ISO 12129-1:2019

Plain bearings — Tolerances — Part 1: Fits

This document specifies a system of fits applicable to metallic plain bearings used in general engineering for mean relative bearing clearances, ψm, of 0,56 ? up to 3,15 ?. Other clearance ranges can be used depending upon the requirements in specific applications. This system of fits is not applicable to half‑bearings and bushes which, due to their special characteristics, are not measured by diameter but by wall thickness, and which are dimensionally changed on assembly. It is not applicable to profile bore or tilting pad bearings, or to cases where specific tolerances have been established by consideration of the bearing performance at both extremes of clearance. This document is applicable preferably to rotating machine parts and shafting, but it can be used similarly in other ranges of application.

Paliers lisses — Tolérances — Partie 1: Ajustements

Drsni ležaji - Tolerance - 1. del: Ujemi

Ta dokument določa sistem prileganja, ki se uporablja za kovinske drsne ležaje, ki se uporabljajo v splošni tehniki, za srednje relativne zračnosti ležajev, ψm, od 0,56 ? do 3,15 ?. V primerih posebnih uporab se lahko glede na posebne zahteve uporabijo tudi drugi razponi ohlapnosti.
Ta sistem prilegov se ne uporablja za polovične ležaje in puše, ki se zaradi svojih posebnih značilnosti ne merijo s premerom, temveč z debelino stene, in katerih dimenzije se pri montaži (sestavi) spremenijo. Ne uporablja se za ležaje s profilno odprtino ali samoprilagodljive segmentne ležaje ali za primere, kjer so bile določene posebne tolerance z upoštevanjem zmogljivosti ležaja pri obeh skrajnih vrednostih ohlapnostih.
Ta dokument se prednostno uporablja za dele rotacijskih strojev in gredi, vendar se lahko podobno uporablja tudi na drugih področjih uporabe.

General Information

• Status: Published
• Publication Date: 19-Mar-2019
• ICS: 21.100.10 - Plain bearings
• Technical Committee: ISO/TC 123/SC 3 - Dimensions, tolerances and construction details
• Drafting Committee: ISO/TC 123/SC 3 - Dimensions, tolerances and construction details
• Ref Project: SIST ISO 12129-1:2023 - Plain bearings - Tolerances - Part 1: Fits

Relations

• Revises: ISO 12129-1:1995 - Plain bearings — Part 1: Fits
• Effective Date: 02-Jun-2018

Standards Content (Sample)

SLOVENSKI STANDARD
SIST ISO 12129-1:2023
01-april-2023
Drsni ležaji - Tolerance - 1. del: Ujemi
Plain bearings - Tolerances - Part 1: Fits
Paliers lisses - Tolérances - Partie 1: Ajustements
Ta slovenski standard je istoveten z: ISO 12129-1:2019
ICS:
21.100.10 Drsni ležaji Plain bearings
SIST ISO 12129-1:2023 en,fr,de
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

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SIST ISO 12129-1:2023

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SIST ISO 12129-1:2023
INTERNATIONAL ISO
STANDARD 12129-1
Second edition
2019-03
Plain bearings — Tolerances —
Part 1:
Fits
Paliers lisses — Tolérances —
Partie 1: Ajustements
Reference number
ISO 12129-1:2019(E)
©
ISO 2019

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SIST ISO 12129-1:2023
ISO 12129-1:2019(E)

COPYRIGHT PROTECTED DOCUMENT
© ISO 2019
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: [phone]
Fax: [phone]
Email: [e-mail]
Website: www.iso.org
Published in Switzerland
ii © ISO 2019 – All rights reserved

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SIST ISO 12129-1:2023
ISO 12129-1:2019(E)

Contents Page
Foreword .iv
Introduction .v
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 System of fits . 1
5 Mean relative bearing clearance . 2
6 Tolerance intervals. 2
6.1 Tolerance . 2
6.2 Fundamental deviation . 2
6.3 Number . 3
6.4 Symbol . 3
7 Ranges of nominal dimensions . 3
8 Limit deviations . 3
9 Minimum and maximum clearances. 3
10 Example . 3
Bibliography .10
© ISO 2019 – All rights reserved iii

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SIST ISO 12129-1:2023
ISO 12129-1:2019(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 123, Plain bearings, Subcommittee SC 3,
Dimensions, tolerances and construction details.
This second edition cancels and replaces the first edition (ISO 12129-1:1995), which has been technically
revised. The main changes compared to the previous edition are as follows:
— the title has been improved;
— normative references have been updated;
— Table 1 has been corrected;
— Table 2 has been added.
A list of all parts in the ISO 12129 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.
iv © ISO 2019 – All rights reserved

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SIST ISO 12129-1:2023
ISO 12129-1:2019(E)

Introduction
This document has been established because it is not possible to use the ISO deviations given in
ISO 286-1 and ISO 286-2 to develop clearance fits which correspond to the requirements of plain bearing
engineering for approximately uniform mean relative bearing clearances for all nominal size ranges.
© ISO 2019 – All rights reserved v

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SIST ISO 12129-1:2023

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SIST ISO 12129-1:2023
INTERNATIONAL STANDARD ISO 12129-1:2019(E)
Plain bearings — Tolerances —
Part 1:
Fits
1 Scope
This document specifies a system of fits applicable to metallic plain bearings used in general engineering
for mean relative bearing clearances, ψ , of 0,56 ‰ up to 3,15 ‰. Other clearance ranges can be used
m
depending upon the requirements in specific applications.
This system of fits is not applicable to half-bearings and bushes which, due to their special characteristics,
are not measured by diameter but by wall thickness, and which are dimensionally changed on assembly.
It is not applicable to profile bore or tilting pad bearings, or to cases where specific tolerances have
been established by consideration of the bearing performance at both extremes of clearance.
This document is applicable preferably to rotating machine parts and shafting, but it can be used
similarly in other ranges of application.
2 Normative references
There are no normative references in this document.
3 Terms and definitions
No terms and definitions are listed in this document.
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 http: //www .electropedia .org/
4 System of fits
The system of fits specified in this document is a normal system of fits, in which the fundamental
deviation H of the bearing bore diameter is in accordance with ISO 286-2. The tolerance interval of the
shaft is correlated to correspond to the mean relative bearing clearance, ψ .
m
© ISO 2019 – All rights reserved 1

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SIST ISO 12129-1:2023
ISO 12129-1:2019(E)

5 Mean relative bearing clearance
The mean relative bearing clearance, ψ , in per thousand (‰), of a range of nominal dimensions is
m
given by Formula (1):
C
D,m
ψ = (1)
m
D
m
where C is the mean absolute bearing diametral clearance, in micrometres.
D,m
C + C
D,maxmD, in
C = (2)
D,m
2
where
C is the maximum value of the absolute bearing diametral clearance;
D,max
C is the minimum value of the absolute bearing diametral clearance;
D,min
D is the arithmetic mean of the range of nominal dimensions, in millimetres.
m
EXAMPLE
For the nominal dimension range from 250 mm to 280 mm, the arithmetic mean of the range of nominal
dimensions is given by
250+280
D = mm=265mm
m
2
For ψ = 1,6 ‰, Table 1 and Formula (2) lead then to the mean bearing diametral clearance
m
0,,466+0382
C = mm=0,424mm
D,m
2
and to the mean relative bearing clearance
0,424
ψ = = 1,6 ‰
m
265
6 Tolerance intervals
6.1 Tolerance
The tolerance is chosen so that, for a uniform mean relative bearing clearance, ψ , in each case from
m
the minimum to the maximum range of nominal dimensions, an approximately uniform maximum
deviation from the relative bearing clearance within a tolerance interval is not exceeded. The lower
limit is dictated by economy and methods of production.
The tolerance interval of the shaft in each case is smaller by one IT grade (basic tolerance grade in
accordance with ISO 286-1) than the tolerance interval of the correlated bearing bore.
6.2 Fundamental deviation
The fundamental deviation is determined by the mean relative bearing clearance, ψ .
m
2 © ISO 2019 – All rights reserved

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SIST ISO 12129-1:2023
ISO 12129-1:2019(E)

6.3 Number
Each of the following values of ψ , in per thousand, corresponds to one tolerance interval:
m
— 0,56;
— 0,8;
— 1,12;
— 1,32;
— 1,6;
— 1,9;
— 2,24;
— 3,15.
6.4 Symbol
The symbol for the mean relative bearing clearance is ψ . If Greek letters are not available, the symbol
m
*
C may be used instead of the Greek letter ψ.
7 Ranges of nominal dimensions
The ranges of nominal dimensions are more closely stepped than in ISO 286-2 so that the maximum
deviation from the mean relative bearing clearance, ψ , can be more closely adhered to.
m
8 Limit deviations
The limit deviations for the shafts are given in Table 1.
9 Minimum and maximum clearances
The minimum and maximum clearances between the shaft and bearing bore, together with the limit
deviations for the shaft which are required for the calculation of the plain bearings, are
...

INTERNATIONAL ISO
STANDARD 12129-1
Second edition
2019-03
Plain bearings — Tolerances —
Part 1:
Fits
Paliers lisses — Tolérances —
Partie 1: Ajustements
Reference number
ISO 12129-1:2019(E)
©
ISO 2019

---------------------- Page: 1 ----------------------
ISO 12129-1:2019(E)

COPYRIGHT PROTECTED DOCUMENT
© ISO 2019
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: [phone]
Fax: [phone]
Email: [e-mail]
Website: www.iso.org
Published in Switzerland
ii © ISO 2019 – All rights reserved

---------------------- Page: 2 ----------------------
ISO 12129-1:2019(E)

Contents Page
Foreword .iv
Introduction .v
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 System of fits . 1
5 Mean relative bearing clearance . 2
6 Tolerance intervals. 2
6.1 Tolerance . 2
6.2 Fundamental deviation . 2
6.3 Number . 3
6.4 Symbol . 3
7 Ranges of nominal dimensions . 3
8 Limit deviations . 3
9 Minimum and maximum clearances. 3
10 Example . 3
Bibliography .10
© ISO 2019 – All rights reserved iii

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ISO 12129-1:2019(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 123, Plain bearings, Subcommittee SC 3,
Dimensions, tolerances and construction details.
This second edition cancels and replaces the first edition (ISO 12129-1:1995), which has been technically
revised. The main changes compared to the previous edition are as follows:
— the title has been improved;
— normative references have been updated;
— Table 1 has been corrected;
— Table 2 has been added.
A list of all parts in the ISO 12129 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.
iv © ISO 2019 – All rights reserved

---------------------- Page: 4 ----------------------
ISO 12129-1:2019(E)

Introduction
This document has been established because it is not possible to use the ISO deviations given in
ISO 286-1 and ISO 286-2 to develop clearance fits which correspond to the requirements of plain bearing
engineering for approximately uniform mean relative bearing clearances for all nominal size ranges.
© ISO 2019 – All rights reserved v

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INTERNATIONAL STANDARD ISO 12129-1:2019(E)
Plain bearings — Tolerances —
Part 1:
Fits
1 Scope
This document specifies a system of fits applicable to metallic plain bearings used in general engineering
for mean relative bearing clearances, ψ , of 0,56 ‰ up to 3,15 ‰. Other clearance ranges can be used
m
depending upon the requirements in specific applications.
This system of fits is not applicable to half-bearings and bushes which, due to their special characteristics,
are not measured by diameter but by wall thickness, and which are dimensionally changed on assembly.
It is not applicable to profile bore or tilting pad bearings, or to cases where specific tolerances have
been established by consideration of the bearing performance at both extremes of clearance.
This document is applicable preferably to rotating machine parts and shafting, but it can be used
similarly in other ranges of application.
2 Normative references
There are no normative references in this document.
3 Terms and definitions
No terms and definitions are listed in this document.
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 http: //www .electropedia .org/
4 System of fits
The system of fits specified in this document is a normal system of fits, in which the fundamental
deviation H of the bearing bore diameter is in accordance with ISO 286-2. The tolerance interval of the
shaft is correlated to correspond to the mean relative bearing clearance, ψ .
m
© ISO 2019 – All rights reserved 1

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ISO 12129-1:2019(E)

5 Mean relative bearing clearance
The mean relative bearing clearance, ψ , in per thousand (‰), of a range of nominal dimensions is
m
given by Formula (1):
C
D,m
ψ = (1)
m
D
m
where C is the mean absolute bearing diametral clearance, in micrometres.
D,m
C + C
D,maxmD, in
C = (2)
D,m
2
where
C is the maximum value of the absolute bearing diametral clearance;
D,max
C is the minimum value of the absolute bearing diametral clearance;
D,min
D is the arithmetic mean of the range of nominal dimensions, in millimetres.
m
EXAMPLE
For the nominal dimension range from 250 mm to 280 mm, the arithmetic mean of the range of nominal
dimensions is given by
250+280
D = mm=265mm
m
2
For ψ = 1,6 ‰, Table 1 and Formula (2) lead then to the mean bearing diametral clearance
m
0,,466+0382
C = mm=0,424mm
D,m
2
and to the mean relative bearing clearance
0,424
ψ = = 1,6 ‰
m
265
6 Tolerance intervals
6.1 Tolerance
The tolerance is chosen so that, for a uniform mean relative bearing clearance, ψ , in each case from
m
the minimum to the maximum range of nominal dimensions, an approximately uniform maximum
deviation from the relative bearing clearance within a tolerance interval is not exceeded. The lower
limit is dictated by economy and methods of production.
The tolerance interval of the shaft in each case is smaller by one IT grade (basic tolerance grade in
accordance with ISO 286-1) than the tolerance interval of the correlated bearing bore.
6.2 Fundamental deviation
The fundamental deviation is determined by the mean relative bearing clearance, ψ .
m
2 © ISO 2019 – All rights reserved

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ISO 12129-1:2019(E)

6.3 Number
Each of the following values of ψ , in per thousand, corresponds to one tolerance interval:
m
— 0,56;
— 0,8;
— 1,12;
— 1,32;
— 1,6;
— 1,9;
— 2,24;
— 3,15.
6.4 Symbol
The symbol for the mean relative bearing clearance is ψ . If Greek letters are not available, the symbol
m
*
C may be used instead of the Greek letter ψ.
7 Ranges of nominal dimensions
The ranges of nominal dimensions are more closely stepped than in ISO 286-2 so that the maximum
deviation from the mean relative bearing clearance, ψ , can be more closely adhered to.
m
8 Limit deviations
The limit deviations for the shafts are given in Table 1.
9 Minimum and maximum clearances
The minimum and maximum clearances between the shaft and bearing bore, together with the limit
deviations for the shaft which are required for the calculation of the plain bearings, are given in Table 1.
The corresponding tolerance intervals of the relative bearing clearance are given in Table 2.
10 Example
Shaft fit dimension 200 mm for a mean bearing clearance ψ = 1,12 ‰.
m
Preferred form:
∅200
ψ 1,12
Alternative form where Greek letters are not available:
∅200
C* 1,12
Alternative form where subscripts are not available:
*
∅200 (C 1,12)
© ISO 2019 – All rights reserved 3

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