|
U DC 621.753.11 2
IS0
INTERNATIONAL ORGANIZATION FOR STANDARDIZATION
IS0 RECOMMENDATION
R 286
IS0 SYSTEM OF LIMITS AND FITS
PART 1: GENERAL, TOLERANCES AND DEVIATIONS
1st EDITION
December 1962
COPYRIGHT RESERVED
The copyright of IS0 Recommendations and IS0 Standards
belongs to IS0 Member Bodies. Reproduction of these
documents, in any country, may be authorized therefore only
by the national standards organization of that country, being
a member of ISO.
For each individual country the only valid standard is the national standard of that country.
Printed in Switzerland
Also issued in French and Russian. Copies to be obtained through the national standards organizations.
---------------------- Page: 1 ----------------------
BRIEF HISTORY
The IS0 Recommendation R 286, IS0 System of Limits and Fits-Part I: General,
Tolerances and Deviations, was drawn up by Technical Committee ISO/TC 3, Limits and
Fits, the Secretariat of which is held by the Association Française de Normalisation
(AFNOR).
Work on this question by the Technical Committee began in 1949, taking into account
the studies which had been made by the former International Federation of the National
Standardizing Associations (ISA), and led, in 1957, to the adoption of a Draft IS0 Recom-
mendation.
all the
In January 1960, this Draft IS0 Recommendation (No. 321) was circulated to
IS0 Member Bodies for enquiry. It was approved by the following Member Bodies:
Australia Finland
Norway
Austria France Poland
Belgium Germany Romania
Brazil Hungary Spain
Bulgaria India Sweden
Burma Italy Switzerland
Japan
Chile United Kingdom
Czechoslovakia New Zealand Yugoslavia
Three Member Bodies opposed the approval of the Draft:
Netherlands, Portugal, U.S.S.R.
The Draft IS0 Recommendation was then submitted by correspondence to the IS0
Council, which decided, in December 1962, to accept it as an IS0 RECOMMENDATION.
-2-
---------------------- Page: 2 ----------------------
lSO/ R 286 . 1962 (E)
TABLE OF CONTENTS
Page
Introductory Note . 4
Foreword . 4
. . . .
1 GENERAL SYMBOLS DEFINITIONS 5
.........................
1.1 Scope of the IS0 System 5
..........................
1.2 Reference temperature 5
............................
1.3 Tolerances of parts 5
1.3.1 Notation . 6
1.4 Fits . 6
........... 8
1.5 Symbols for tolerances and deviations and symbols for fits
1.6 Vocabulary . 10
2 . TOLERANCES AND DEVIATIONS FOR SIZES
UP TO 500 mm (19.69 in) . 14
2.1 Formulae for tolerances and deviations . 14
2.1.1 Nominal diameter steps for metric and inch values . 14
2.1.2 Standard tolerances . 15
2.1.3 Fundamental deviations . 16
2.1.4 Rules for rounding off . 19
2.2 Numerical values . 20
(see also tables pages 22 to 26)
2.2.1 Standard IT tolerances . 20
2.2.2 Fundamental shaft deviations . 21
2.2.3 Hole deviations . 21
2.3 Commonly used shafts and holes . 27
(see also tables in Appendix)
2.3.1 General purposes . 27
2.3.2 Fine mechanisms and horology . 27
2.4 Justificatory note on the millimetre-inch correspondence . 27
3 . TOLERANCES AND DEVIATIONS FOR SIZES
ABOVE 500 mm UP TO 3150 mm (19.69 to 125 in) . 29
(Section 3 is given only as a provisional IS0 Recommendation)
3.1 Formulae for tolerances and deviations . 29
3.1.1 Nominal diameter steps for metric and inch values . 29
3.1.2 Tolerances . 29
3.1.3 Deviations . 30
3.1.4 Rules for rounding off . 31
3.2 Determination of limit deviations for each shaft or hole symbol . 32
3.2.1 Standard tolerances . 33
3.2.2 Fundamental shaft and hole deviations . 34
3.2.3 Important recommendations . 34
APPENDIX
TABLES OF COMMONLY USED SHAFTS AND HOLES
(see detailed summary at the beginning of the Appendix)
-3 .
---------------------- Page: 3 ----------------------
lSO/ R 286 - 1962 (E)
INTRODUCTORY NOTE
The values of the IS0 System of Limits and Fits are expressed
in metric units, for countries using the metric system of measurement,
in inch units, fqr countries using the inch system of measurement.
The IS0 System ensures complete fit interchangeability of parts manufactured to the
same symbol in one or other of these systems of measurement. However, in view of the
very slight numerical differences resulting from the conversion from millimetres into inches
(see clause 2.4), it is recommended that checking instruments calibrated in the system of
measurement in which the parts have been designed should be used, or that agreement
should be reached between suppliers and customers on the choice of the system of measure-
ment to be adopted for final inspection.
In the absence of any agreement to the contrary, the values in metric units will be taken
as authoritative in case of dispute regarding the choice of the system of measurement which
ought to have been adopted.
The same remarks apply in those borderline cases, an extremely rare class, in which
the nominal size falls within one diameter range in one system of measurement and within
the neighbouring range in the other system of measurement.
FOREWORD
The present IS0 Recommendation, IS0 System of Limifs and Fits, Part I, is based on the ISA System of
Limits and Fits published in ISA Bulletin 25 (1940), and on comments included in the Draft Final Report
of ISA Committee 3, December 1935.
This IS0 Recommendation differs from the ISA System in its lay-out and in the following main items:
1. Inclusion of sizes below 1 mm for grades up to grade 13.
2. Inclusion of the two grades O1 and O finer than grade 1.
3. Inclusion of new shaft and hole deviations:
cd, CD, ef, EF, fg, FG
up to 10 mm only . . . . . . . . for fine mechanisms and horology,
j, and Js . . . . . . . . . . . . . . providing a complete range of symmetrical deviations for
all diameter steps and all grades,.
za, ZA, zb, ZB, zc, ZC . . . . . . . for high interference fits.
4. Amendments of some standard tolerances for fine grades and of some deviations to connect the existing
values with those included in the above paragraphs. Numerical values amended with regard to those
deriving from the former ISA System are framed in a bold line in Table 7, page 22, Tables 8 and 9,
pages 23 to 26, and in the practical tables in the Appendix.
5. Inclusion of Tables 7, 8 and 9, permitting the easy calculations of the deviations corresponding to any
symbol through the whole range of diameter steps (upper and lower deviations).
It should be noted, however, that this possibility does not involve the use of all symbols. Indeed, in
addition to the exceptions mentioned above in point 3,
shafts and holes a A, b B are provided only for sizes above 1 mm;
shafts j8 are provided only for sizes up to 3 mm;
holes K, in grades above 8, are provided only for sizes up to 3 mm;
shafts and holes t T, v V, y Y are provided only for sizes from 24, 14 and 18 mm respectively (since,
below those sizes, they would only repeat adjoining symbols).
* The former deviations j and J have not in general been maintained in the fields where they were always sym-
metrical, since only deviations j, and Js are to be recommended for fits, for the sake of homogeneity. However,
a few symmetrical deviations j and one symmetrical deviation J have been maintained in grades 6 and 7.
-4-
---------------------- Page: 4 ----------------------
lSO/ R 286 - 1962 (E)
IS0 Recommendation R 286 Decem ber 1962
IS0 SYSTEM OF LIMITS AND FITS
PART I: GENERAL, TOLERANCES AND DEVIATIONS *
1. GENERAL - SYMBOLS - DEFINITIONS
1.1 Scope of the IS0 System
The IS0 System of Limits and Fits relates to tolerances on plain parts or components and to
the fits corresponding to their assembly.
For the sake of simplicity, and in view of the particular importance of cylindrical parts with
circular section, only these are referred to explicitly. It should be clearly understood however
that recommendations for this type of component apply equally well to other plain parts or
components; in particular, the general term " hole " or " shaft " can be taken as referring to
the space containing or contained by two parallel faces (or tangent planes) of any part, such as
the width of a slot, the thickness of a key, etc.
1.2 Reference temperature
As indicated by IS0 Recommendation R I,** the standard reference temperature is 20°C for
industrial measurements and, consequently, for dimensions defined by the System.
1.3 Tolerances of parts
Due mainly to the inevitable inaccuracy of manufacturing methods, a part cannot be made
precisely to a given dimension but, in order to meet its purpose, it is sufficient that it should be
made so as to lie within two permissible limits of size, the difference of which is the tolerance.
For the sake of convenience, a basic size is ascribed to the part and each of the two limits is
defined by its deviation from this basic size. The magnitude and sign of the deviation are obtained
by subtracting the basic size from the limit in question.
* This First Part relates only to the essential bases of the System, giving the prescribed limits of parts; it excludes al
matters of inspection or metrology, which will be dealt with in Part II of the System, covered by another IS0
Recommendation, at present under preparation.
** IS0 Recommendation R 1, Standard Reference Temperature for Industrial Length Measurements.
-5-
---------------------- Page: 5 ----------------------
lSO/ R 286 - 1962 (E)
~~~
Figure 1, which illustrates these definitions, is in practice replaced by a schematic diagram
similar to Figure 2 for the sake of simplicity. In this simplified schematic diagram, the axis of
the part, which is not represented, always lies, by convention, below the diagram. (In the example
illustrated, the two deviations of the shaft are negative and those of the hole positive.)
Hole
e//-///n Zero line
Shaft
FIG. 2
1.3.1 Notation
The following notation is used in this document: *
Upper deviation of a hole ES
Lower deviation of a hole E1
Upper deviation of a shaft es
Lower deviation of a shaft ei
1.4 Fits
When two parts are to be assembled, the relation resulting from the difference between their
sizes before assembly is called afit.
Depending upon the respective positions of the tolerance zones of the hole or the shaft, the fit
may be
a clearance fit,
a transitionjit
(i.e. such that the assembly may have either a clearance or an inter-
ference), or
an interference fit.
Figure 1 above shows a clearance fit, and Figure 3, page 7, shows the schematic diagram of
tolerance zones in various cases.
* However, it will be left to each country to adopt a notation more in accordance with its own language.
-6-
---------------------- Page: 6 ----------------------
lSO/ R 286 - 1962 (E)
Clearance fit
Shaft Shaft
trYvTF3
Transition Transition fits fits
Hole
Hole
Shaft Shaft
Shaft
Interference fit
FIG. 3
Two of the most commonly used methods of applying the IS0 System are the hole-basis system
and the shaft-basis system (defined under No. 1.6.38 and No. 1.6.39 in clause 1.6, “Vocabulary ”),
which are shown in Figure 4 below.
Shaft
Hole U)
.c!
U)
Examples taken from 2
Examples taken from
the hole- basis system
the shaft-basis system
FIG. 4
-7-
---------------------- Page: 7 ----------------------
lSO/ R 286 - 1962 (E)
1.5 Symbols for tolerances and deviations and symbols for fits
In order to satisfy the usual requirements both of individual parts and of fits, the System provides,
for any given basic size, a whole range of tolerances together with a whole range of deviations
defining the position of these tolerances with respect to the line of zero deviation, called the
zero line.
The tolerance, the value of which is a function of the basic size, is designated by a number
symbol, called the grade.
The position of the tolerance zone with respect to the zero line, which is a function of the basic
size, is indicated by a letter symbol (in some cases, two letters), a capital letter for holes, a small
letter for shafts (see Fig. 5).
The toleranced size is thus defined by its basic value followed by a “symbol” composed of a
letter (in some cases, two letters) and a number.
Example: 45 87.
A fit is indicated by the basic size common to both components, followed by symbol correspond-
ing to each component, the hole being quoted first.
HS
Example: 45 H8/g7 (possibly 45 H8-g7 or 45 -).
87
-8-
---------------------- Page: 8 ----------------------
lSO/ R 286 - 1962 (E)
HOLES
SHAFTS
FIG. 5.-Respective positions of the various tolerance zones
for a given diameter step
-9-
---------------------- Page: 9 ----------------------
iSO/ R 286 - 1962 (E)
1.6 Vocabulary *
1.6.1 Size.**-Number expressing in a particular unit the numerical value of a length.
(In French, the size is named cote, when it is inscribed on a drawing.)
1.6.2 Actual size (of a part).-Size as practically obtained (value which may be obtained by
measurement; see Part II of IS0 System of Limits and Fits).
1.6.3 Limits of size.-The two extreme permissible sizes of a part between which the actual
size should rie, the limits of size being included.
1.6.4 Maximum limit of size. -The
No. 1.6.10
greater of the two limits of size.
No. 7.6.9-, 7
1.6.5 Minimum limit of size. -The
smaller of the two limits of size.
1.6.6 Basic size.-Size by reference to
which the limits of size are fixed.
1.6.7 Deviation.-Algebraical difference between a size (actual, maximum, etc.) and the
corresponding basic size.
1.6.8 Actual deviation.-Algebraical difference between the actual size and the corresponding
basic size.
1.6.9 Upper deviation-Algebraical difference between the maximum limit of size and the
corresponding basic size.
1.6.10 Lower deviation.-Algebraical difference between the minimum limit of size and the
corresponding basic size.
1.6.11 Zero line.-In a graphical repre-
sentation of limits and fits, straight
No. 1.6.13
No. 1.6.14
line to which the deviations are
referred. The zero line is the line
I
of zero deviation and represents
A
the basic size. T
By convention, when the zero line is drawn horizontally, positive deviations are shown
above and negative deviations below it.
* It should be emphasized that some terms in the present vocabulary are defined, for the purposes of the IS0 System of
Limits and Fits, in a more restricted sense than that in common use.
** In particular, the word size is defined here as “size ofa length” (“dimension linéaire” in French), and the corresponding
French term “ dimension ” which, in current speech, has two meanings, corresponding respectively to the English
terms dimension ” and “ size ”, is here to be taken in the second sense only, viz. that of a numerical value.
- 10 -
---------------------- Page: 10 ----------------------
iSO/ R 286 - 1962 (E)
1.6.12 Tolerance.-Difference between the maximum limit of size and the minimum limit of
size (or, in other words, algebraical difference between the upper deviation and the
lower deviation).
The tolerance is an absolute value without sign.
1.6.13 Tolerance zone.-In a graphical representation of tolerances, zone comprised between
the two lines representing the limits of the tolerance and defined by its magnitude
(tolerance) and by its position in relation to the zero line.
1.6.14 Fundamental deviation.-That one of the two deviations which is conventionally chosen
to define the position of the tolerance zone in relation to the zero line.
1.6.15 Grade of tolerance.-In a standardized system of Limits and fits, group of tolerances
considered as corresponding to the same level of accuracy for all basic sizes.
1.6.16 Standard tolerance.-In a standardized system of limits and fits, any tolerance belonging
to the system.
1.6.17 Standard tolerance mit.-In the IS0 System of Limits and Fits, factor expressed only
in terms of the basic size and used as a basis for the determination of the standard
tolerances of the System. (Each tolerance is equal to the product of the value of the
standard tolerance unit, for the considered basic size, by a coefficient corresponding to
each grade of tolerance.)
1.6.18 Shaff.-Term used by convention to designate all external features of a part, including
parts which are not cylindrical.
1.6.19 Hole.-Term used by convention to designate all internal features of a part, iiicluding
parts which are not cylindrical.
1.6.20 Basic shuft.-In the IS0 System of Limits and Fits,
shaft the upper deviation of which is zero.
T
More generally, shaft chosen as a basis for a shaft-
basis system of fits (see No. 1.6.38).
1.6.21 Basic hole.-In the IS0 System of Limits and Fits,
hole the lower deviation of which is zero.
More generally, hole chosen as a basis for a hole-basis
kmA
system of fits (see No. 1.6.39).
1.6.22 Go limit.-Designation applied to that of the two limits of size which corresponds to
the maximum material condition, i.e. :
the upper limit of a shaft,
the lower limit of a hole.
(When limit gauges are used, this is the limit of size checked by the GO gauge.)
- 11 -
---------------------- Page: 11 ----------------------
lSO/ R 286 - 1962 (E)
1.6.23 NOT GO limit.-Designation applied to that of the two limits of size which corresponds
to the minimum material condition, i.e. :
the lower limit of a shaft,
the upper limit of a hole.
(When limit gauges are used, this is the limit of size checked by the NOT GO gauge.)
1.6.24 Fit.-Relationship resulting from the difference, before assembly, between the sizes
of the two parts which are to be assembled.
1.6.25 Basic size (of afit).-Common value of the basic size of the two parts of a fit.
1.6.26 Variation ofJit.-Arithmetical sum of the tolerances of the two mating parts of a fit.
1.6.27 Clearance.-Difference between
the sizes of the hole and the
shaft, before assembly, when this
difference is positive.
+NO. 1.6.28 1*6*27
1.6.28 Interference.-Magnitude of the
difference between the sizes of
the hole and the shaft, before
assembly, when this difference is
negative.
1.6.29 Clearance fit.-Fit which always
provides a clearance. (The toler-
Hole
ance zone of the hole is entirely
above that of the shaft.)
Shaft
1.6.30 Interference jt.-Fit which al-
ways provides an interference.
Shaft
(The tolerance zone of the hole
is entirely below that of the
Hole
shaft.)
1.6.31 Transition fit.-Fit which may
provide either a clearance or an
interference. (The tolerance zones
of the hole and the shaft over-
lap.)
- 12 -
-4
---------------------- Page: 12 ----------------------
ISO/R 286-1962(E)
1.6.32 Minimum clearance.-In a clear-
ance fit, difference between the
minimurn size of the hole and the
maximum size of the shaft.
Hole
Shaft
1.6.33 Maximum clearance.-In a clear-
ance or a transition fit, difference
between the maximum size of the
hole and the minimum size of the
shaft.
1.6.34 Minimum interference.-In an in-
terference fit, magnitude of the
Shaft
(negative) difference between the
maximum size of the hole and
I
I
the minimum size of the shaft,
t
before assembly.
Hole
1.6.35 Maximum interference.-In an
interference or a transition fit,
magnitude of the (negative) dif-
Shalt
ference between the minimum
size of the hole and the maxi-
mum size of the shaft, before
Hole Hole
assembly.
ï .6.36 Limit system.-System of standardized tolerances and deviations.
1.6.37 Fit system.-System of fits comprising shafts and holes belonging to a limit system.
1.6.38 Shaft-basis system offits.-System of fits in which the different clearances and inter-
ferences are obtained in associating various holes with a single shaft (or, possibly, with
shafts of different grades, but having the same fundamental deviation).
In the IS0 System, the basic shaft is the shaft the upper deviation of which is zero.
1.6.39 Hole-basis system offits.-System of fits in which the different clearances and inter-
ferences are obtained in associating various shafts with a single hole (or, possibly, with
holes of different grades, but having always the same fundamental deviation).
In the IS0 System, the basic hole is the hole the lower deviation of which is zero.
- 13 -
---------------------- Page: 13 ----------------------
ISO/ R 286 - 1962 (E)
2. TOLERANCES AND DEVIATIONS FOR SIZES UP TO 500 mm (19.69 in)
2.1 Formulae for tolerances and deviations
2.1.1 NominaI diameter steps for metric and inch values
For the sake of simplicity, the formulae given in clauses 2.1.2 and 2.1.3 for the calcula-
tion of standard tolerances and fundamental deviations are applied to suit the diameter
steps shown in Table 1 below; the results have been computed on the basis of the
geometrical mean D of the extreme diameters of each step and apply to all diameters
of this step.
For the whole of the step up to 3 mm (or 0.12 in), the average diameter is taken as
the geometrical mean of 1 and 3 mm (or 0.04 and 0.12 in).
TABLE 1. - Nominal diameter steps
Nominal diameter steps
Main steps Intermediate steps *
Inches
Millimetres I Inches
above
up to above 1 up to above up to I above up to
- 1 0.12
0.12 1 0.24
6 10 0.24 0.40
10 14 0.40 0.56
10 18 0.40 0.71
18 0.56
14 0.71
18 24 0.71 0.95
18 30 0.71 1.19
24 30 0.95
1.19
30 40
1.19 1.58
30 50 1.19
1.97
40 50 1.58 1.97
-
50 65 1.97 2.56
50 80 1.97 3.15
65 80 3.15
2.56
-
80 1 O0
3.15 3.94
SO 120 3.15 4.73
1 O0 120 3.94 4.73
120 140 4.73 5.52
4.73 7.09 140 160 5.52 6.30
160 180 6.30 7.09
180 200 7.09 7.88
7.09 200 225 7.88 8.86
225 250 9.85
8.86
11.03
250 250 9.85
9.85. 12.41
280 315 I 1 .O3 12.41
315 12.41 13.98
355
12.41
315 400 15.75
355 400 13.98 15.75
400 450 15.75 17.72
400 500 15.75 19.69
17.72 19.69
450 500
* These are used, in certain cases, when considered as necessary, for the deviations a to c and r to zc or A to C and R
to zc.
-14- .
---------------------- Page: 14 ----------------------
lSO/ R 286 - 1962 (E)
2.1.2 Standard tolerances
Eighteen grades of tolerance are provided, each corresponding to one of the tolerances,
known as the standard tolerances and called IT 01, IT O, IT 1 to IT 16, the numerical
values of which are given, for each nominal diameter step, in Table 7, page 22.
2.1.2.1 FOR GRADES 5 TO 16, the values are determined from the tolerance unit i, as follows:
when i is expressed in microns for D expressed in millimetres,
3
i = 0.45 fi + 0.001 D *
when i is expressed in 0.001 in for D expressed in inches,
3
i = 0.052 fi + 0.001 D
The values of the standard tolerances corresponding to grades 5 to 16 are given in
Table 2 below, in terms of the tolerance unit i:
TABLE 2. - Values of standard tolerances corresponding to grades 5 to 16
IT 5 IT 6 IT 7 IT 8 IT 9 IT 10 IT 11 IT 12 IT 13 IT 14 IT 15 IT 16
Values 1 7i 1 loi 16i I 25i 1 40i 1 64i I IOOi 160i 250i 400i 640i lOOOi
Nom.-Above IT 6, the tolerance is multiplied by 10 at each fifth step. ** This rule applies
also, if necessary, beyond IT 16.
2.1.2.2 FOR GRADES BELOW 5, the values are calculated as follows:
IT O1 IT O IT 1 I
I I I I
Value s in. ' microns '
I 0.3 +0.008 D I 0.5 +0.012 D
I 0.8 f-0.020 D
for D in millimetres
Values in 0.001 in
I 0.012+0.008 D 1 0.02+0.012 D 1 0.03+0.020 D
for D in inches
NoTE.-The values IT 2 to IT 4 have been scaled approximately geometrically between the
values of IT 1 and IT 5 (see Table 7, page 22).
* This formula has been empirically calculated on the basis of former national standards and taking account of the fact
that, for the same manufacturing conditions, the relationship between the values of the manufacturing errors and the
diameter is approximately a parabolic function.
** But for one exception : the value 7.5 is rounded off to 8 for grade 6 in the diameter step above 3 up to 6 mm.
- 15 -
---------------------- Page: 15 ----------------------
lSO/ R 286 - 1962 (E)
I
2.1.3 Fundamental deviations
Based on experiments, formulae had been accepted for the ISA System and admitted
as satisfactory; these formulae, indicated in clauses 2.1.3.1 and 2.1.3.2, permit the
calculation of the fundamental deviation for each case.
2.1.3.1 SHAFTS
For each letter symbol defining the position of the tolerance zone, the magnitude
and sign of one of the two deviations, which is known as the fundamental deviation
(upper deviation es or lower deviation ei) (see Fig. 1, page 6), are determined by
means of the formulae in Table 4, page 18.
The other deviation is derived from the first one, using the magnitude of the standard
tolerance IT, by means of the following algebraic relationship :
ei = es - IT or
es = ei + IT
It will be noted that
(I) except in the case of shafts j and js, for which, strictly speaking, there is no iunda-
mental deviation, the value of the deviation shown in Table 4 is independent
of the given grade (even if the formula includes a term involving IT) ;
(2) the fundamental deviation given by the formulae in the Table is, in principle,
that corresponding to the limit closest to the zero line, in other words,
the upper deviation es for shafts a to h and
the lower deviation ei for shafts j to zc.
2.1.3.2 HOLES
For each letter symbol, defining the position of the tolerance zone, the magnitude
and sign of the fundamental deviation (lower deviation ET for holes A to H and upper
deviation ES for holes J to ZC), are derived from the fundamental deviation es or ei
of the shaft with the same letter, according to the rules given below: *
The other deviation is derived from the first one, using the magnitude of the toler-
ance IT, by means of the following algebraic relationship :
ES = E1 + IT or
E1 = ES - 1T
* Those rules have :en I termine r the establis nent of the ISA System so
at,
(a) for holes complying with the general rule,
the limit corresponding to the fundamental deviation of a hole is exactly symmetrical, in relation to the zero
line, to the limit corresponding to the fundamental deviation of the shaft with the same letter;
(6) for holes complying with the special rule,
two comparable fits, with basic hole and basic shaft, in which a hole of a given grade is associated with a shaft
of the next finer grade (e.g. H7/p6 and P7/h6), have exactly the same clearances or interferences (see Fig. 6,
page 17).
- 16 -
---------------------- Page: 16 ----------------------
IS0 I R 286 - 1962 (E)
(I) General rule
~ ~~~
E1 = - es A to H
for
r ES = - ei for J to ZC
This rule is applicable to all deviations, except
(a) those to which the special rule given below applies,
(b) holes N for grades 9 to 16, above 3 mm (or 0.12 in), for which the fundamental deviation
ES = O.
(2) Special rule
ES = - ei + A
where A = difference IT, - ITn-, between the fundamental
tolerance of the grade in question and that of the
next finer grade
This rule is ipplicable, for diameter steps above 3 mm (or 0.12 in), to
J, K, M and N up to IT 8 inclusive,
P to zc up to IT 7 inclusive.
Hole-basis fit
FIG. 6
-17 -
---------------------- Page: 17 ----------------------
iSO/ R 286 - 1962 (E)
TABLE 4. - Formulae for fundamental shaft deviations
Upper deviation es Lower deviation ei
Values in microns Values in 0.001 in Values in microns Values in 0.001 in
for D in millimetres for D in inches for D in millimetres for D in inches
- - -(10.5 + 1.3 D:
- - --(265 + 1.3 D)
No formula
for D < 120 for D ,< 4.73 j8
k4
3 3
to
- - = + 0.6 _- _-
3.5 D
3.5 D
k7
for D > 120 for D > 4.73
k for
gra-
- - -(5.5 + 0.85 D)
L -(I40 + 0.85 D
des
=O
<3
îor D < 160 for D < 6.3
and
à8
-_
-
0 - 1.8 D 1.8 D
= + (IT7 - IT6)
for D> 160 for D > 6.3
I m I
I I I
for D < 1.58 1 p I= +IT7+0t05/= +IT7+OtoO.
= +75 + 0.8 0) 1 r. = Geometric mean of values ei
= -(95 + 0.8 D)
for p and s
for D > 40 for D > 1.58
I
for D < 50 for D < 1.97
= Geometric mean of values es
for c and d
for D > 50 for D > 1.97
- -- 16 DO.44
2.62
= + IT7 + 0.63 D
- -- 11 D0.41 1.63
=+IT7+D
= Geometric mean of values es
= + IT7 + 1.25 D
for e and f
= + IT7 + 1.6 D
= - 5.5 DO.41 - 0.82
=+IT7+2 D
I =
= Geometric mean of values es
= + IT7 + 2.5 D
for f and g
= + IT8 + 3.15 D
za I
_- - 2.5
0.3
=+IT9+4D
zb I
=O zc =+ITIO+5 D
IT
For j,: the two deviations are equal to rt -
2
- 18 -
---------------------- Page: 18 ----------------------
lSO/ R 286 - 1962 (E)
2.1.4 Rules for rounding off
2.1.4.1 METRIC VALUES
The values which result, in each diameter step, from the use of the formulae given
in clause 2.1.2 for the standard tolerances of grades 11 and finer, and those given
in Table 4, page 18, for fundamental shaft deviations, are rounded according to
the following rules :
TABLE 5. - Roundings of metric values
VALUES IN MICRONS
Values above
300 560 600 SO0 1000
Values up to
w 60 100 200 300 560 600 800 1000 2000
for standard
tolerances
1
10
for grades il
and finer
Rounding
in
for deviations es
multiples of
10 20 20 20 50
from a to g
I
t---
for deviations ei
from k to zc
NOTES
1. Values resulting from the sum or the difference of two values, which are both already
rounded, should not be rounded again.
2. For shafts js Special rounding-off rules are indicat
...