EN ISO 286-1:2010

SLOVENSKI STANDARD
01-december-2010
1DGRPHãþD
SIST EN 20286-1:2000
SIST ISO 1829:1999
SIST ISO 286-1:1999
6SHFLILNDFLMDJHRPHWULMVNLKYHOLþLQL]GHOND7ROHUDQþQLVLVWHP,62]DGROåLQVNH
PHUHGHO2VQRYD]DWROHUDQFHRGVWRSDQMDLQXMHPH,62
Geometrical product specifications (GPS) - ISO code system for tolerances on linear
sizes - Part 1: Basis of tolerances, deviations and fits (ISO 286-1:2010)
Geometrische Produktspezifikation (GPS) - ISO-Toleranzsystem für Längenmaße - Teil
1: Grundlagen für Toleranzen, Abmaße und Passungen (ISO 286-1:2010)
Spécification géométrique des produits (GPS) - Systeme de codification ISO pour les
tolérances sur les tailles linéaires - Partie 1: Base des tolérances, écarts et ajustements
(ISO 286-1:2010)
Ta slovenski standard je istoveten z: EN ISO 286-1:2010
ICS:
17.040.10 Tolerance in ujemi Limits and fits
17.040.40 6SHFLILNDFLMDJHRPHWULMVNLK Geometrical Product
YHOLþLQL]GHOND*36 Specification (GPS)
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

EUROPEAN STANDARD
EN ISO 286-1
NORME EUROPÉENNE
EUROPÄISCHE NORM
April 2010
ICS 17.040.10 Supersedes EN 20286-1:1993
English Version
Geometrical product specifications (GPS) - ISO code system for
tolerances on linear sizes - Part 1: Basis of tolerances,
deviations and fits (ISO 286-1:2010)
Spécification géométrique des produits (GPS) - Système Geometrische Produktspezifikation (GPS) - ISO-
de codification ISO pour les tolérances sur les tailles Toleranzsystem für Längenmaße - Teil 1: Grundlagen für
linéaires - Partie 1: Base des tolérances, écarts et Toleranzen, Abmaße und Passungen (ISO 286-1:2010)
ajustements (ISO 286-1:2010)
This European Standard was approved by CEN on 6 February 2010.

CEN members are bound to comply with the CEN/CENELEC Internal Regulations which stipulate the conditions for giving this European
Standard the status of a national standard without any alteration. Up-to-date lists and bibliographical references concerning such national
standards may be obtained on application to the CEN Management Centre or to any CEN member.

This European Standard exists in three official versions (English, French, German). A version in any other language made by translation
under the responsibility of a CEN member into its own language and notified to the CEN Management Centre has the same status as the
official versions.
CEN members are the national standards bodies of Austria, Belgium, Bulgaria, Croatia, Cyprus, Czech Republic, Denmark, Estonia,
Finland, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland,
Portugal, Romania, Slovakia, Slovenia, Spain, Sweden, Switzerland and United Kingdom.

EUROPEAN COMMITTEE FOR STANDARDIZATION
COMITÉ EUROPÉEN DE NORMALISATION

EUROPÄISCHES KOMITEE FÜR NORMUNG

Management Centre: Avenue Marnix 17, B-1000 Brussels
© 2010 CEN All rights of exploitation in any form and by any means reserved Ref. No. EN ISO 286-1:2010: E
worldwide for CEN national Members.

Contents Page
Foreword .3

Foreword
This document (EN ISO 286-1:2010) has been prepared by Technical Committee ISO/TC 213 "Dimensional
and geometrical product specifications and verification" in collaboration with Technical Committee
CEN/TC 290 “Dimensional and geometrical product specification and verification” the secretariat of which is
held by AFNOR.
This European Standard shall be given the status of a national standard, either by publication of an identical
text or by endorsement, at the latest by October 2010, and conflicting national standards shall be withdrawn at
the latest by October 2010.
Attention is drawn to the possibility that some of the elements of this document may be the subject of patent
rights. CEN [and/or CENELEC] shall not be held responsible for identifying any or all such patent rights.
This document supersedes EN 20286-1:1993.
According to the CEN/CENELEC Internal Regulations, the national standards organizations of the following
countries are bound to implement this European Standard: Austria, Belgium, Bulgaria, Croatia, Cyprus, Czech
Republic, Denmark, Estonia, Finland, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia,
Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Romania, Slovakia, Slovenia, Spain,
Sweden, Switzerland and the United Kingdom.
Endorsement notice
The text of ISO 286-1:2010 has been approved by CEN as a EN ISO 286-1:2010 without any modification.

INTERNATIONAL ISO
STANDARD 286-1
Second edition
2010-04-15
Geometrical product specifications
(GPS) — ISO code system for tolerances
on linear sizes —
Part 1:
Basis of tolerances, deviations and fits
Spécification géométrique des produits (GPS) — Système de
codification ISO pour les tolérances sur les tailles linéaires —
Partie 1: Base des tolérances, écarts et ajustements

Reference number
ISO 286-1:2010(E)
©
ISO 2010
ISO 286-1:2010(E)
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ii © ISO 2010 – All rights reserved

ISO 286-1:2010(E)
Contents Page
Foreword .iv
Introduction.v
1 Scope.1
2 Normative references.1
3 Terms and definitions .1
3.1 Basic terminology .2
3.2 Terminology related to tolerances and deviations .2
3.3 Terminology related to fits .5
3.4 Terminology related to the ISO fit system .9
4 ISO code system for tolerances on linear sizes.11
4.1 Basic concepts and designations .11
4.2 Designation of the tolerance class (writing rules) .13
4.3 Determination of the limit deviations (reading rules).14
4.4 Selection of tolerance classes .26
5 ISO fit system.26
5.1 General .26
5.2 Generics of fits .27
5.3 Determination of a fit.27
Annex A (informative) Further information about the ISO system of limits and fits and former
practice.29
Annex B (informative) Examples of the use of ISO 286-1 to determine fits and tolerance classes .31
Annex C (informative) Relationship to the GPS matrix model .36
Bibliography.38

ISO 286-1:2010(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.
International Standards are drafted in accordance with the rules given in the ISO/IEC Directives, Part 2.
The main task of technical committees is to prepare International Standards. Draft International Standards
adopted by the technical committees are circulated to the member bodies for voting. Publication as an
International Standard requires approval by at least 75 % of the member bodies casting a vote.
Attention is drawn to the possibility that some of the elements of this document may be the subject of patent
rights. ISO shall not be held responsible for identifying any or all such patent rights.
ISO 286-1 was prepared by Technical Committee ISO/TC 213, Dimensional and geometrical product
specifications and verification.
This second edition of ISO 286-1 cancels and replaces ISO 286-1:1988 and ISO 1829:1975, which have been
technically revised.
ISO 286 consists of the following parts, under the general title Geometrical product specifications (GPS) —
ISO code system for tolerances on linear sizes:
⎯ Part 1: Basis of tolerances, deviations and fits
⎯ Part 2: Tables of standard tolerance grades and limit deviations for holes and shafts
iv © ISO 2010 – All rights reserved

ISO 286-1:2010(E)
Introduction
This International Standard is a geometrical product specification (GPS) standard and is to be regarded as a
general GPS standard (see ISO/TR 14638). It influences chain links 1 and 2 of the chain of standards on size
in the general GPS matrix.
For more detailed information on the relation of this part of ISO 286 to the GPS matrix model, see Annex C.
The need for limits and fits for machined workpieces was brought about mainly by the requirement for
interchange ability between mass produced parts and the inherent inaccuracy of manufacturing methods,
coupled with the fact that “exactness” of size was found to be unnecessary for the most workpiece features. In
order that fit function could be satisfied, it was found sufficient to manufacture a given workpiece so that its
size lay within two permissible limits, i.e. a tolerance, this being the variation in size acceptable in manufacture
while ensuring the functional fit requirements of the product.
Similarly, where a specific fit condition is required between mating features of two different workpieces, it is
necessary to ascribe an allowance, either positive or negative, to the nominal size to achieve the required
clearance or interference. This part of ISO 286 gives the internationally accepted code system for tolerances
on linear sizes. It provides a system of tolerances and deviations suitable for two features of size types:
“cylinder” and “two parallel opposite surfaces”. The main intention of this code system is the fulfilment of the
function fit.
The terms “hole”, “shaft” and “diameter” are used to designate features of size type cylinder (e.g. for the
tolerancing of diameter of a hole or shaft). For simplicity, they are also used for two parallel opposite surfaces
(e.g. for the tolerancing of thickness of a key or width of a slot).
The pre-condition for the application of the ISO code system for tolerances on linear sizes for the features
forming a fit is that the nominal sizes of the hole and the shaft are identical.
The previous edition of ISO 286-1 (published in 1988) had the envelope criterion as the default association
criterion for the size of a feature of size; however, ISO 14405-1 changes this default association criterion to
the two-point size criterion. This means that form is no longer controlled by the default specification of size.
In many cases, the diameter tolerances according to this part of ISO 286 are not sufficient for an effective
control of the intended function of the fit. The envelope criterion according to ISO 14405-1 may be required. In
addition, the use of geometrical form tolerances and surface texture requirements may improve the control of
the intended function.
INTERNATIONAL STANDARD ISO 286-1:2010(E)

Geometrical product specifications (GPS) — ISO code system
for tolerances on linear sizes —
Part 1:
Basis of tolerances, deviations and fits
1 Scope
This part of ISO 286 establishes the ISO code system for tolerances to be used for linear sizes of features of
the following types:
a) cylinder;
b) two parallel opposite surfaces.
It defines the basic concepts and the related terminology for this code system. It provides a standardized
selection of tolerance classes for general purposes from amongst the numerous possibilities.
Additionally, it defines the basic terminology for fits between two features of size without constraints of
orientation and location and explains the principles of “basic hole” and “basic shaft”.
2 Normative references
The following referenced documents are indispensable for the application of this document. For dated
references, only the edition cited applies. For undated references, the latest edition of the referenced
document (including any amendments) applies.
1)
ISO 286-2 , Geometrical product specifications (GPS) — ISO code system for tolerances on linear sizes —
Part 2: Tables of standard tolerance grades and limit deviations for holes and shafts
ISO 14405-1, Geometrical product specifications (GPS) — Dimensional tolerancing — Part 1: Linear sizes
ISO 14660-1:1999, Geometrical Product Specifications (GPS) — Geometrical features — Part 1: General
terms and definitions
ISO 14660-2:1999, Geometrical Product Specifications (GPS) — Geometrical features — Part 2: Extracted
median line of a cylinder and a cone, extracted median surface, local size of an extracted feature
3 Terms and definitions
For the purposes of this document, the terms and definitions given in ISO 14405-1 and ISO 14660-1 and the
following apply. It should be noted, however, that some of the terms are defined in a more restricted sense
than in common usage.
1) To be published. (Revision of ISO 286-2:1988)
ISO 286-1:2010(E)
3.1 Basic terminology
3.1.1
feature of size
geometrical shape defined by a linear or angular dimension which is a size
[ISO 14660-1:1999, definition 2.2]
NOTE 1 The feature of size can be a cylinder, a sphere, two parallel opposite surfaces.
NOTE 2 In former editions of international standards, such as ISO 286-1 and ISO/R 1938, the meanings of the terms
“plain workpiece” and “single features” are close to that of “feature of size”.
NOTE 3 For the purpose of ISO 286, only features of size type cylinder as well as type-two parallel opposite surfaces,
defined by a linear dimension, apply.
3.1.2
nominal integral feature
theoretically exact integral feature as defined by a technical drawing or by other means
[ISO 14660-1:1999, definition 2.3]
3.1.3
hole
internal feature of size of a workpiece, including internal features of size which are not cylindrical
NOTE See also Introduction.
3.1.4
basic hole
hole chosen as a basis for a hole-basis fit system
NOTE 1 See also 3.4.1.1.
NOTE 2 For the purpose of the ISO code system, a basic hole is a hole for which the lower limit deviation is zero.
3.1.5
shaft
external feature of size of a workpiece, including external features of size which are not cylindrical
NOTE See also Introduction.
3.1.6
basic shaft
shaft chosen as a basis for a shaft-basis fit system
NOTE 1 See also 3.4.1.2.
NOTE 2 For the purposes of the ISO code system, a basic shaft is a shaft for which the upper limit deviation is zero.
3.2 Terminology related to tolerances and deviations
3.2.1
nominal size
size of a feature of perfect form as defined by the drawing specification
See Figure 1.
NOTE 1 Nominal size is used for the location of the limits of size by the application of the upper and lower limit
deviations.
NOTE 2 In former times, this was referred to as “basic size”.
2 © ISO 2010 – All rights reserved

ISO 286-1:2010(E)
3.2.2
actual size
size of the associated integral feature
NOTE 1 “Associated integral feature” is defined in ISO 14660-1:1999, 2.6.
NOTE 2 The actual size is obtained by measurement.
3.2.3
limits of size
extreme permissible sizes of a feature of size
NOTE To fulfil the requirement, the actual size shall lie between the upper and lower limits of size; the limits of size
are also included.
3.2.3.1
upper limit of size
ULS
largest permissible size of a feature of size
See Figure 1.
3.2.3.2
lower limit of size
LLS
smallest permissible size of a feature of size
See Figure 1.
3.2.4
deviation
value minus its reference value
NOTE For size deviations, the reference value is the nominal size and the value is the actual size.
3.2.5
limit deviation
upper limit deviation or lower limit deviation from nominal size
3.2.5.1
upper limit deviation
ES (to be used for internal features of size)
es (to be used for external features of size)
upper limit of size minus nominal size
See Figure 1.
NOTE Upper limit deviation is a signed value and may be negative, zero or positive.
ISO 286-1:2010(E)
Key
1 tolerance interval
2 sign convention for deviations
a
Nominal size.
b
Upper limit of size.
c
Lower limit of size.
d
Upper limit deviation.
e
Lower limit deviation (in this case also fundamental deviation).
f
Tolerance.
NOTE The horizontal continuous line, which limits the tolerance interval, represents the fundamental deviations for a
hole. The dashed line, which limits the tolerance interval, represents the other limit deviation for a hole.
Figure 1 — Illustration of definitions (a hole is used in the example)
3.2.5.2
lower limit deviation
EI (to be used for internal features of size)
ei (to be used for external features of size)
lower limit of size minus nominal size
See Figure 1.
NOTE Lower limit deviation is a signed value and may be negative, zero or positive.
3.2.6
fundamental deviation
limit deviation that defines the placement of the tolerance interval in relation to the nominal size
NOTE 1 The fundamental deviation is that limit deviation, which defines that limit of size which is the nearest to the
nominal size (see Figure 1 and 4.1.2.5).
NOTE 2 The fundamental deviation is identified by a letter (e.g. B, d).
4 © ISO 2010 – All rights reserved

ISO 286-1:2010(E)
3.2.7
∆ value
variable value added to a fixed value to obtain the fundamental deviation of an internal feature of size
See Table 3.
3.2.8
tolerance
difference between the upper limit of size and the lower limit of size
NOTE 1 The tolerance is an absolute quantity without sign.
NOTE 2 The tolerance is also the difference between the upper limit deviation and the lower limit deviation.
3.2.8.1
tolerance limits
specified values of the characteristic giving upper and/or lower bounds of the permissible value
3.2.8.2
standard tolerance
IT
any tolerance belonging to the ISO code system for tolerances on linear sizes
NOTE The letters in the abbreviated term “IT” stand for “International Tolerance”.
3.2.8.3
standard tolerance grade
group of tolerances for linear sizes characterized by a common identifier
NOTE 1 In the ISO code system for tolerances on linear sizes, the standard tolerance grade identifier consists of IT
followed by a number (e.g. IT7); see 4.1.2.3.
NOTE 2 A specific tolerance grade is considered as corresponding to the same level of accuracy for all nominal sizes.
3.2.8.4
tolerance interval
variable values of the size between and including the tolerance limits
NOTE 1 The former term “tolerance zone”, which was used in connection with linear dimensioning (according to
ISO 286-1:1988), has been changed to “tolerance interval” since an interval refers to a range on a scale whereas a
tolerance zone in GPS refers to a space or an area, e.g. tolerancing according to ISO 1101.
NOTE 2 For the purpose of ISO 286, the interval is contained between the upper and the lower limits of size. It is
defined by the magnitude of the tolerance and its placement relative to the nominal size (see Figure 1).
NOTE 3 The tolerance interval does not necessarily include the nominal size (see Figure 1). Tolerance limits may be
two-sided (values on both sides of the nominal size) or one-sided (both values on one side of the nominal size). The case
where the one tolerance limit is on one side, the other limit value being zero, is a special case of a one-sided indication.
3.2.8.5
tolerance class
combination of a fundamental deviation and a standard tolerance grade
NOTE In the ISO code system for tolerances on linear sizes, the tolerance class consists of the fundamental
deviation identifier followed by the tolerance grade number (e.g. D13, h9, etc.), see 4.2.1.
3.3 Terminology related to fits
The concepts in this clause relate only to nominal features of size (perfect form). For the model definition of a
nominal feature of size, see ISO 17450-1:—, 3.18.
For the determination of a fit, see 5.3.
ISO 286-1:2010(E)
3.3.1
clearance
difference between the size of the hole and the size of the shaft when the diameter of the shaft is smaller than
the diameter of the hole
NOTE In the calculation of clearance, the obtained values are positive (see B.2).
3.3.1.1
minimum clearance
〈in a clearance fit〉 difference between the lower limit of size of the hole and the upper limit of size of the shaft
See Figure 2.
3.3.1.2
maximum clearance
〈in a clearance or transition fit〉 difference between the upper limit of size of the hole and the lower limit of size
of the shaft
See Figures 2 and 4.
3.3.2
interference
difference before mating between the size of the hole and the size of the shaft when the diameter of the shaft
is larger than the diameter of the hole
NOTE In the calculation of an interference, the obtained values are negative (see B.2).
3.3.2.1
minimum interference
〈in an interference fit〉 difference between the upper limit of size of the hole and the lower limit of size of the
shaft
See Figure 3.
3.3.2.2
maximum interference
〈in an interference or transition fit〉 difference between the lower limit of size of the hole and the upper limit of
size of the shaft
See Figures 3 and 4.
3.3.3
fit
relationship between an external feature of size and an internal feature of size (the hole and shaft of the same
type) which are to be assembled
3.3.3.1
clearance fit
fit that always provides a clearance between the hole and shaft when assembled, i.e. the lower limit of size of
the hole is either larger than or, in the extreme case, equal to the upper limit of size of the shaft
See Figure 2.
3.3.3.2
interference fit
fit that always provides an interference between the hole and the shaft when assembled, i.e. the upper limit of
size of the hole is either smaller than or, in the extreme case, equal to the lower limit of size of the shaft
See Figure 3.
6 © ISO 2010 – All rights reserved

ISO 286-1:2010(E)
3.3.3.3
transition fit
fit which may provide either a clearance or an interference between the hole and the shaft when assembled
See Figure 4.
NOTE In a transition fit, the tolerance intervals of the hole and the shaft overlap either completely or partially;
therefore, if there is a clearance or an interference depends on the actual sizes of the hole and the shaft.

Key
1 tolerance interval of the hole
2 tolerance interval of the shaft, case 1: when the upper limit of size of the shaft is lower than the lower limit of size of
the hole, the minimum clearance is larger than zero
3 tolerance interval of the shaft, case 2: when the upper limit of size of the shaft is identical to the lower limit of size of
the hole, the minimum clearance is zero
a
Minimum clearance.
b
Maximum clearance.
c
Nominal size = lower limit of size of the hole.
NOTE The horizontal continuous wide lines, which limit the tolerance intervals, represent the fundamental deviations.
The dashed lines, which limit the tolerance intervals, represent the other limit deviations.
Figure 2 — Illustration of definitions of a clearance fit (nominal model)
ISO 286-1:2010(E)
Key
1 tolerance interval of the hole
2 tolerance interval of the shaft, case 1: when the lower limit of size of the shaft is identical to the upper limit of size of
the hole, the minimum interference is zero
3 tolerance interval of the shaft, case 2: when the lower limit of size of the shaft is larger than the upper limit of size of
the hole, the minimum interference is larger than zero
a
Maximum interference.
b
Minimum interference.
c
Nominal size = lower limit of size of the hole.
NOTE The horizontal continuous wide lines, which limit the tolerance intervals, represent the fundamental deviations.
The dashed lines, which limit the tolerance intervals, represent the other limit deviations.
Figure 3 — Illustration of definitions of an interference fit (nominal model)
8 © ISO 2010 – All rights reserved

ISO 286-1:2010(E)
Key
1 tolerance interval of the hole
2-4 tolerance interval of the shaft (some possible placements are shown)
a
Maximum clearance.
b
Maximum interference.
c
Nominal size = lower limit of size of the hole.
NOTE The horizontal continuous wide lines, which limit the tolerance intervals, represent the fundamental deviations.
The dashed lines, which limit the tolerance intervals, represent the other limit deviations.
Figure 4 — Illustration of definitions of a transition fit (nominal model)
3.3.4
span of a fit
arithmetic sum of the size tolerances on two features of size comprising the fit
See Figure B.1.
NOTE 1 The span of a fit is an absolute value without sign and expresses the possible nominal variation of the fit.
NOTE 2 The span of a clearance fit is the difference between the maximum and minimum clearances. The span of an
interference fit is the difference between the maximum and minimum interferences. The span of a transition fit is the sum
of the maximum clearance and maximum interference (see Annex B).
3.4 Terminology related to the ISO fit system
3.4.1
ISO fit system
system of fits comprising shafts and holes toleranced by the ISO code system for tolerances on linear sizes
NOTE The pre-condition for the application of the ISO code system for tolerances on linear sizes for the features
forming a fit is that the nominal sizes of the hole and the shaft are identical.
3.4.1.1
hole-basis fit system
fits where the fundamental deviation of the hole is zero, i.e. the lower limit deviation is zero
See Figure 5.
ISO 286-1:2010(E)
NOTE A fit system in which the lower limit of size of the hole is identical to the nominal size. The required clearances
or interferences are obtained by combining shafts of various tolerance classes with basic holes of a tolerance class with a
fundamental deviation of zero.
3.4.1.2
shaft-basis fit system
fits where the fundamental deviation of the shaft is zero, i.e. the upper limit deviation is zero
See Figure 6.
NOTE A fit system in which the upper limit of size of the shaft is identical to the nominal size. The required
clearances or interferences are obtained by combining holes of various tolerance classes with basic shafts of a tolerance
class with a fundamental deviation of zero.

Key
1 basic hole “H”
2 tolerance interval of the basic hole
3 tolerance interval of the different shafts
a
Nominal size.
NOTE 1 The horizontal continuous lines, which limit the tolerance intervals, represent the fundamental deviations for a
basic hole and different shafts.
NOTE 2 The dashed lines, which limit the tolerance intervals, represent the other limit deviations.
NOTE 3 The figure shows the possibility of combinations between a basic hole and different shafts, related to their
standard tolerance grades.
NOTE 4 Possible examples of hole-basis fits are: H7/h6, H6/k5, H6/p4.
Figure 5 — Hole-basis fit system
10 © ISO 2010 – All rights reserved

ISO 286-1:2010(E)
Key
1 basic shaft “h”
2 tolerance interval of the basic shaft
3 tolerance interval of the different holes
a
Nominal size.
NOTE 1 The horizontal continuous lines, which limit the tolerance intervals, represent the fundamental deviations for a
basic shaft and different holes.
NOTE 2 The dashed lines, which limit the tolerance intervals, represent the other limit deviations.
NOTE 3 The figure shows the possibility of combinations between a basic shaft and different holes, related to their
standard tolerance grades.
NOTE 4 Possible examples of shaft-basis fits are: h6/G7, h6/H6, h6/M6.
Figure 6 — Shaft-basis fit system
4 ISO code system for tolerances on linear sizes
4.1 Basic concepts and designations
4.1.1 Relation to ISO 14405-1
A feature of size may be toleranced by using the ISO code system defined in this part of ISO 286 or by using
+ and − tolerancing according to ISO 14405-1. Both indications are equivalent.
x
EXAMPLE 1 32 y is equivalent to 32 “code”
where
32 is the nominal size, in millimeters;
x is the upper tolerance limit (x can be positive, zero or negative);
y is the lower tolerance limit (y can be positive, zero or negative);
“code” is the tolerance class according to 4.2.1.
ISO 286-1:2010(E)
If a fit shall be toleranced, the envelope requirement according to ISO 14405-1 may be indicated (see A.2).
x
EXAMPLE 2 32 y is equivalent to 32 “code”
4.1.2 Tolerance class
4.1.2.1 General
The tolerance class contains information on the magnitude of the tolerance and the position of the tolerance
interval relative to the nominal size of the feature of size.
4.1.2.2 Magnitude of the tolerance
The tolerance class expresses the magnitude of the tolerance. The magnitude of the tolerance is a function of
the standard tolerance grade number and the nominal size of the toleranced feature.
4.1.2.3 Standard tolerance grades
The standard tolerance grades are designated by the letters IT followed by the grade number, e.g. IT7.
Values of standardised tolerances are given in Table 1. Each of the columns gives the values of the
tolerances for one standard tolerance grade between standard tolerance grades IT01 and IT18 inclusive.
Each row in Table 1 is representing one range of sizes. The limits of the ranges of sizes are given in the first
column of Table 1.
NOTE 1 When the standard tolerance grade is associated with a letter or letters representing a fundamental deviation
to form a tolerance class, the letters IT are omitted, e.g. H7.
NOTE 2 From IT6 to IT18, the standard tolerances are multiplied by the factor 10 at each fifth step. This rule applies to
all standard tolerances and may be used to extrapolate values for IT grades not given in Table 1.
EXAMPLE For the nominal size range 120 mm up to and including 180 mm, the value of IT20 is:
IT20 = IT15 × 10 = 1,6 mm × 10 = 16 mm
4.1.2.4 Placement of tolerance interval
The tolerance interval (former term: tolerance zone) is a variable value contained between the upper and the
lower limits of size. The tolerance class expresses the position of the tolerance interval relative to the nominal
size, by means of the fundamental deviation. The information on the position of the tolerance interval, i.e. on
the fundamental deviation, is identified by one or more letters, called the fundamental deviation identifiers:
A graphical overview of the position of the tolerance intervals relative to the nominal sizes and the signs
(+ or −) of the fundamental deviations for holes and shafts are given in Figures 7, 8 and 9.
4.1.2.5 Fundamental deviation
The fundamental deviation is that limit deviation, which defines that limit of size, which is the nearest to the
nominal size (see Figure 7).
The fundamental deviations are identified and controlled by:
⎯ upper case letter(s) for holes (A . . . ZC), see Tables 2 and 3;
⎯ lower case letter(s) for shafts (a . . . zc), see Tables 4 and 5.
12 © ISO 2010 – All rights reserved

ISO 286-1:2010(E)
NOTE 1 To avoid confusion, the following letters are not used: I, i; L, l; O, o; Q, q; W, w.
NOTE 2 The fundamental deviations are not defined individually for each specific nominal size, but for ranges of
nominal sizes as given in Tables 2 to 5.
The fundamental deviation in micrometres is a function of the identifier (letter) and the nominal size of the
toleranced feature.
Tables 2 and 3 contain the signed values of the fundamental deviations for hole tolerances. Tables 4 and 5
contain the signed values of the fundamental deviations for shaft tolerances.
The sign + is used when the tolerance limit identified by the fundamental deviation is above nominal size and
the sign − is used when the tolerance limit identified by the fundamental deviation is below nominal size.
Each of the columns in Tables 2 to 5 gives the values of the fundamental deviation for one fundamental
deviation identifier letter. Each of the rows is representing one range of sizes. The limits of the ranges of sizes
are given in the first column of the tables.
The other limit deviation (upper or lower) is established from the fundamental deviation and the standard
tolerance (IT) as shown in Figures 8 and 9.
NOTE 3 The concept of fundamental deviations does not apply to JS and js. Their tolerance limits are distributed
symmetrically about the nominal size line (see Figures 8 and 9).
NOTE 4 The ranges of sizes in Tables 2 to 5 are in many cases (for deviations a to c and r to zc or A to C and R to ZC)
subdivisions of the main ranges of Table 1.
The last six columns on the right side of Table 3 contain a separate table with ∆-values. ∆ is a function of the
tolerance grade and the nominal size of the toleranced feature. It is only relevant for deviations K to ZC and
for standard tolerance grades IT3 to IT7/IT8.
The value of ∆ shall be added to the fixed value given in the main table, whenever +∆ is indicated, to form the
correct value of the fundamental deviation.
4.2 Designation of the tolerance class (writing rules)
4.2.1 General
The tolerance class shall be designated by the combination of an upper-case letter(s) for holes and lower-
case letters for shafts identifying the fundamental deviation and by the number representing the standard
tolerance grade.
EXAMPLE H7 (holes), h7 (shafts).
4.2.2 Size and its tolerance
A size and its tolerance shall be designated by the nominal size followed by the designation of the required
tolerance class, or shall be designated by the nominal size followed by + and/or − limit deviations
(see ISO 14405-1).
ISO 286-1:2010(E)
In the following examples the indicated limit deviations are equivalent to the indicated tolerance classes.
EXAMPLE 1
ISO 286 ISO 14405-1
+0,025
32 H7 ≡
80 js15 ≡ 80 ± 0,6
−0,012
≡
100 g6
100−0,034
NOTE When using + or − tolerancing determined from a tolerance class, the tolerance class may be added in
brackets for auxiliary information purposes and vice versa.
+0,025 +0,025
( )
EXAMPLE 2 32 H7 0 32 0 (H7)
4.2.3 Determination of a tolerance class
Determination of a tolerance class is derived from fit requirements (clearances, interferences), see 5.3.4.
4.3 Determination of the limit deviations (reading rules)
4.3.1 General
The determination of the limit deviations for a given toleranced size, e.g. the transformation of a tolerance
class into + and − tolerancing can be performed by the use of:
⎯ the Tables 1 to 5 of this part of ISO 286 (see 4.3.2); or
⎯ the tables of ISO 286-2 (see 4.3.3). Only selected cases are covered.
4.3.2 Determination of limit deviations using the tables of this part of ISO 286
4.3.2.1 General
The tolerance class is decomposed into the fundamental deviation identifier and the standard tolerance grade
number.
EXAMPLE Toleranced size for a hole 90 F7 and for a shaft 90 f7
where
90 is the nominal size in millimetres;
F is the fundamental deviation identifier for a hole;
f is the fundamental deviation identifier for a shaft;
7 is the standard tolerance grade number;
is the envelope requirement according to ISO 14405-1 (if necessary).
4.3.2.2 Standard tolerance grade
From the standard tolerance grade number, the standard tolerance grade (ITx) is obtained.
From the nominal size and the standard tolerance grade the magnitude of the tolerance, e.g. the standard
tolerance value is obtained by the use of Table 1.
14 © ISO 2010 – All rights reserved

ISO 286-1:2010(E)
EXAMPLE 1 Toleranced size for a hole 90 F7 and for a shaft 90 f7
The standard tolerance grade number is “7”, hence, the standard tolerance grade is IT7.
The standard tolerance value has to be taken from Table 1 in the line of the nominal size range above 80 mm up to and
including 120 mm and in the column of the standard tolerance grade IT7.
Consequently, the standard tolerance value is: 35 µm.
EXAMPLE 2 Toleranced size for a hole 28 P9
The standard tolerance grade number is “9”, hence, the standard tolerance grade is IT9.
The standard tolerance value has to be taken from Table 1 in the line of the nominal size range above 18 mm up to and
including 30 mm and in the column of the standard tolerance grade IT9.
Consequently the standard tolerance value is: 52 µm.
4.3.2.3 Position of the tolerance interval
From the nominal size and the fundamental deviation identifier the fundamental deviation ( the upper or lower
limit deviation) is obtained by use of Tables 2 and 3 for holes (upper-case letters) and Tables 4 and 5 for
shafts (lower-case letters).
EXAMPLE 1 Toleranced size for a hole 90 F7
The fundamental deviation identifier is “F”, hence, this is a hole case and Table 2 applies.
From Table 2, line “80 to 100” and column “F”, the lower limit deviation EI is: +36 µm.
EXAMPLE 2 Toleranced size for a shaft 90 f7
The fundamental deviation identifier is “f”, hence, this is a shaft case and Table 4 applies.
From Table 4, line “80 to 100” and column “f”, the upper limit deviation es is: −36 µm.
EXAMPLE 3 Toleranced size for a hole 28 P9
The fundamental deviation identifier is “P”, hence, this is a hole case and Table 3 applies.
From Table 3, line “24 to 30” and column “P”, the upper limit deviation ES is: −22 µm.
4.3.2.4 Establishment of limit deviations
One of the limit deviations (upper or lower) has already been determined in 4.3.2.3. The other limit deviations
(upper or lower) are obtained by calculation according to the formulae given in Figures 8 and 9 and using the
standard tolerance values of Table 1.
EXAMPLE 1 Toleranced size for a hole 90 F7
According to 4.3.2.2 IT7 = 35 µm
According to 4.3.2.3 Lower limit deviation EI = +36 µm
According to formula in Figure 8 Upper limit deviation ES = EI + IT = +36 + 35 = +71 µm
+0,071
From that follows: 90 F7 ≡ 90+0,036
EXAMPLE 2 Toleranced size for a shaft 90 f7
According to 4.3.2.2 IT7 = 35 µm
According to 4.3.2.3 Upper limit deviation es = −36 µm
According to formula in Figure 9 Lower limit deviation ei = es − IT = −36 − 35 = −71 µm
−0,036
From that follows: 90 f7 ≡−90 0,071
ISO 286-1:2010(E)
EXAMPLE 3 Toleranced size for a hole 29 P9
According to 4.3.2.2 IT7 = 52 µm
According to 4.3.2.3 Upper limit deviation ES = −22 µm
According to formula in Figure 8 Lower limit deviation EI = ES − IT = −22 − 52 = −74 µm
−0,022
From that follows: 28 P9 ≡−28 0,074
4.3.2.5 Establishment of limit deviations using ∆-values
For determining the fundamental deviations K, M and N for standard tolerance grades up to and including IT8
and P to ZC up to and including IT7, the values ∆ from the
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