Toleranced dimensions — Conversion from inches into millimetres and vice versa

Dimensions tolérancées — Conversion d'inches en millimètres et réciproquement

Tolerirane mere - Pretvarjanje col v milimetre in obratno

General Information

Status
Withdrawn
Publication Date
30-Apr-1975
Withdrawal Date
30-Apr-1975
Current Stage
9599 - Withdrawal of International Standard
Completion Date
18-May-2000

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INTERNATIONAL STANDARD k
INTERNATIONAL ORGANIZATION FOR STANDARDIZATION NEXAYHAPOAHAS OPl-AHM3ALJWfl I-IO CTAHAAPTW3AI.@iM~ORGANISATION INTERNATIONALE DE NORMALISATION
Toleranced dimensions - Conversion from inches into
millimetres and vice versa
Dimensions tokrance’es
- Conversion finches en millim6 tres et re’ciproquemen t
First edition - 1975-05-15
UDC 389.151/.152
Ref. No. IS0 370-1975 (E)
Descriptors : tables (data), conversion of units, dimensions, dimensional tolerances, metric system.
Price based on 6 pages

---------------------- Page: 1 ----------------------
FOREWORD
IS0 (the International Organization for Standardization) is a worldwide federation
of national standards institutes (IS0 Member Bodies). The work of developing
International Standards is carried out through IS0 Technical Committees. Every
Member Body interested in a subject for which a Technical Committee has been set
up 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.
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.
Prior to 1972, the results of the work of the Technical Committees were published
as IS0 Recommendations; these documents are now in the process of being
transformed into International Standards. As part of this process, Technical
Committee ISO/TC 3 has reviewed IS0 Recommendation R 370 and found it
technically suitable for transformation. International Standard IS0 370 therefore
replaces IS0 Recommendation R 370-1964 to which it is technically identical.
IS0 Recommendation R 370 was approved by the Member Bodies of the following
countries :
Australia Greece Poland
Austria Hungary Portugal
Belgium India Romania
Canada I ran Spain
Chile Ireland Sweden
Czechoslovakia Italy Switzerland
Egypt, Arab Rep. of Japan Turkey
Finland Netherlands United Kingdom
France New Zealand Yugoslavia
Germany Norway
The Member Bodies of the followin g countries expressed disapproval of the
Recommendation on technical grounds
U.S.A.
U.S.S.R.
The Member Body of the following country disapproved the transformation of
ISO/R 370 into an International Standard :
France
0 International Organization for Standardization, 1975 l
Printed in Switzerland

---------------------- Page: 2 ----------------------
IS0 370-1975 (El
INTERNATIONAL STANDARD
Toleranced dimensions - Conversion from inches into
millimetres and vice versa
Consequently this method should be employed only when,
1 SCOPE AND FIELD OF APPLICATION
by special agreement, the original limits have to be
This International Standard specifies methods of conversion
respected absolutely (in particular, when components are to
of toleranced dimensions from inches into millimetres and
be inspected by means of origina12) gauges).
which ensure, under the most suitable
vice versa,
These two methods are specified in clauses 3 and 4, which
practical regard for interchangeability
conditions,
relate respectively to the conversion of inches into
corresponding to the specified tolerances.
millimetres and vice versa. They are supplemented by
various special methods of application (see clause 5).
2 GENERALITIES
Finally, there are annexes containing conversion tables
2.1 The use of the conversion factor 1 in = 25,4 mm
from inches into millimetres and vice versa, on the basis of
(exactly) I ) generally produces converted values containing
the conversion factor 1 in = 25,4 mm.
more decimal places than are required for the desired
accuracy.
3 CONVERSION OF INCHES INTO MILLIMETRES
It is therefore necessary to round these values suitably, in
accordance with the degree of accuracy of the toleranced
3.1 Method A (general rule)
dimensions, which depends on the magnitude of the
tolerance specified.
a) For each dimension in inches, consider only its two
limits, maximum and minimum.
2.2 Application of the rules for rounding, as given in
b) Convert the corresponding two values exactly into
tables 1 and 2, guarantees that even in the most
millimetres by means of the conversion factor :
unfavourable extreme cases neither of the two specified
1 in = 25,4 mm (see annex A).
limits will be exceeded by more than 2 to 2,5 % of the
value of the tolerance.
c) Round the results obtained in this way to the nearest
rounded value as indicated in table 1, depending on the
2.2.1 In method A, which is generally applicable, unless
original tolerance in inches, i.e. on the difference
expressly indicated to the contrary, the rounding is effected
betweenthe two limits in inches.3)
to the nearest rounded value so that, on the average, the
The use of this method guarantees that even in the most
converted tolerances remain statistically identical with the
unfavourable extreme cases neither of the two original
original tolerances.
limits will be exceeded by more than 2 % of the value of
The limits converted by this method are considered
the tolerance.
acceptable for interchangeability and serve as a basis for
inspection.
3.2 Method B (by special agreement)
2.2.2 In method B, rounding is effected systematically As method A, except that the rounding is not effected to
towards the interior of the tolerance zone so that, on the the nearest rounded value, but towards the interior of the
average, the converted tolerances are smaller than the tolerance (i.e. to the next lower value for the upper limit
original tolerances. and to the next higher value for the lower limit).
1) See ISO/R 31, Part I, No. I-3.h.
2) Gauges in the dimension to be converted.
3) This amounts to rounding each of the two values converted into miliimetres to a whole number of 1 X 10-n mm, when the original
tolerance in inches lies between 1 X 10-n and less than 10 X 10-n in.
1

---------------------- Page: 3 ----------------------
IS0 370-1975 (E)
This method shall be emp!oyed only when the original 4.2 Method B (by special agreement)
limits have to be respected absolutely (in particular, when
As method A, except that the rounding is not effected to
components are to be inspected by means of original
the nearest rounded value, but towards the interior of the
gauges).
tolerance (i.e. to the next lower value for the upper limit
TABLE 1 and to the next higher value for the lower limit).
This method shall be employed only when the original
Original tolerance in inches
Round off to a
I
limits have to be respected absolutely (in particular, when
whole number of
means of original
not less than and below components are to be inspected by
I I
gauges).
in in mm
TABLE 2
0.000 01 0.000 1
0,000 01
,
0.000 1 0.001 0,000 1
Original tolerance in millimetres
Round off to a
0.001 0.01 0,oo 1
whole number of
and below
0.01 0.1 0,Ol
0.1 1
0,1 in
mm
0,005 0.000 001
3.3 Example
0,05 0.000 01
03 0.000 1
Suppose that a dimension is expressed in inches as follows :
5 0.00 1
1.950 + 0.016 (= 1.966, 1.934)
50
0.01
4
Conversion of the two limits into millimetres gives
49,123 6 and 49,936 4
4.3 Example
As the tolerance equals 0.032 in and thus lies between 0.01
and 0.1 in, it is necessary, employing method A, to round
Suppose that a dimension is expressed in millimetres as
these values to the nearest 0,Ol mm. The values in
follows :
millimetres to be employed for these two limits are thus
49,5 + 0,4 (= 49,1, 49,9)
49,12 and 49,94
Conversion of the two limits into inches gives
(Rounding towards the interior of the tolerance, according
1.933 070 9 and 1.964 567 0
to method B, would give limits of 49,12 mm and
49,93 mm, i.e. a tolerance reduced to 0,80 mm instead of
As the tolerance equals 0,8 mm, and thus lies between 0,5
0,82 mm, as given by method A.)
and 5 mm, it is necessary, employing method A, to round
these values to the nearest 0.001 in. The values in inches to
be employed for these two limits are thus
4 CONVERSION OF MILLIMETRES INTO INCHES
1.933 and 1.965
4.1 Method A (general rule)
(Rounding towards the interior of the tolerance, according
a) For each dimension in millimetres consider only its
to method B, would give limits of 1.934
...

SLOVENSKI STANDARD
SIST ISO 370:1999
01-marec-1999
Tolerirane mere - Pretvarjanje col v milimetre in obratno
Toleranced dimensions -- Conversion from inches into millimetres and vice versa
Dimensions tolérancées -- Conversion d'inches en millimètres et réciproquement
Ta slovenski standard je istoveten z: ISO 370:1975
ICS:
17.040.10 Tolerance in ujemi Limits and fits
SIST ISO 370:1999 en
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

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

SIST ISO 370:1999

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

SIST ISO 370:1999
INTERNATIONAL STANDARD k
INTERNATIONAL ORGANIZATION FOR STANDARDIZATION NEXAYHAPOAHAS OPl-AHM3ALJWfl I-IO CTAHAAPTW3AI.@iM~ORGANISATION INTERNATIONALE DE NORMALISATION
Toleranced dimensions - Conversion from inches into
millimetres and vice versa
Dimensions tokrance’es
- Conversion finches en millim6 tres et re’ciproquemen t
First edition - 1975-05-15
UDC 389.151/.152
Ref. No. IS0 370-1975 (E)
Descriptors : tables (data), conversion of units, dimensions, dimensional tolerances, metric system.
Price based on 6 pages

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

SIST ISO 370:1999
FOREWORD
IS0 (the International Organization for Standardization) is a worldwide federation
of national standards institutes (IS0 Member Bodies). The work of developing
International Standards is carried out through IS0 Technical Committees. Every
Member Body interested in a subject for which a Technical Committee has been set
up 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.
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.
Prior to 1972, the results of the work of the Technical Committees were published
as IS0 Recommendations; these documents are now in the process of being
transformed into International Standards. As part of this process, Technical
Committee ISO/TC 3 has reviewed IS0 Recommendation R 370 and found it
technically suitable for transformation. International Standard IS0 370 therefore
replaces IS0 Recommendation R 370-1964 to which it is technically identical.
IS0 Recommendation R 370 was approved by the Member Bodies of the following
countries :
Australia Greece Poland
Austria Hungary Portugal
Belgium India Romania
Canada I ran Spain
Chile Ireland Sweden
Czechoslovakia Italy Switzerland
Egypt, Arab Rep. of Japan Turkey
Finland Netherlands United Kingdom
France New Zealand Yugoslavia
Germany Norway
The Member Bodies of the followin g countries expressed disapproval of the
Recommendation on technical grounds
U.S.A.
U.S.S.R.
The Member Body of the following country disapproved the transformation of
ISO/R 370 into an International Standard :
France
0 International Organization for Standardization, 1975 l
Printed in Switzerland

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

SIST ISO 370:1999
IS0 370-1975 (El
INTERNATIONAL STANDARD
Toleranced dimensions - Conversion from inches into
millimetres and vice versa
Consequently this method should be employed only when,
1 SCOPE AND FIELD OF APPLICATION
by special agreement, the original limits have to be
This International Standard specifies methods of conversion
respected absolutely (in particular, when components are to
of toleranced dimensions from inches into millimetres and
be inspected by means of origina12) gauges).
which ensure, under the most suitable
vice versa,
These two methods are specified in clauses 3 and 4, which
practical regard for interchangeability
conditions,
relate respectively to the conversion of inches into
corresponding to the specified tolerances.
millimetres and vice versa. They are supplemented by
various special methods of application (see clause 5).
2 GENERALITIES
Finally, there are annexes containing conversion tables
2.1 The use of the conversion factor 1 in = 25,4 mm
from inches into millimetres and vice versa, on the basis of
(exactly) I ) generally produces converted values containing
the conversion factor 1 in = 25,4 mm.
more decimal places than are required for the desired
accuracy.
3 CONVERSION OF INCHES INTO MILLIMETRES
It is therefore necessary to round these values suitably, in
accordance with the degree of accuracy of the toleranced
3.1 Method A (general rule)
dimensions, which depends on the magnitude of the
tolerance specified.
a) For each dimension in inches, consider only its two
limits, maximum and minimum.
2.2 Application of the rules for rounding, as given in
b) Convert the corresponding two values exactly into
tables 1 and 2, guarantees that even in the most
millimetres by means of the conversion factor :
unfavourable extreme cases neither of the two specified
1 in = 25,4 mm (see annex A).
limits will be exceeded by more than 2 to 2,5 % of the
value of the tolerance.
c) Round the results obtained in this way to the nearest
rounded value as indicated in table 1, depending on the
2.2.1 In method A, which is generally applicable, unless
original tolerance in inches, i.e. on the difference
expressly indicated to the contrary, the rounding is effected
betweenthe two limits in inches.3)
to the nearest rounded value so that, on the average, the
The use of this method guarantees that even in the most
converted tolerances remain statistically identical with the
unfavourable extreme cases neither of the two original
original tolerances.
limits will be exceeded by more than 2 % of the value of
The limits converted by this method are considered
the tolerance.
acceptable for interchangeability and serve as a basis for
inspection.
3.2 Method B (by special agreement)
2.2.2 In method B, rounding is effected systematically As method A, except that the rounding is not effected to
towards the interior of the tolerance zone so that, on the the nearest rounded value, but towards the interior of the
average, the converted tolerances are smaller than the tolerance (i.e. to the next lower value for the upper limit
original tolerances. and to the next higher value for the lower limit).
1) See ISO/R 31, Part I, No. I-3.h.
2) Gauges in the dimension to be converted.
3) This amounts to rounding each of the two values converted into miliimetres to a whole number of 1 X 10-n mm, when the original
tolerance in inches lies between 1 X 10-n and less than 10 X 10-n in.
1

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

SIST ISO 370:1999
IS0 370-1975 (E)
This method shall be emp!oyed only when the original 4.2 Method B (by special agreement)
limits have to be respected absolutely (in particular, when
As method A, except that the rounding is not effected to
components are to be inspected by means of original
the nearest rounded value, but towards the interior of the
gauges).
tolerance (i.e. to the next lower value for the upper limit
TABLE 1 and to the next higher value for the lower limit).
This method shall be employed only when the original
Original tolerance in inches
Round off to a
I
limits have to be respected absolutely (in particular, when
whole number of
means of original
not less than and below components are to be inspected by
I I
gauges).
in in mm
TABLE 2
0.000 01 0.000 1
0,000 01
,
0.000 1 0.001 0,000 1
Original tolerance in millimetres
Round off to a
0.001 0.01 0,oo 1
whole number of
and below
0.01 0.1 0,Ol
0.1 1
0,1 in
mm
0,005 0.000 001
3.3 Example
0,05 0.000 01
03 0.000 1
Suppose that a dimension is expressed in inches as follows :
5 0.00 1
1.950 + 0.016 (= 1.966, 1.934)
50
0.01
4
Conversion of the two limits into millimetres gives
49,123 6 and 49,936 4
4.3 Example
As the tolerance equals 0.032 in and thus lies between 0.01
and 0.1 in, it is necessary, employing method A, to round
Suppose that a dimension is expressed in millimetres as
these values to the nearest 0,Ol mm. The values in
follows :
millimetres to be employed for these two limits are thus
49,5 + 0,4 (= 49,1, 49,9)
49,12 and 49,94
Conversion of the two limits into inches gives
(Rounding towards the interior of the tolerance, according
1.933 070 9 and 1.964 567 0
to method B, would give limits of 49,12 mm and
49,93 mm, i.e. a tolerance reduced to 0,80 mm instead of
As the tolerance equals 0,8 mm, and thus lies between 0,5
0,82 mm, as given by method A.)
and 5 mm, it is necessary, employing method A, to round
these values to the nearest 0.001
...

NORME INTERNATIONALE 370
INTERNATIONAL ORGANIZATION FOR STANDARDlZATlON .ME)KAYHAPOAHA~ OPl-AHM3AL@iII I-IO CTAH~APTW3A~WW .ORGANISATION INTERNATIONALE DE NORMALISATION
Dimensions tobranc6es - Conversion d ’inches en miIIim6tres
et rkiproquement
Toleranced dimensions - Conversion from inches in to millime tres and vice versa
Premihre bdition - 1975-05-15
Rbf. no : IS0 370-1975 (F)
CDU 389.151/.152
tolkrance de dimension, systhme mbtrique.
Descripteurs : table de donnbes, conversion des unit&, dimension,
Prix bask sur 6 pages

---------------------- Page: 1 ----------------------
AVANT-PROPOS
L ’ISO (Organisation Internationale de Normalisation) est une federation mondiale
d ’organismes nationaux de normalisation (Comites Membres ISO). L ’elaboration de
Normes lnternationales est confide aux Comites Techniques ISO. Chaque Comite
Membre interesse par une etude a le droit de faire partie du Comite Technique
correspondant. Les organisations internationales, gouvernementales et non
gouvernementales, en liaison avec I ’ISO, participent egalement aux travaux.
Les Projets de Normes lnternationales adopt& par les Comites Techniques sont
soumis aux Comites Membres pour approbation, avant leur acceptation comme
Normes Internationales par le Conseil de I ’ISO.
Avant 1972, les resultats des travaux des Comites Techniques etaient publies
comme Recommandations ISO; maintenant, ces documents sont en tours de
transformation en Normes Internationales. Compte tenu de cette procedure, le
Comite Technique ISO/TC 3 a examine la Recommandation ISO/R 370 et est d ’avis
qu ’elle peut, du point de vue technique, etre transformee en Norme lnternationale.
La presente Norme lnternationale remplace done la Recommandation
ISO/R 370-1964 ;i laquelle elle est techniquement identique.
La Recommandation ISO/R 370 avait ete approuvee par les Comites Membres des
pays suivants :
Allemagne G r&e Pologne
Austral ie Wongrie Portugal
Autriche lnde Roumanie
Belgique Iran Royaume-Uni
Canada I rlande Suede
Chili ltalie Suisse
Egypte, Rep. arabe d’ Tchecoslovaquie
Japon
Espagne Norvege Turquie
Finlande Nouvelle-Zelande Yougoslavie
France
Pays-Bas
Les Comites Membres des pays suivants avaient desapprouve la Recommandation
pour des raisons techniques :
U. R.S.S.
U.S.A.
Le Comite Membre du Pays suivant a desapprouve la transformation de la
Recommandation ISO/R 370 en Norme lnternationale :
France
0 Organisation lnternationale de Normalisation, 1975 l
Imprim en Suisse

---------------------- Page: 2 ----------------------
NORME INTERNATIONALE IS0 370-1975 (F)
Dimensions tobrancbes - Conversion d ’inches en millimi%res
et rkiproquement
Iimites originales (en particulier, lorsque les pieces doivent
1 OBJET ET DOMAINE D ’APPLICATION
&t-e verifiees au moyen de calibres d ’origine*)).
La presente Norme lnternationale specific les methodes de
Ces deux methodes sont spkifiees dans les chapitres 3 et 4
conversion d ’inches en millimetres et reciproquement, des
dimensions tolerancees, permettant d ’assurer, dans les relatifs respectivement a la conversion des inches en
millimetres et reciproquement. Elles sont completees par di-
meilleures conditions, le respect pratique de I ’interchangea-
verses modalites particulieres d ’application (voir chapitre 5).
bilite correspondant aux tolerances prescrites.
Enfin, des annexes donnent les tables de conversion,
din&es en millimetres et reciproquement, sur la base du
2 GcN6RALITkS
facteur de conversion 1 in = 25,4 mm.
2.1 L ’emploi du facteur de conversion 1 in = 254 mm
(exactement) ‘) conduit generalement a des valeurs
converties comportant un plus grand nombre de decimales
que ne I ’exige la precision a atteindre.
3 CONVERSION DES INCHES EN MILLIMCTRES
II importe done d ’arrondir convenablement ces valeurs, en
fonction de la precision resultant, pour les dimensions
3.1 M6thode A (regle genet-ale)
tolerancees, de la valeur meme de la tolerance prescrite.
a) Considerer exclusivement, pour chaque dimension en
inches, chacune de ses deux Iimites, maximale et
2.2 L ’application des regles d ’arrondissage prevues aux
minimale.
tableaux 1 et 2 donne la garantie que, meme dans les cas
extremes les plus defavorables, aucune des deux Iimites
b) Convertir exactement, en millimetres, les deux
prescrites ne sera depassee de plus de 2 ou 2,5 % de la
valeurs correspondantes au moyen du facteur de
valeur de la tolerance.
conversion 1 in = 25,4 mm (voir annexe A).
c) Arrondir les resultats obtenus, au plus pres,
2.2.1 Dans la me ’thode A, valable d ’une facon generale,
,
conformement aux regles prevues au tableau 1, en
sauf indication contraire expresse, I ’arrondissage est
fonction de la tolerance originale en inches, c ’est-a-dire
de sorte que, en moyenne, les
effectue au plus prks,
de la difference entre les deux limites en inches.3)
tolerances converties restent statistiquement identiques aux
tolerances originales.
L ’application de cette methode donne la garantie que,
meme dans les cas extremes les plus defavorables, aucune
Les limites converties par cette methode, considerees
des deux limites originales ne sera depassee de plus de 2 %
comme acceptables pour I ’interchangeabilite, font foi pour
de la valeur de la tolerance.
la verification.
2.2.2 Dans la me ’thode B, I ’arrondissage est effect& 3.2 M6thode B (par derogation expresse)
systematiquement vers l ’intbrieur de la zone de tolerance,
Proceder comme il est specific dans la methode A,
de sorte que, en moyenne, les tolerances converties sont
toutefois, effectuer I ’arrondissage, non pas au plus prits,
plus reduites que les tolerances originales prescrites.
mais vers I ’interieur de la tolerance (c ’est-a-dire a la valeur la
Cette methode ne doit done etre appliquee, par derogation plus voisine vers le bas pour la Iimite superieure et vers le
expresse, qu ’en cas de nkessite de respect absolu des haut pour la limite inferieure).
1) Voir ISO/R 31, Partie I, no l-3.h.
2) Calibres correspondant A la dimension a convertir.
3) Ceci revient 6 arrondir chacune des deux valeurs converties en miIIim6tres ;i un nombre entier de 1 X lo-” mm, quand la tolkrance originale
en inches est comprise entre 1 X 10-n et moins de 10 X 10-n in.
1

---------------------- Page: 3 ----------------------
IS0 3704975 (F)
L ’application de cette methode donne la garantie que,
Cette methode ne doit etre appliquee qu ’en cas de necessite
meme dans les cas extremes les plus defavorables, aucune
de respect absolu des Ii-mites originales (en particulier,
des deux Iimites originales ne sera depassee de plus de 2,5 %
Iorsque les pieces doivent etre verifiees au moyen de
de la valeur de la tolerance.
calibres d ’origine).
TABLEAU 1
4.2 M6thode B (par derogation expresse)
T ”lhance 0 ’“;“” e;;;*yIl;e ~ 1 ntzzti;rde
Proceder comme il est specific dans la methode A,
;upCrieure ou Cgale i
toutefois, effectuer I ’arrondissage, non pas au plus pres,
in in mm mais vers I ’interieur de la tolerance (c ’est-h-dire a la valeur la
plus voisine vers le bas pour la limite superieure et vers le
0,000 01 0,000 1
0,000 01
haut pour la limite inferieure).
0,000
1 0,001 0,000 1
Cette methode ne doit etre appliquee qu ’en cas de necessite
0,001 0,Ol 0,001
de respect absolu des Iimites originales (en particulier,
0,Ol 091 0,Ol
Iorsque les pieces doivent etre verifiees au moyen de
091 1
091 calibres d ’origine).
3.3 Exemple
TABLEAU 2
.
#
Soit une dimension s ’exprimant en inches comme suit :
Tolkrance originale en millimhres
Arrondir i un
1,950 + 0,016 (= 1,966, 1,934)
nombre entier de
supirieure ou &gale i infhieure i
La conversion, en millimetres, des deux Iimites donne
mm mm in
49,123 6 et 49,936 4
I
0,000 001
La tolerance etant egale a 0,032 in et comprise par 0,000 5 0,005
consequent entre 0,Ol et 0,l in, il faut, selon la methode A,
0,05 0,000 01
0,005
arrondir au plus pres a 0,Ol mm. Les valeurs h retenir pour
0,000 1
0,05
OS
les deux limites, en millimetres, sont done
5 0,oo 1
095
49,12 et 49,94
50 0,Ol
5
*
(L ’arrondissage vers I ’interieur de la tolerance, selon la
methode B, donnerait les Iimites 49,13 mm et 49,93 mm,
soit une tolerance reduite a 0,80 mm au lieu de 0,82 mm
donnee par la methode A.)
4.3 Exemple
Soit une dimension s ’exprimant en millimetres comme
4 CONVERSION DES MILLIMETRES EN INCHES
suit :
49,5 + 0,4 (= 49,1,49,9)
4.1 Mdthcde A (regle generale)
La conversion, en inches, des deux Iimites donne
a) Considerer exclusivement, pour chaque dimension en
millimetres, chacune de ses deux limites, maximale et
1,933 070 9 et 1,964 567 0
minimale.
La tolerance etant egale a 0,8 mm et comprise par
b) Convertir, en inches, les deux valeurs
consequent entre 0,5 et 5 mm, il faut, selon la methode A,
correspondantes au moyen des tables de conversion
arrondir au plus pres a 0,001 in. Les valeurs a retenir pour
donnees dans l ’annexe B (sur la base du facteur de
les deux limites, en inches, sont done
conversion 1 mm = l/25,4 in).
1,933 et 1,965
c) Arrondir les resultats obtenus, au plus pres,
(L ’arrondissage vers I ’interieur de la tolerance, selon la
conformement aux regles prevues au tableau 2, en
methode B, donnerait les limites 1,934 in et 1,964 in, soit
fonction de’ la tolerance originale en millimetres,
une tolerance reduite a 0,030 in au lieu de 0,032 in donnee
c ’est-&dire de la difference entre les deux limites en
par la methode A.)
millimetresl).
1) P
...

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