted hardenability to 2/3
of the lower scatter band.
Material composition:
C = 0,13 % to 0,20 %
Mo = max. 0,12 %
Si = max. 0,40 %
Ni = max. 0,30 %
Material
Merged Cells
Mn = 1,00 % to 1,30 %
Al = 0,02 % to 0,05 %
P = max. 0,025 %
B = 0,001 % to
0,003 %
S = 0,020 % to 0,035 %
Cu = max. 0,30 %
Cr = 0,80 % to 1,30 %
Cr = 0,80 % to 1,30 %
The test gears are carburized and case hardened. The case depth at a
hardness of 550 HV10 shall be 0,6 mm to 0,9 mm. The surface hardness
after tempering: 60 HRC to 62 HRC, core strength in tooth root centre:
Heat treatment
2 2
1 000 N/mm to 1 250 N/mm (determined in accordance with ISO 18265
based on Brinell hardness).
Retained austenite should be nominally 20 %.
Gear accuracy grade Q5 according to ISO 1328-1:1995

Arithmetic roughness of flanks Ra Ra is separately determined for left and right flanks, measured each at

three flanks per gear across the centre of the tooth parallel to the pitch line;
measuring parameters according toin accordance with ISO 21920-2
measured length l = 4,8 mm,
:cut-off length λ = 0,8 mm;
velocity = 0,5 mm/s, using a skid.
measured length lt = 4,8 mm;
cut-off length λc = 0,8 mm;
velocity = 0,5 mm/s, using a skid.
Average roughness (relating to manufacture batches of a minimum of a 100
gear sets).
Average roughness (relating to manufacture
batches of a minimum of a 100 gear sets)
Pinion:
Inserted Cells
Pinion: Ra = 0,35 μm ± 0,1 μm
Gear:
Inserted Cells
Gear: Ra = 0,30 μm ± 0,1 μm
Maximum roughness (average of three measurements according to the
described method and valid for 95 of 100 tested gears).
Pinion and gear: Ra = 0,5 μm
Pinion and gear: Ra = 0,5 μm
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ISO/FDIS 14635-1:2023(E)
Maag criss-cross grinding (15° method), 154 r/min of generating stroke
Grinding
drive
Flank modification None
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ISO/FDIS 14635-1:2023(E)
76 Apparatus
7.16.1 FZG spur-gear test rig

6.1.1 The FZG spur-gear test machine utilizesuses a recirculating power loop principle, also known as

a four-square configuration, to provide a fixed torque (load) to a pair of precision test gears. A schematic

view of the test rig is shown in Figures 2 and 3.Figures 2 and 3. The slave gearbox and the test gearbox

are connected through two torsional shafts. Shaft 1 contains a load coupling used to apply the torque

through the use of known weights defined in Table 3Table 3 hung on the loading arm.

6.1.2 The test gearbox contains heating elements to maintain and control the minimum temperature of

the oil. A temperature sensor located in the side of the test gearbox is used to control the heating system

as required by the test operating conditions.

6.1.3 The test machine is powered by an electric motor of minimum 5,5 kW at a speed of approximately

1 450 r/min.

6.1.4 A check list for maintenance of the FZG gear test rig is given for information in Annex B.Annex B.

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Key
1 6
Testtest wheel Drivedrive motor
2 Viewview A 7 Loadload coupling
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ISO/FDIS 14635-1:2023(E)
3 Testtest pinion 8 Shaft 1shaft 1 (two pieces)
4 Torquetorque measuring coupling 9 Slaveslave gears
5 Shaft 2shaft 2 (torsion shaft) 10 torsion shaft outer tube
Figure 2 — Schematic section of the FZG gear test machine

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Key
Testtest wheel
Deleted Cells
Testtest pinion
Deleted Cells
Activeactive tooth flank

Figure 3 — Mounting of the FZG test gears of type A (view A of Figure 2)Figure 2)

7.26.2 Heating device

A suitable oven or heating device is required to warm the test gears to 60 °C to 80 °C for assembling on

the shafts.
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ISO/FDIS 14635-1:2023(E)
7.36.3 Revolution counter

A suitable counter shall be used to control the number of revolutions during each load stage of the test.

The counter should be capable of shutting down the test machine at the appropriate number of

revolutions.
87 Preparation of apparatus

7.1 Flush the test gear case twice with petroleum spirit, ensuring that the bearings are cleared of any

previous oil, and air dry with a water-free air line.

7.2 Clean the test gears in petroleum spirit and air dry, using finger stalls or gloves.

7.3 With the unaided eye, inspect the gears for corrosion, rust or any other damage. Reject the gears if

so damaged.

7.4 Heat both the gears to between 60 °C and max. 80 °C, with an appropriate heating device.

7.5 Assemble the test gear box (except the top cover) with the test pinion on shaft 1 (right-hand side)

and the test gear on shaft 2 (left-hand side) as shown in Figure 2.Figure 2. Ensure that the test pinion and

test wheel are correctly aligned, i.e. no offset.
7.6 Check that the switch drain cock is in the CLOSED position.
7.7 Fill the test gear box with a nominal 1,25 litrel of test oil.
7.8 Plug in the heater.
7.9 Fit and secure the top cover to the test gear box.

7.10 Apply load stage 12 using the 0,5 m radius position (see Table 3)Table 3) for 2 min to 3 min

without running the motor, in order to bring the test gears and the clearances in the system into the

correct working position.
98 Test procedure

8.1 Apply the first load stage (see Table 3).Table 3). Using the conditions given in Table 4,Table 4, start

the motor, switch on the heater and run for 21 700 revolutions of the motor (approximately

15 minutesmin) according to Table 4.Table 4.

8.2 Stop the motor and apply the load for stage 2. Restart and run according to Table 4Table 4 for

21 700 revolutions of the motor. Repeat for load stages 3 and 4.
8.3 At the end of load stage 4, inspect
...