# SIST ISO 286-1:1999

(Main)## ISO system of limits and fits -- Part 1: Bases of tolerances, deviations and fits

## ISO system of limits and fits -- Part 1: Bases of tolerances, deviations and fits

This part gives the bases of the ISO system of limits and fits together with the calculated values of the standard tolerances and fundamental deviations. It also gives terms and definitions together with associated symbols.

## Système ISO de tolérances et d'ajustements -- Partie 1: Base des tolérances, écarts et ajustements

La présente partie de l'ISO 286 fixe les bases d'un système ISO de tolérances et d'ajustements et donne les valeurs calculées des tolérances fondamentales et des écarts fondamentaux correspondants. Les valeurs font foi pour l'application du système (voir aussi chapitre A.1). La présente partie de l'ISO 286 donne la terminologie et les définitions à utiliser ainsi que les symboles correspondants.

Le système ISO de tolérances et d'ajustements fournit un système de tolérances et d'écarts applicables aux pièces lisses. Pour plus de simplicité et étant donné l'importance particulière des pièces cylindriques à section circulaire, seules celles-ci sont prévues explicitement. Mais il reste bien entendu que les tolérances et écarts donnés dans la présente Norme internationale s'appliquent également aux pièces lisses de section autre que circulaire. En particulier, les termes généraux «alésage» ou «arbre» désignent également l'espace, contenant ou contenu, compris entre deux faces (ou plans tangents) parallèles d'une pièce quelconque, tel que largeur de rainure, épaisseur de clavette, etc. Le système s'explique également à l'ajustement d'éléments cylindriques ou à l'ajustement de pièces présentant des éléments à faces parallèles, du type clavette et rainure de clavette, etc. NOTE -- Le système ne prévoit aucune règle d'ajustement pour des pi 216èces constituées d'éléments de forme géométrique autre que simple. Dans la présente partie de l'ISO 286, «forme géométrique simple» signifie une surface cylindrique ou deux plans parallèles.

## Sistem mejnih mer in ujemov ISO - 1. del: Osnove toleranc, odstopkov in ujemov

### General Information

### RELATIONS

### Standards Content (sample)

IS0

INTERNATIONAL STANDARD

286-l

First edition

1988-09-15

INTERNATIONAL ORGANIZATION FOR STANDARDIZATION

ORGANISATION INTERNATIONALE DE NORMALISATION

MEXJJYHAPOAHAR OPTAHM3A~Mfl f-t0 CTAHflAPTM3A~MM

IS0 system of limits and fits -

Part I :

Bases of tolerances, deviations and fits

Syst&me IS0 de tokkances et d’ajustements -

Partie 7 : Base des tokances, harts et ajustements

Reference number

IS0 286-l : 1988 (E)

---------------------- Page: 1 ----------------------

Foreword

IS0 (the International Organization for Standardization) is a worldwide federation of

national standards bodies (is0 member bodies). The work of preparing International

Standards is normally carried out through IS0 technical committees. Each memberbody interested in a subject for which a technical committee has been established has

the right to be represented on that committee. International organizations, govern-

mental and non-governmental, in liaison with ISO, also take part in the work.Draft International Standards adopted by the technical committees are circulated to

the member bodies for approval before their acceptance as International Standards by

the IS0 Council. They are approved in accordance with IS0 procedures requiring at

least 75 % approval by the member bodies voting.This part of IS0 286 has been prepared by ISO/TC 3, Limits and fits, and, together

with IS0 286-2, completes the revision of ISO/R 286, /SO system of limits and fits.

ISO/R 286 was first published in 1962 and subsequently confirmed in November 1964;

it was based on ISA Bulletin 25 first published in 1940.The major changes incorporated in this part of IS0 286 are as follows:

a) The presentation of the information has been modified so that IS0 286 can be

used directly in both the design office and the workshop. This has been achieved by

separating the material dealing with the bases of the system, and the calculatedvalues of standard tolerances and fundamental deviations, from the tables giving

specific limits of the most commonly used tolerances and deviations.

b) The new symbols js and JS replace the former symbols js and Js (i.e. s and S

are no longer placed as subscripts) to facilitate the use of the symbols on equipment

with limited character sets, e.g. computer graphics. The letters “s” and “S” stand

for “symmetrical deviation”.c) Standard tolerances and fundamental deviations have been included for basic

sizes from 500 to 3 150 mm as standard requirements (these were previously

included on an experimental basis only).

d) Two additional standard tolerance grades, IT17 and IT18, have been included.

e) Standard tolerance grades IT01 and IT0 have been deleted from the main body

of this part of IS0 286, although information on these grades is given in annex A

for users who may have a requirement for such grades.f) Inch values have been deleted.

aligned required

The principles, terminology and symbols

contemporary technology.

Users should note that all International Standards undergo revision from time to time

and that any reference made herein to any other International Standard implies its

latest edition, unless otherwise stated.0 International Organization for Standardization, 1988

Printed in Switzerland

---------------------- Page: 2 ----------------------

ISO286-1:1988 EI

Contents

Introduction. .......................................................

Scope .............................................................

Field of application ..................................................

References .........................................................

Terms and definitions ................................................

Symbols, designation and interpretation of tolerances, deviations

andfits.. ..........................................................

6 Graphical representation .............................................

7 Reference temperature ...............................................

8 Standard tolerances for basic sizes up to 3 150 mm. ...................... 10

Fundamental deviations for basic sizes up to 3 150 mm ...................

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

Annexes

............................... 17

A Bases of the IS0 system of limits and fits

....................................... 23

B Examples of the use of IS0 286-l

C Equivalentterms ....................................................

. . .

III

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INTERNATIONAL STANDARD IS02864 : 1988 (E)

IS0 system of limits and fits -

Part 1:

Bases of tolerances, deviations and fits

0 Introduction 2 Field of application

The need for limits and fits for machined workpieces was The IS0 system of limits and fits provides a system of

brought about mainly by the inherent inaccuracy of manufac- tolerances and deviations suitable for plain workpieces.’

turing methods, coupled with the fact that “exactness” of sizewas found to be unnecessary for most workpieces. In order For simplicity and also because of the importance of cylindrical

that function could be satisfied, it was found sufficient to workpieces of circular section, only these are referred to ex-

manufacture a given workpiece so that its size lay within two plicitly. It should be clearly understood, however, that the

tolerances and deviations given in this International Standardpermissible limits, i.e. a tolerance, this being the variation in

size acceptable in manufacture. equally apply to workpieces of other than circular section.

In particular, the general term “hole” or “shaft” can be takenSimilarly, where a specific fit condition is required between

mating workpieces, it is necessary to ascribe an allowance, as referring to the space contained by (or containing) the two

parallel faces (or tangent planes) of any workpiece, such as theeither positive or negative, to the basic size to achieve the re-

quired clearance or interference, i.e. a “deviation”. width of a slot or the thickness of a -key.

With developments in industry and international trade, it The system also provides for fits between mating cylindrical

became necessary to develop formal systems of limits and fits, features or fits between workpieces having features with

parallel faces, such as the fit between a key and keyway, etc.firstly at the industrial level, then at the national level and later

at the international level.

NOTE - It should be noted that the system is not intended to provide

fits for workpieces with features having other than simple geometric

This International Standard therefore gives the internationally

forms.

accepted system of limits and fits.

For the purposes of this part of IS0 286, a simple geometric form

consists of a cylindrical surface area or two parallel planes.

Annexes A and B give the basic formulae and rules necessary

for establishing the system, and examples in the use of the

standard are to be regarded as an integral part of the standard.

3 References

Annex C gives a list of equivalent terms used in IS0 286 and

NOTE - See also clause 10.

other International Standards on tolerances.

IS0 1, Standard reference temperature for industrial length

measurements.

1 Scope

IS0 286-2, IS0 system of limits and fits - Part 2: Tables of

standard tolerance grades and limit deviations for holes and

This part of IS0 286 gives the bases of the IS0 system of limits

shafts.

and fits together with the calculated values of the standard

tolerances and fundamental deviations. These values shall be

IS01 R 1938, IS0 system of limits and fits - Inspection of plain

taken as authoritative for the application of the system (see also

workpieces. 1 )

clause A. 1).

This part of IS0 286 also gives terms and definitions together IS0 8015, Technical drawings - Fundamental tolerancing

with associated symbols. principle.1) At present under revision.

---------------------- Page: 5 ----------------------

Is0 286-1 : 1988 E)

4.5 zero line: In a graphical representation of limits and fits,

4 Terms and definitions

the straight line, representing the basic size, to which the devi-

For the purposes of this International Standard, the following ations and tolerances are referred (see figure 7).

terms and definitions apply. It should be noted, however, thatn, the zero line is

According to conventio drawn horizontally,

some of the terms are defined in a more restricted sense than in

with positive deviations shown above and negative deviations

common usage.

below (see figure 2).

4.1 shaft: A term used, according to convention, to

describe an external feature of a workpiece, including features

which are not cylindrical (see also clause 2).

4.1.1 basic shaft: Shaft chosen as a basis for a shaft-basis

system of fits (see also 4.11.1).

Zero line (4.5)

For the purposes of the IS0 system of limits and fits, a shaft the

upper deviation of which is zero.

4.2 hole : A term used, according to convention, to describe

an internal feature of a workpiece, including features which are

not cylindrical (see also clause 2).

4.2.1 basic hole: Hole chosen as a basis for a hole-basis

system of fits (see also 4.11.2).

For the purposes of the IS0 system of limits and fits, a hole the

lower deviation of which is zero.

4.3 size : A number expressing, in a particular unit, the

Figure 1 - Basic size, and maxim urn and minimum

numerical value of a linear dimension.

limits of size

4.3.1 basic size; nominal size: The size from which the

4.6 deviation: The algebraic difference between a size

limits of size are derived by the application of the upper and

(actual size, limit of size, etc.) and the corresponding basic size.

lower deviations (see figure 1).

NOTE - Symbols for shaft deviations are lower case letters (es, ei) and

NOTE - The basic size or a number, symbols for hole deviations are upper case letters (Es, EI) (see

can be ae.g. 32; 15; 8,75; 0,5; etc. figure 2).

limit deviations : Upper deviation and lower deviation.

4.6.1

4.3.2 actual size: The size of a feature, obtained by

measurement.

4.6.1.1 upper deviation (ES, es) : The algebraic difference

between the maximum limit of size and the corresponding basic

size (see figure 2).

4.3.2.1 actual local size: Any individual distance at any

cross-section of a feature, i.e. any size measured between any

4.6.1.2 lower deviation (EL ei) : The algebraic difference

two opposite points.

between the minimum limit of size and the corresponding basic

size (see figure 2).

4.3.3 limits of size: The two extreme permissible sizes of a

feature, between which the actual size should lie, the limits of 4.6.2 fundamental deviation: For the purposes of the IS0

size being included. system of limits and fits, that deviation which defines theposition of the tolerance zone in relation to the zero line (see

figure 2).

4.3.3.1 maximum limit of size: The greatest permissible

size of a feature (see figure 1). NOTE - This may be either the upper or lower deviation, but, accord-

ing to convention, the fundamental deviation is the one nearest thezero line.

4.3.3.2 minimum limit of size : The smallest permissible size

of a feature (see figure 1).

4.7 size tolerance: The difference between the maximum

limit of size and the minimum limit of size, i.e. the difference

between the upper deviation and the lower deviation.

4.4 limit system: A system of standardized tolerances and

deviations.

NOTE - The tolerance is an absolute value without sign.

---------------------- Page: 6 ----------------------

IS0 286-l I 1988 E)

- Lower deviation (EI, ei 1 (4.6.1.2)

Clearance (4.8)

Tolerance zone (4.7.3)

tolerance (4.7)

- (ES, es)

P Zero line (4.5) (4.6.1.1) ,~

l - I w

2 F-

Figure 3 - Clearance

Figure 2 - Conventional representation of a

tolerance zone

4.8.1 minimum clearance: In a clearance fit, the positive

difference between the minimum limit of size of the hole and

the maximum limit of size of the shaft (see figure 4).

4.7.1 standard tolerance (IT) : For the purposes of the IS0

system of limits and fits, any tolerance belonging to this

4.8.2 maximum clearance: In a clearance or transition fit,

system.

the positive difference between the maximum limit of size of

the hole and the minimum limit of size of the shaft (see

NOTE - The letters of the symbol IT stand for “International

figures 4 and 5).

Tolerance” grade.

4.9 interference : The negative difference between the sizes

4.7.2 standard tolerance grades: For the purposes of the

of the hole and the shaft, before assembly, when the diameter

IS0 system of limits and fits, a group of tolerances (e.g. IJ7),

of the shaft is larger than the diameter of the hole (see

considered as corresponding to the same level of accuracy for

figure 6).

all basic sizes.

4.9.1 minimum interference: In an interference fit, the

4.7.3 tolerance zone : In a graphical representation of

negative difference, before assembly, between the maximum

tolerances, the zone, contained between two lines representing

limit of size of the hole and the minimum limit of size of the

the maximum and minimum limits of size, defined by the

shaft (see figure 7).

magnitude of the tolerance and its position relative to the zero

line (see figure 2).

4.7.4 tolerance class: The term used for a combination of

fundamental deviation and a tolerance grade, e.g. h9, D13, etc.

4.7.5 standard tolerance factor (i, I): For the purposes of .

the IS0 system of limits and fits, a factor which is a function of

the basic size, and which is used as a basis for the determi-

nation of the standard tolerances of the system.

NOTES

1 The standard tolerance factor i is applied to basic sizes less than or

equal to 500 mm.

The standard tolerance factor I is applied to basic sizes greater than

500 mm.

4.8 clearance: The positive difference between the sizes of

the hole and the shaft, before assembly, when the diameter of

the shaft is smaller than the diameter of the hole (see figure 3).

Figure 4 - Clearance fit

---------------------- Page: 7 ----------------------

IS0 286-1 : 1988 (E)

Maximum

Minimum

Maximum

clearance

interference ‘-1 I- interference

(4.8.2)

Maximum

Interference fit

Figure 7 -

interference 2

(4.9.2)

4.10.1 clearance fit: A fit that always provides a clearance

Figure 5 - Transition fit

between the hole and shaft when assembled, i.e. the minimum

size of the hole is either greater than or, in the extreme case,

equal to the maximum size of the shaft (see figure 8).

Interference

(4.9)

Hole

Hole

Shaft

Shaft

Figure 8 - Schematic representation of clearance fits

4.10.2 interference fit: A fit which everywhere provides an

interference between the hole and shaft when assembled, i.e.

the maximum size of the hole is either smaller than or, in the ex-

treme case, equal to the minimum size of the shaft (see

figure 9).

Figure 6 - Interference

Shaft

4.9.2 maximum interference: In an interference or tran-

Shaft

sition fit, the negative difference, before assembly, between

the minimum limit of size of the hole and the maximum limit of

size of the shaft (see figures 5 and 7).

4.10 fit: The relationship resulting from the difference,

Zero line .

before assembly, between the sizes of the two features (the t

Hole Hole

hole and the shaft) which are to be assembled.

NOTE - The two mating parts of a fit have a common basic size. Schematic representation of interference fits

Figure 9 ----------------------- Page: 8 ----------------------

IS0 286-l : 1988 (El

4.11.2 hole-basis. system of fits : A system of fits in which

4.103 transition fit: A fit which may provide either a

the required clearances or interferences are. obtained by

clearance or an interference between the hole and shaft when

associating shafts of various tolerance classes with holes of a

assembled, depending on the actual sizes of the hole and shaft,

single tolerance class.

i.e. the tolerance zones of the hole and the shaft overlap com-

pletely or in part (see figure IO).

For the purposes of the IS0 system of limits and fits, a system

of fits in which the minimum limit of size of the hole is identical

Shaft

. . .

to the basic size, i.e. the lower deviation is zero (see figure 12).

Hole

Zero line ,

Figure 10 - Schematic representation of transition fits

4.10.4 variation of a fit: The arithmetic sum of the

tolerances of the two features comprising the fit.

NOTE - The variation of a fit is an absolute value without sign.

4.11 fit system : A system of fits comprising shafts and

holes belonging to a limit system.

- Basic size (4.3.1)

4.11.1 shaft-basis system of fits: A system of fits in which

the required clearances or interferences are obtained by

NOTES

associating holes of various tolerance classes with shafts of a

single tolerance class.

1 The horizontal continuous lines represent the fundamental devi-

ations for holes or shafts.

For the purposes of the IS0 system of limits and fits, a system

of fits in which the maximum limit of size of the shaft is

2 The dashed lines represent the other limits and show the possibility

identical to the basic size, i.e. the upper deviation is zero (see

of different combinations between holes and shafts, related to their

figure I I).

grade of tolerance (e.g. H6/ h6, H6/js5, H6/p4).

Figure 12 - Hole-basis system of fits

4.12 maximum material limit (MML): The designation

applied to that of the two limits of size which corresponds to

the maximum material size for the feature, i.e.

the maximum (upper) limit of size for an external

feature (shaft),

Shaft “h”

the minimum (lower) limit of size for an internal feature

(hole).

NOTE - Previously called “GO limit”.

L Basic size (4.3.1)

4.13 least material limit (LMLI : The designation applied to

that of the two limits of size which corresponds to the minimum

NOTES material size for the feature, i.e.

1 The horizontal continuous lines represent the fundamental devi-

the minimum (lower) limit of size for an external feature

ations for holes or shafts.

(shaft),

2 The dashed lines represent the other limits and show the possibility

of different combinations between holes and shafts, related to their -

the maximum (upper) limit of size for an internal feature

grade of tolerance (e.g. G71h4, H6/h4, M5/h4).

(hole).

- Previously called “NOT GO limit”.

Figure 11 - Shaft-basis system of fits NOTE

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IS0 286-1 : 1988 (E)

Examples :

5 Symbols, designation and interpretation

of tolerances, deviations and fits

32H7

8OjsI5

10096

5.1 Symbols

-0 012

IO0 -0:034

5.1 .l Standard tolerance grades

ATTENTION - In order to distinguish between holes and

The standard tolerance grades are designated by the letters IT

shafts when transmitting information on equipment with

followed by a number, e.g. IJ7. When the tolerance grade is

limited character sets, such as telex, the designation shall be

associated with (a) letter(s) representing a fundamental

prefixed by the following letters:

deviation to form a tolerance class, the letters IT are omitted,

e.g. h7. -

H or h for holes;

- S or s for shafts.

NOTE - The IS0 system provides for a total of 20 standard tolerance

grades of which grades IT1 to IT18 are in general use and are given in

the main body of the standard. Grades IT0 and ITOl, which are not in Examples :

general use, are given in annex A for information purposes.

5OH5 becomes H5OH5 or h5Oh5

5Oh6 becomes S5OH6 or s5Oh6

5.1.2 Deviations

This method of designation shall not be on

drawings.

5.1.2.1 Position of tolerance zone

The position of the tolerance zone with respect to the zero line,

5.2.3 Fit

which is a function of the basic size, is designated by (an) upper

case letter(s) for holes (A . . . ZC) or (a) lower case letter(s) for

A fit requirement between mating features shall be designated

shafts (a . . . zc) (see figures I3 and 14).

NOTE - To avoid confusion, the following letters are not used :

a) the common basic size;

I, i; L, I; 0, 0; Q, q; W, w.

b) the tolerance class symbol for the hole;

c) the tolerance class symbol for the shaft.

5.1.2.2 Upper deviations

Examples :

The upper deviations are designated by the letters “ES” for

Ii7

52H7lg6 or 52 -

holes and the letters “es” for shafts.

ATTENTION - In order to distinguish between the hole and

5.1.2.3 Lower deviations

the shaft when transmitting information on equipment with

limited character sets, such as telex, the designation shall be

The lower deviations are designated by the letters “El” for

prefixed by the following letters:

holes and the letters “ei” for shafts.

- H or h for holes;

5.2 Designation

- S or s for shafts;

and the basic size repeated.

5.2.1 Tolerance class

Examples :

A tolerance class shall be designated by the letter(s) represent-

ing the fundamental deviation followed by the number

52H7/g6 becomes H52H7/S52G6 or h52h7/s52g6

representing the standard tolerance grade.

This method of designation shall not be used on

Examples :

drawings.

H7 (holes)

h7 (shafts)

5.3 Interpretation of a toleranced size

5.3.1 Tolerance indication in accordance with IS0 8015

5.2.2 Toleranced size

The tolerances for workpieces manufactured to drawings

A toleranced size shall be designated by the basic size followed

marked with the notation, Tolerancing IS0 8015, shall be

by the designation of the required tolerance class, or the ex-

plicit deviations. interpreted as indicated in 5.3. I. I and 5.3.1.2.

---------------------- Page: 10 ----------------------

Is0 286-I : 1988 (El

a) Holes (internal features)

b) Shafts (external features)

NOTES

I According to convention, the fundamental deviation is the one defining the nearest limit to the zero line.

2 For details concerning fundamental deviations for J/j, K/k, M/m and N/n, see figure 14.

Figure 13 - Schematic representation of the positions of fundamental deviations---------------------- Page: 11 ----------------------

60286-1:1988 E)

I-- l-

. .

. .

CL) LLJ

0 0

z z

---------------------- Page: 12 ----------------------

IS0 286-k 1988 a(E)

6 Graphical representation

53.1 .I Linear size tolerances

The major terms and definitions given in clause 4 are illustrated

A linear size tolerance controls only the actual local sizes (two-

in figure 15.

point measurements) of a feature, but not its form deviations

(for example circularity and straightness deviations of a cylin-

In practice, a schematic diagram such as that shown in

drical feature or flatness deviations of parallel surfaces). There

figure 16 is used for simplicity. In this diagram, the axis of the

is no control of the geometrical interrelationship of individual

workpiece, which is not shown in the figure, according to con-

features by the size tolerances. (For further information, see

vention always lies below the diagram.

ISO/R 1938 and IS0 8015.)

two deviations of the hole are

In the example illustrated, the

5.3.1.2 Envelope requirement

positive and those of the shaft are negative.

Single features, whether a cylinder, or established by two

parallel planes, having the function of a fit between mating

parts, are indicated on the drawing by the symbol @ in ad-

Upper deviation (4.6.1.1) -

dition to the dimension and tolerance. This indicates a mutual

Lower deviation (4.6.1.2)

dependence of size and form which requires that the envelope

of perfect form for the feature at maximum material size shall

not be violated. (For further information, see ISO/R 1938 and Hole (4.2)

r r

IS0 8015.)

NOTE - Some national standards (which should be referred to on the

drawing) specify that the envelope requirement for single features is

the norm and therefore this is not indicated separately on the drawing.

53.2 Tolerance indication not in accordance with

IS0 6015

The tolerances for workpieces manufactured to drawings

which do not have the notation, Tolerancing IS0 6015, shall

be interpreted in the following ways within the stipulated

length :

a) For holes

The diameter of the largest perfect imaginary cylinder,

which can be inscribed within the hole so that it just con-

tacts the highest points of the surface, should not be smaller

than the maximum material limit of size. The maximum

diameter at any position in the hole shall not exceed the

Minimum limit of size (4.3.3.2) -

least material limit of size.

Maximum limit of size (4.3.3.1)

b) For shafts

Basic size (4.3.1)

The diameter of the smallest perfect imaginary cylinder,

which can be circumscribed about the shaft so that it just

Figure 15 - Graphical representation

contacts the highest points of the surface, should not be

larger than the maximum material limit of size. The mini-

mum diameter at any position on the shaft shall be not less

than the least material limit of size.

Hole

The interpretations given in a) and b) mean that if a workpiece

is everywhere at its maximum material limit, that workpiece

should be perfectly round and straight, i.e. a perfect cylinder.

Unless otherwise specified, and subject to the above require-

ments, departures from a perfect cylinder may reach the full 2

value of the diameter tolerance specified. For further informa-

Shaft

tion, see ISO/R 1938.

NOTE -

In special cases, the maximum form deviations permitted by

the interpretations given in a) and b) may be too large to allow satisfac-

tory functioning of the assembled parts: in such cases, separate

tolerances should be given for the form, e.g. separate tolerances on

Figure 16 - Simplified schematic diagram

circularity and/or straightness (see IS0 1101).

---------------------- Page: 13 ----------------------

IS0 286-l : 1988 (El

7 Reference temperature 9.2 Fundamental deviations for holes

[except deviation JS (see 9.311

The temperature at which the dimensions of the IS0 system of

limits and fits are specified is 20 OC (see IS0 I). The fundamental deviations for holes and their respective sign

( + or - ) are shown in figure 18. Values for the fundamentaldeviations are given in table 3.

The upper deviation (ES) and lower deviation (H) are

8 Standard tolerances for basic sizes up to

established from the fundamental deviation and the standard

315Omm

tolerance grade (IT) as shown in figure 18.

8.1 Basis of the system

Deviations A to H Deviations K to ZC

The bases for calculating the standard tolerances are given in

(not valid for tolerance grades

annex A.

less than or equal to IT8

of deviation K and tolerance

class M8)

8.2 Values of standard tolerance grades (IT)

Values of standard tolerance grades IT1 to IT18 inclusive are

Zero line

given in table 1. These values are to be taken as authoritative

for the application of the system.

NOTE - Values for standard tolerance grades IT0 and IT01 are given in

annex A.

ES = negative ( - 1 funda-

EI = positive (+ 1 funda-

9 Fundamental deviations for basic sizes up

mental deviation mental deviation

to315Omm

ES = EI + IT EI = ES - IT

9.1 Fundamental deviations for shafts

[except deviation js (see 9.3)]

Figure 18 - Deviations for holes

The fundamental deviations for shafts and their respective sign

( + or - 1 are shown in figure 17. Values for the fundamental

9.3 Fundamental deviations js and JS

deviations are given in table 2.

(see figure 19)

The upper deviation (es) and lower deviation (ei) are estab-

The information given in 9.1 and 9.2 does not apply to fun-

lished from the fundamental deviation and the standard

damental deviations js and JS, which are a symmetrical

tolerance grade (IT) as shown in figure 17.

distribution of the standard tolerance grade about the zero line,

i.e. for js:

Deviations a to h Deviations k to zc IT

es = ei = -

and for JS:

ES = EI.= -

Zero line

es ES

ei = positive ( + ) funda-

es = negative ( - 1 funda-

Shaft

I Hole

mental deviation

mental deviation

ei = es - IT es = ei + IT

Figure 17 - Deviations for shafts

Deviations js and JS

Figure 19 -

---------------------- Page: 14 ----------------------

IS0 286-1 : 1988 (EI

9.4 Fundamental deviations j and J

The information given in 9.1 to 9.3 does not apply to fundamental deviations j and J, which are, for the most part, asymmetrical distributions

of the standard tolerance grade about the zero line (see IS0 286-2, tables 8 and 24).

Numerical values of standard tolerance grades IT for basic sizes up to 3 150 mm ‘)

Table 1 -Standard tolerance grades

Basic size

IT7 IT8 1 IT8 1 IT10 ] IT11 1 IT12 1 IT13 1 lTl43)1

IT153) 1 IT1631 ITl73)I IT1831

up to

Tolerances

Above and in-

cluding mm

IJm

- 33) 0,8 I,2 2 3 4 6 10 14 25 40

60 0,l 0,14 0,25 0,4 0,6 1 114

3 6 1

1,5 2,5 4 5 8 12 18 30 48 75 0,12 0,18 0,3 0,48 0,75 1,2

I,8

6 10 1 I,5 2,5 4

6 9 15 22 36 58 90 0,15 0,22 0,36 0,58 0;9 I,5

2,2

10 18 I,2 2 3 5 8 11 18 27 43

70 110 0,18 0,27 0,43 0,7 1,1' I,8 2,7

18 30

I,5 2,5 4 6 9 13 21 33 52 84 130 0,21

0,33 0,52 0,84 I,3 2,l 3,3

30 50 I,5 2,5 4 7 11 16 25

39 62 100 160 0,25 0,39 0,62 1 1,6 2,5 3,9

50 80 2,, 3 5 8 13 19 30 46 74

120 190 0,3 0,46 0,74 1,2 I,9 3 4,6

80 120

2,5 4 6 10 15 22 35 54 87 140 220 0,35

0,54 0,87 I,4 2,2 3,5 5,4-

120 180 3,5 5 8 12 18 25

40 63 100 160 250 0,4 0,63 1 I,6 2,5 4 613

180 250 4,5 7 10 14

**...**

SLOVENSKI STANDARD

SIST ISO 286-1:1999

01-marec-1999

Sistem mejnih mer in ujemov ISO - 1. del: Osnove toleranc, odstopkov in ujemov

ISO system of limits and fits -- Part 1: Bases of tolerances, deviations and fits

Système ISO de tolérances et d'ajustements -- Partie 1: Base des tolérances, écarts et

ajustementsTa slovenski standard je istoveten z: ISO 286-1:1988

ICS:

17.040.10 Tolerance in ujemi Limits and fits

SIST ISO 286-1:1999 en

2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

---------------------- Page: 1 ----------------------SIST ISO 286-1:1999

---------------------- Page: 2 ----------------------

SIST ISO 286-1:1999

IS0

INTERNATIONAL STANDARD

286-l

First edition

1988-09-15

INTERNATIONAL ORGANIZATION FOR STANDARDIZATION

ORGANISATION INTERNATIONALE DE NORMALISATION

MEXJJYHAPOAHAR OPTAHM3A~Mfl f-t0 CTAHflAPTM3A~MM

IS0 system of limits and fits -

Part I :

Bases of tolerances, deviations and fits

Syst&me IS0 de tokkances et d’ajustements -

Partie 7 : Base des tokances, harts et ajustements

Reference number

IS0 286-l : 1988 (E)

---------------------- Page: 3 ----------------------

SIST ISO 286-1:1999

Foreword

IS0 (the International Organization for Standardization) is a worldwide federation of

national standards bodies (is0 member bodies). The work of preparing International

Standards is normally carried out through IS0 technical committees. Each memberbody interested in a subject for which a technical committee has been established has

the right to be represented on that committee. International organizations, govern-

mental and non-governmental, in liaison with ISO, also take part in the work.Draft International Standards adopted by the technical committees are circulated to

the member bodies for approval before their acceptance as International Standards by

the IS0 Council. They are approved in accordance with IS0 procedures requiring at

least 75 % approval by the member bodies voting.This part of IS0 286 has been prepared by ISO/TC 3, Limits and fits, and, together

with IS0 286-2, completes the revision of ISO/R 286, /SO system of limits and fits.

ISO/R 286 was first published in 1962 and subsequently confirmed in November 1964;

it was based on ISA Bulletin 25 first published in 1940.The major changes incorporated in this part of IS0 286 are as follows:

a) The presentation of the information has been modified so that IS0 286 can be

used directly in both the design office and the workshop. This has been achieved by

separating the material dealing with the bases of the system, and the calculatedvalues of standard tolerances and fundamental deviations, from the tables giving

specific limits of the most commonly used tolerances and deviations.

b) The new symbols js and JS replace the former symbols js and Js (i.e. s and S

are no longer placed as subscripts) to facilitate the use of the symbols on equipment

with limited character sets, e.g. computer graphics. The letters “s” and “S” stand

for “symmetrical deviation”.c) Standard tolerances and fundamental deviations have been included for basic

sizes from 500 to 3 150 mm as standard requirements (these were previously

included on an experimental basis only).

d) Two additional standard tolerance grades, IT17 and IT18, have been included.

e) Standard tolerance grades IT01 and IT0 have been deleted from the main body

of this part of IS0 286, although information on these grades is given in annex A

for users who may have a requirement for such grades.f) Inch values have been deleted.

aligned required

The principles, terminology and symbols

contemporary technology.

Users should note that all International Standards undergo revision from time to time

and that any reference made herein to any other International Standard implies its

latest edition, unless otherwise stated.0 International Organization for Standardization, 1988

Printed in Switzerland

---------------------- Page: 4 ----------------------

SIST ISO 286-1:1999

ISO286-1:1988 EI

Contents

Introduction. .......................................................

Scope .............................................................

Field of application ..................................................

References .........................................................

Terms and definitions ................................................

Symbols, designation and interpretation of tolerances, deviations

andfits.. ..........................................................

6 Graphical representation .............................................

7 Reference temperature ...............................................

8 Standard tolerances for basic sizes up to 3 150 mm. ...................... 10

Fundamental deviations for basic sizes up to 3 150 mm ...................

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

Annexes

............................... 17

A Bases of the IS0 system of limits and fits

....................................... 23

B Examples of the use of IS0 286-l

C Equivalentterms ....................................................

. . .

III

---------------------- Page: 5 ----------------------

SIST ISO 286-1:1999

This page intentionally left blank

---------------------- Page: 6 ----------------------

SIST ISO 286-1:1999

INTERNATIONAL STANDARD IS02864 : 1988 (E)

IS0 system of limits and fits -

Part 1:

Bases of tolerances, deviations and fits

0 Introduction 2 Field of application

The need for limits and fits for machined workpieces was The IS0 system of limits and fits provides a system of

brought about mainly by the inherent inaccuracy of manufac- tolerances and deviations suitable for plain workpieces.’

turing methods, coupled with the fact that “exactness” of sizewas found to be unnecessary for most workpieces. In order For simplicity and also because of the importance of cylindrical

that function could be satisfied, it was found sufficient to workpieces of circular section, only these are referred to ex-

manufacture a given workpiece so that its size lay within two plicitly. It should be clearly understood, however, that the

tolerances and deviations given in this International Standardpermissible limits, i.e. a tolerance, this being the variation in

size acceptable in manufacture. equally apply to workpieces of other than circular section.

In particular, the general term “hole” or “shaft” can be takenSimilarly, where a specific fit condition is required between

mating workpieces, it is necessary to ascribe an allowance, as referring to the space contained by (or containing) the two

parallel faces (or tangent planes) of any workpiece, such as theeither positive or negative, to the basic size to achieve the re-

quired clearance or interference, i.e. a “deviation”. width of a slot or the thickness of a -key.

With developments in industry and international trade, it The system also provides for fits between mating cylindrical

became necessary to develop formal systems of limits and fits, features or fits between workpieces having features with

parallel faces, such as the fit between a key and keyway, etc.firstly at the industrial level, then at the national level and later

at the international level.

NOTE - It should be noted that the system is not intended to provide

fits for workpieces with features having other than simple geometric

This International Standard therefore gives the internationally

forms.

accepted system of limits and fits.

For the purposes of this part of IS0 286, a simple geometric form

consists of a cylindrical surface area or two parallel planes.

Annexes A and B give the basic formulae and rules necessary

for establishing the system, and examples in the use of the

standard are to be regarded as an integral part of the standard.

3 References

Annex C gives a list of equivalent terms used in IS0 286 and

NOTE - See also clause 10.

other International Standards on tolerances.

IS0 1, Standard reference temperature for industrial length

measurements.

1 Scope

IS0 286-2, IS0 system of limits and fits - Part 2: Tables of

standard tolerance grades and limit deviations for holes and

This part of IS0 286 gives the bases of the IS0 system of limits

shafts.

and fits together with the calculated values of the standard

tolerances and fundamental deviations. These values shall be

IS01 R 1938, IS0 system of limits and fits - Inspection of plain

taken as authoritative for the application of the system (see also

workpieces. 1 )

clause A. 1).

This part of IS0 286 also gives terms and definitions together IS0 8015, Technical drawings - Fundamental tolerancing

with associated symbols. principle.1) At present under revision.

---------------------- Page: 7 ----------------------

SIST ISO 286-1:1999

Is0 286-1 : 1988 E)

4.5 zero line: In a graphical representation of limits and fits,

4 Terms and definitions

the straight line, representing the basic size, to which the devi-

For the purposes of this International Standard, the following ations and tolerances are referred (see figure 7).

terms and definitions apply. It should be noted, however, thatn, the zero line is

According to conventio drawn horizontally,

some of the terms are defined in a more restricted sense than in

with positive deviations shown above and negative deviations

common usage.

below (see figure 2).

4.1 shaft: A term used, according to convention, to

describe an external feature of a workpiece, including features

which are not cylindrical (see also clause 2).

4.1.1 basic shaft: Shaft chosen as a basis for a shaft-basis

system of fits (see also 4.11.1).

Zero line (4.5)

For the purposes of the IS0 system of limits and fits, a shaft the

upper deviation of which is zero.

4.2 hole : A term used, according to convention, to describe

an internal feature of a workpiece, including features which are

not cylindrical (see also clause 2).

4.2.1 basic hole: Hole chosen as a basis for a hole-basis

system of fits (see also 4.11.2).

For the purposes of the IS0 system of limits and fits, a hole the

lower deviation of which is zero.

4.3 size : A number expressing, in a particular unit, the

Figure 1 - Basic size, and maxim urn and minimum

numerical value of a linear dimension.

limits of size

4.3.1 basic size; nominal size: The size from which the

4.6 deviation: The algebraic difference between a size

limits of size are derived by the application of the upper and

(actual size, limit of size, etc.) and the corresponding basic size.

lower deviations (see figure 1).

NOTE - Symbols for shaft deviations are lower case letters (es, ei) and

NOTE - The basic size or a number, symbols for hole deviations are upper case letters (Es, EI) (see

can be ae.g. 32; 15; 8,75; 0,5; etc. figure 2).

limit deviations : Upper deviation and lower deviation.

4.6.1

4.3.2 actual size: The size of a feature, obtained by

measurement.

4.6.1.1 upper deviation (ES, es) : The algebraic difference

between the maximum limit of size and the corresponding basic

size (see figure 2).

4.3.2.1 actual local size: Any individual distance at any

cross-section of a feature, i.e. any size measured between any

4.6.1.2 lower deviation (EL ei) : The algebraic difference

two opposite points.

between the minimum limit of size and the corresponding basic

size (see figure 2).

4.3.3 limits of size: The two extreme permissible sizes of a

feature, between which the actual size should lie, the limits of 4.6.2 fundamental deviation: For the purposes of the IS0

size being included. system of limits and fits, that deviation which defines theposition of the tolerance zone in relation to the zero line (see

figure 2).

4.3.3.1 maximum limit of size: The greatest permissible

size of a feature (see figure 1). NOTE - This may be either the upper or lower deviation, but, accord-

ing to convention, the fundamental deviation is the one nearest thezero line.

4.3.3.2 minimum limit of size : The smallest permissible size

of a feature (see figure 1).

4.7 size tolerance: The difference between the maximum

limit of size and the minimum limit of size, i.e. the difference

between the upper deviation and the lower deviation.

4.4 limit system: A system of standardized tolerances and

deviations.

NOTE - The tolerance is an absolute value without sign.

---------------------- Page: 8 ----------------------

SIST ISO 286-1:1999

IS0 286-l I 1988 E)

- Lower deviation (EI, ei 1 (4.6.1.2)

Clearance (4.8)

Tolerance zone (4.7.3)

tolerance (4.7)

- (ES, es)

P Zero line (4.5) (4.6.1.1) ,~

l - I w

2 F-

Figure 3 - Clearance

Figure 2 - Conventional representation of a

tolerance zone

4.8.1 minimum clearance: In a clearance fit, the positive

difference between the minimum limit of size of the hole and

the maximum limit of size of the shaft (see figure 4).

4.7.1 standard tolerance (IT) : For the purposes of the IS0

system of limits and fits, any tolerance belonging to this

4.8.2 maximum clearance: In a clearance or transition fit,

system.

the positive difference between the maximum limit of size of

the hole and the minimum limit of size of the shaft (see

NOTE - The letters of the symbol IT stand for “International

figures 4 and 5).

Tolerance” grade.

4.9 interference : The negative difference between the sizes

4.7.2 standard tolerance grades: For the purposes of the

of the hole and the shaft, before assembly, when the diameter

IS0 system of limits and fits, a group of tolerances (e.g. IJ7),

of the shaft is larger than the diameter of the hole (see

considered as corresponding to the same level of accuracy for

figure 6).

all basic sizes.

4.9.1 minimum interference: In an interference fit, the

4.7.3 tolerance zone : In a graphical representation of

negative difference, before assembly, between the maximum

tolerances, the zone, contained between two lines representing

limit of size of the hole and the minimum limit of size of the

the maximum and minimum limits of size, defined by the

shaft (see figure 7).

magnitude of the tolerance and its position relative to the zero

line (see figure 2).

4.7.4 tolerance class: The term used for a combination of

fundamental deviation and a tolerance grade, e.g. h9, D13, etc.

4.7.5 standard tolerance factor (i, I): For the purposes of .

the IS0 system of limits and fits, a factor which is a function of

the basic size, and which is used as a basis for the determi-

nation of the standard tolerances of the system.

NOTES

1 The standard tolerance factor i is applied to basic sizes less than or

equal to 500 mm.

The standard tolerance factor I is applied to basic sizes greater than

500 mm.

4.8 clearance: The positive difference between the sizes of

the hole and the shaft, before assembly, when the diameter of

the shaft is smaller than the diameter of the hole (see figure 3).

Figure 4 - Clearance fit

---------------------- Page: 9 ----------------------

SIST ISO 286-1:1999

IS0 286-1 : 1988 (E)

Maximum

Minimum

Maximum

clearance

interference ‘-1 I- interference

(4.8.2)

Maximum

Interference fit

Figure 7 -

interference 2

(4.9.2)

4.10.1 clearance fit: A fit that always provides a clearance

Figure 5 - Transition fit

between the hole and shaft when assembled, i.e. the minimum

size of the hole is either greater than or, in the extreme case,

equal to the maximum size of the shaft (see figure 8).

Interference

(4.9)

Hole

Hole

Shaft

Shaft

Figure 8 - Schematic representation of clearance fits

4.10.2 interference fit: A fit which everywhere provides an

interference between the hole and shaft when assembled, i.e.

the maximum size of the hole is either smaller than or, in the ex-

treme case, equal to the minimum size of the shaft (see

figure 9).

Figure 6 - Interference

Shaft

4.9.2 maximum interference: In an interference or tran-

Shaft

sition fit, the negative difference, before assembly, between

the minimum limit of size of the hole and the maximum limit of

size of the shaft (see figures 5 and 7).

4.10 fit: The relationship resulting from the difference,

Zero line .

before assembly, between the sizes of the two features (the t

Hole Hole

hole and the shaft) which are to be assembled.

NOTE - The two mating parts of a fit have a common basic size. Schematic representation of interference fits

Figure 9 ----------------------- Page: 10 ----------------------

SIST ISO 286-1:1999

IS0 286-l : 1988 (El

4.11.2 hole-basis. system of fits : A system of fits in which

4.103 transition fit: A fit which may provide either a

the required clearances or interferences are. obtained by

clearance or an interference between the hole and shaft when

associating shafts of various tolerance classes with holes of a

assembled, depending on the actual sizes of the hole and shaft,

single tolerance class.

i.e. the tolerance zones of the hole and the shaft overlap com-

pletely or in part (see figure IO).

For the purposes of the IS0 system of limits and fits, a system

of fits in which the minimum limit of size of the hole is identical

Shaft

. . .

to the basic size, i.e. the lower deviation is zero (see figure 12).

Hole

Zero line ,

Figure 10 - Schematic representation of transition fits

4.10.4 variation of a fit: The arithmetic sum of the

tolerances of the two features comprising the fit.

NOTE - The variation of a fit is an absolute value without sign.

4.11 fit system : A system of fits comprising shafts and

holes belonging to a limit system.

- Basic size (4.3.1)

4.11.1 shaft-basis system of fits: A system of fits in which

the required clearances or interferences are obtained by

NOTES

associating holes of various tolerance classes with shafts of a

single tolerance class.

1 The horizontal continuous lines represent the fundamental devi-

ations for holes or shafts.

For the purposes of the IS0 system of limits and fits, a system

of fits in which the maximum limit of size of the shaft is

2 The dashed lines represent the other limits and show the possibility

identical to the basic size, i.e. the upper deviation is zero (see

of different combinations between holes and shafts, related to their

figure I I).

grade of tolerance (e.g. H6/ h6, H6/js5, H6/p4).

Figure 12 - Hole-basis system of fits

4.12 maximum material limit (MML): The designation

applied to that of the two limits of size which corresponds to

the maximum material size for the feature, i.e.

the maximum (upper) limit of size for an external

feature (shaft),

Shaft “h”

the minimum (lower) limit of size for an internal feature

(hole).

NOTE - Previously called “GO limit”.

L Basic size (4.3.1)

4.13 least material limit (LMLI : The designation applied to

that of the two limits of size which corresponds to the minimum

NOTES material size for the feature, i.e.

1 The horizontal continuous lines represent the fundamental devi-

the minimum (lower) limit of size for an external feature

ations for holes or shafts.

(shaft),

2 The dashed lines represent the other limits and show the possibility

of different combinations between holes and shafts, related to their -

the maximum (upper) limit of size for an internal feature

grade of tolerance (e.g. G71h4, H6/h4, M5/h4).

(hole).

- Previously called “NOT GO limit”.

Figure 11 - Shaft-basis system of fits NOTE

---------------------- Page: 11 ----------------------

SIST ISO 286-1:1999

IS0 286-1 : 1988 (E)

Examples :

5 Symbols, designation and interpretation

of tolerances, deviations and fits

32H7

8OjsI5

10096

5.1 Symbols

-0 012

IO0 -0:034

5.1 .l Standard tolerance grades

ATTENTION - In order to distinguish between holes and

The standard tolerance grades are designated by the letters IT

shafts when transmitting information on equipment with

followed by a number, e.g. IJ7. When the tolerance grade is

limited character sets, such as telex, the designation shall be

associated with (a) letter(s) representing a fundamental

prefixed by the following letters:

deviation to form a tolerance class, the letters IT are omitted,

e.g. h7. -

H or h for holes;

- S or s for shafts.

NOTE - The IS0 system provides for a total of 20 standard tolerance

grades of which grades IT1 to IT18 are in general use and are given in

the main body of the standard. Grades IT0 and ITOl, which are not in Examples :

general use, are given in annex A for information purposes.

5OH5 becomes H5OH5 or h5Oh5

5Oh6 becomes S5OH6 or s5Oh6

5.1.2 Deviations

This method of designation shall not be on

drawings.

5.1.2.1 Position of tolerance zone

The position of the tolerance zone with respect to the zero line,

5.2.3 Fit

which is a function of the basic size, is designated by (an) upper

case letter(s) for holes (A . . . ZC) or (a) lower case letter(s) for

A fit requirement between mating features shall be designated

shafts (a . . . zc) (see figures I3 and 14).

NOTE - To avoid confusion, the following letters are not used :

a) the common basic size;

I, i; L, I; 0, 0; Q, q; W, w.

b) the tolerance class symbol for the hole;

c) the tolerance class symbol for the shaft.

5.1.2.2 Upper deviations

Examples :

The upper deviations are designated by the letters “ES” for

Ii7

52H7lg6 or 52 -

holes and the letters “es” for shafts.

ATTENTION - In order to distinguish between the hole and

5.1.2.3 Lower deviations

the shaft when transmitting information on equipment with

limited character sets, such as telex, the designation shall be

The lower deviations are designated by the letters “El” for

prefixed by the following letters:

holes and the letters “ei” for shafts.

- H or h for holes;

5.2 Designation

- S or s for shafts;

and the basic size repeated.

5.2.1 Tolerance class

Examples :

A tolerance class shall be designated by the letter(s) represent-

ing the fundamental deviation followed by the number

52H7/g6 becomes H52H7/S52G6 or h52h7/s52g6

representing the standard tolerance grade.

This method of designation shall not be used on

Examples :

drawings.

H7 (holes)

h7 (shafts)

5.3 Interpretation of a toleranced size

5.3.1 Tolerance indication in accordance with IS0 8015

5.2.2 Toleranced size

The tolerances for workpieces manufactured to drawings

A toleranced size shall be designated by the basic size followed

marked with the notation, Tolerancing IS0 8015, shall be

by the designation of the required tolerance class, or the ex-

plicit deviations. interpreted as indicated in 5.3. I. I and 5.3.1.2.

---------------------- Page: 12 ----------------------

SIST ISO 286-1:1999

Is0 286-I : 1988 (El

a) Holes (internal features)

b) Shafts (external features)

NOTES

I According to convention, the fundamental deviation is the one defining the nearest limit to the zero line.

2 For details concerning fundamental deviations for J/j, K/k, M/m and N/n, see figure 14.

Figure 13 - Schematic representation of the positions of fundamental deviations---------------------- Page: 13 ----------------------

SIST ISO 286-1:1999

60286-1:1988 E)

I-- l-

. .

. .

CL) LLJ

0 0

z z

---------------------- Page: 14 ----------------------

SIST ISO 286-1:1999

IS0 286-k 1988 a(E)

6 Graphical representation

53.1 .I Linear size tolerances

The major terms and definitions given in clause 4 are illustrated

A linear size tolerance controls only the actual local sizes (two-

in figure 15.

point measurements) of a feature, but not its form deviations

(for example circularity and straightness deviations of a cylin-

In practice, a schematic diagram such as that shown in

drical feature or flatness deviations of parallel surfaces). There

figure 16 is used for simplicity. In this diagram, the axis of the

is no control of the geometrical interrelationship of individual

workpiece, which is not shown in the figure, according to con-

features by the size tolerances. (For further information, see

vention always lies below the diagram.

ISO/R 1938 and IS0 8015.)

two deviations of the hole are

In the example illustrated, the

5.3.1.2 Envelope requirement

positive and those of the shaft are negative.

Single features, whether a cylinder, or established by two

parallel planes, having the function of a fit between mating

parts, are indicated on the drawing by the symbol @ in ad-

Upper deviation (4.6.1.1) -

dition to the dimension and tolerance. This indicates a mutual

Lower deviation (4.6.1.2)

dependence of size and form which requires that the envelope

of perfect form for the feature at maximum material size shall

not be violated. (For further information, see ISO/R 1938 and Hole (4.2)

r r

IS0 8015.)

NOTE - Some national standards (which should be referred to on the

drawing) specify that the envelope requirement for single features is

the norm and therefore this is not indicated separately on the drawing.

53.2 Tolerance indication not in accordance with

IS0 6015

The tolerances for workpieces manufactured to drawings

which do not have the notation, Tolerancing IS0 6015, shall

be interpreted in the following ways within the stipulated

length :

a) For holes

The diameter of the largest perfect imaginary cylinder,

which can be inscribed within the hole so that it just con-

tacts the highest points of the surface, should not be smaller

than the maximum material limit of size. The maximum

diameter at any position in the hole shall not exceed the

Minimum limit of size (4.3.3.2) -

least material limit of size.

Maximum limit of size (4.3.3.1)

b) For shafts

Basic size (4.3.1)

The diameter of the smallest perfect imaginary cylinder,

which can be circumscribed about the shaft so that it just

Figure 15 - Graphical representation

contacts the highest points of the surface, should not be

larger than the maximum material limit of size. The mini-

mum diameter at any position on the shaft shall be not less

than the least material limit of size.

Hole

The interpretations given in a) and b) mean that if a workpiece

is everywhere at its maximum material limit, that workpiece

should be perfectly round and straight, i.e. a perfect cylinder.

Unless otherwise specified, and subject to the above require-

ments, departures from a perfect cylinder may reach the full 2

value of the diameter tolerance specified. For further informa-

Shaft

tion, see ISO/R 1938.

NOTE -

In special cases, the maximum form deviations permitted by

the interpretations given in a) and b) may be too large to allow satisfac-

tory functioning of the assembled parts: in such cases, separate

tolerances should be given for the form, e.g. separate tolerances on

Figure 16 - Simplified schematic diagram

circularity and/or straightness (see IS0 1101).

---------------------- Page: 15 ----------------------

SIST ISO 286-1:1999

IS0 286-l : 1988 (El

7 Reference temperature 9.2 Fundamental deviations for holes

[except deviation JS (see 9.311

The temperature at which the dimensions of the IS0 system of

limits and fits are specified is 20 OC (see IS0 I). The fundamental deviations for holes and their respective sign

( + or - ) are shown in figure 18. Values for the fundamentaldeviations are given in table 3.

The upper deviation (ES) and lower deviation (H) are

8 Standard tolerances for basic sizes up to

established from the fundamental deviation and the standard

315Omm

tolerance grade (IT) as shown in figure 18.

8.1 Basis of the system

Deviations A to H Deviations K to ZC

The bases for calculating the standard tolerances are given in

(not valid for tolerance grades

annex A.

less than or equal to IT8

of deviation K and tolerance

class M8)

8.2 Values of standard tolerance grades (IT)

Values of standard tolerance grades IT1 to IT18 inclusive are

Zero line

given in table 1. These values are to be taken as authoritative

for the application of the system.

NOTE - Values for standard tolerance grades IT0 and IT01 are given in

annex A.

ES = negative ( - 1 funda-

EI = positive (+ 1 funda-

9 Fundamental deviations for basic sizes up

mental deviation mental deviation

to315Omm

ES = EI + IT EI = ES - IT

9.1 Fundamental deviations for shafts

[except deviation js (see 9.3)]

Figure 18 - Deviations for holes

The fundamental deviations for shafts and their respective sign

( + or - 1 are shown in figure 17. Values for the fundamental

9.3 Fundamental deviations js and JS

deviations are given in table 2.

(see figure 19)

The upper deviation (es) and lower deviation (ei) are estab-

The information given in 9.1 and 9.2 does not apply to fun-

lished from the fundamental deviation and the standard

damental deviations js and JS, which are a symmetrical

tolerance grade (IT) as shown in figure 17.

distribution of the standard tolerance grade about the zero line,

i.e. for js:

Deviations a to h Deviations k to zc IT

es = ei = -

and for JS:

ES = EI.= -

Zero line

es ES

ei = positive ( + ) funda-

es = negative ( - 1 funda-

Shaft

I Hole

mental deviation

mental deviation

ei = es - IT es = ei + IT

Figure 17 - Deviations for shafts

Deviations js and JS

Figure 19 -

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SIST ISO 286-1:1999

IS0 286-1 : 1988 (EI

9.4 Fundamental deviations j and J

The information given in 9.1 to 9.3 does not apply to fundamental deviations j and J, which are, for the most part, asymmetrical distributions

of the**...**

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