Castings -- System of dimensional tolerances and machining allowances

Applies to cast metals and their alloys produced by various casting manufacturing processes. Is applicable both to general tolerances and/or required machining allowances given on a drawing and to individual tolerances and/or required machining allowances which are shown immediately following a specific dimension. The system specified applies when the foundry provides the pattern or die equipment or accepts responsibility for proving it.

Pièces moulées -- Système de tolérances dimensionnelles et surépaisseurs d'usinage

Ulitki - Sistem toleranc mer in dodatki za mehansko obdelavo

General Information

Status
Withdrawn
Publication Date
31-Oct-1995
Withdrawal Date
13-Nov-2013
Current Stage
9900 - Withdrawal (Adopted Project)
Start Date
14-Nov-2013
Due Date
07-Dec-2013
Completion Date
14-Nov-2013

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Standards Content (Sample)

IS0
INTERNATIONAL
8062
STANDARD
Second edition
I 994-04-01
Castings - System of dimensional
tolerances and machining allowances
Pi&es moul&es - Systhme de tokrances dimensionnelies et
sur6paisseurs d ‘usinage
Reference number
IS0 8062: 1994(E)

---------------------- Page: 1 ----------------------
IS0 8062: 1994(E)
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 member body interested in a subject for
which a technical committee has been established has the right to be
represented on that committee. International organizations, governmental
and non-governmental, in liaison with ISO, also take part in the work. IS0
collaborates closely with the International Electrotechnical Commission
(I EC) on all matters of electrotechnical standardization.
Draft International Standards adopted by the technical committees are
circulated to the member bodies for voting. Publication as an International
Standard requires approval by at least 75 % of the member bodies casting
a vote.
International Standard IS0 8062 was prepared by Technical Committee
lSO/TC 3, Limits and fits.
This second edition cancels and replaces the first edition
(IS0 8062:1984), which has been technically revised.
Annexes A, B and C of this International Standard are for information only.
0 IS0 1994
All rights reserved. Unless otherwise specified, no part of this publication may be reproduced
or utilized in any form or by any means, electronic or mechanical, including photocopying and
microfilm, without permission in writing from the publisher.
International Organization for Standardization
Case Postale 56 l CH-1211 Geneve 20 l Switzerland
Printed in Switzerland
ii

---------------------- Page: 2 ----------------------
0 IS0
IS0 8062: 1994(E)
Introduction
This International Standard relates to a system of tolerance grades and
machining allowance grades for cast metals and their alloys.
The tolerance specified for a casting may determine the casting method.
It is therefore recommended, before the design or the order is finalized,
that the customer liaise with the foundry to discuss
the proposed casting design and accuracy required;
a)
machining requirements;
b)
c) method of casting;
the number of castings to be manufactured;
d)
the casting equipment involved;
e)
f) any special requirements, for instance, datum target systems, individ-
ual dimensional tolerances, geometrical tolerances, fillet radii toler-
ances and individual machining allowances;
whether any other standard is more appropriate for the casting.
9)
NOTE 1
Further investigation on metallic permanent moulds (gravity- and low-
pressure), pressure die castings and investment castings should be carried out.
Because the dimensional accuracy of a casting is related to production
factors, tolerance grades which can be achieved for various methods and
metals are described in annex A for
a) long series and mass production, where development, adjustment and
maintenance of casting equipment make it possible to achieve close
tolerances;
short series and single production.
b)
Information on typical required machining allowance grades is given in
annex B.

---------------------- Page: 3 ----------------------
This page intentionally left blank

---------------------- Page: 4 ----------------------
IS0 8062: 1994(E)
INTERNATIONAL STANDARD 0 IS0
Castings - System of dimensional tolerances and
machining allowances
IS0 286-l : 1988, IS0 system of limits and fits -
1 Scope
Part I: Bases of tolerances, deviations and fits.
This International Standard specifies a system of tol-
IS0 1302:1992, Technical drawings - Method of in-
erance grades and required machining allowance
dicating s&ace texture.
grades for the dimensions of castings. It is applicable
to the dimensions of cast metals and their alloys
produced by various casting manufacturing processes
[but see also Introduction g) and clause 51.
This tnternational Standard applies both to general
3 Definitions
tolerances and/or required machining allowances
given on a drawing and to individual tolerances
For the purposes of this International Standard, the
and/or required machining allowances which are
following definitions apply.
shown immediately following a specific dimension
(see clause 11).
3.1 basic dimension: Dimension of a raw casting
before machining (see figure I), the necessary ma-
The system specified applies when the foundry pro-
chining allowance being included (see figure 2).
vides the pattern or die equipment or accepts re-
sponsibility for proving it.
Raw casting basic dimension
1
2 Normative references
---
The following standards contain provisions which,
through reference in this text, constitute provisions
.
of this International Standard. At the time of publi-
cation, the editions indicated were valid. All standards
are subject to revision, and parties to agreements
based on this International Standard are encouraged
to investigate the possibility of applying the most re-
cent editions of the standards indicated below.
Members of IEC and IS0 maintain registers of cur-
rently valid International Standards. Figure 1 - Drawing indications (see clause 4)
1

---------------------- Page: 5 ----------------------
0 IS0
IS0 8062: 1994(E)
With cylindrical features or machining on both sides,
the RMA is taken into account twice (see figures 5
and 6).
Finished dimension
3.4 mismatch: Relative displacement of surfaces of
,
a casting owing to inaccuracies in the constituent
parts of multipart moulds (see figure3).
RMA-
3.5 draft angle (taper): Additional slope of shaping
elements (e.g. on enveloping surfaces) necessary to
facilitate the removal of a casting from a mould or die,
or a pattern from a mould, or the parts of a permanent
mould from each other.
CT/2
4 Dimensioning
With the exception of dimensioning of wall thickness
Minimum limit of size
(where a chain of two dimensions may exist), chain
Maximum limit of size
- dimensioning shall be avoided.
I
5 Tolerance grades
Figure 2 - Tolerance limits
There are 16 casting tolerance grades, designated
CT1 to CT16 (see table 1).
Dimensions for which general tolerances are not
3.2 dimensional tolerance: [See IS0 286-I].
suitable shall be allocated individual tolerances.
While work is proceeding to obtain definite tolerance
3.3 required machining allowance, RMA: On raw
information for metallic permanent mould castings
castings, a material allowance to permit the removal
of the effects of casting on the surface by subsequent (gravity- and low-pressure), pressure die castings and
machining and to allow the achievement of the de- investment castings, other more appropriate tolerance
standards, e.g. national standards, may be employed
sired surface texture and the necessary accuracy of
for these particular processes.
dimension.
Maximum mismatch , _ Maximum mismatch
Minimum Limit of size
Ir= Z
Maximum limit of size
-c m
Figure 3 - Maximum mismatch

---------------------- Page: 6 ----------------------
0 IS0
IS0 8062:1994(E)
thickness in grades CT1 to CT15 shall be one grade
6 Mismatch
coarser than the general tolerance for other dimen-
Unless otherwise specified, mismatch shall lie within sions; for example, if there is a general tolerance on
the tolerance shown in table 1 (see figure3). When it a drawing of CTlO, the tolerance on wall thicknesses
is important to restrict further the value of mismatch, shall be CT? 1.
the maximum value shall be stated on the drawing
(see 11 .I).
8 Tapered features
7 Wall thickness Where a design requires a tapered feature (e.g. fea-
ture with a draft angle), the tolerance shall be applied
Unless otherwise specified, the tolerance for wall symmetrically along the surface (see figure4).
Drawina indication
Interpretation
$= Ejxic dimension-]
Basic dimension
Taper +
Taper -
b)
Taper *
Figure 4 -
Tolerance zone on tapered features
3

---------------------- Page: 7 ----------------------
@J IS0
IS0 8062:1994(E)
The drawing shall specify generally whether the taper When agreed between manufacturer and purchaser
the tolerance zone may be
shall be added to, subtracted from or averaged to the for specific reasons,
material, e.g. asymmetric. In such a case the tolerance shall be
stated individually, following the basic dimension.
taper +, figure4a)
taper -, figure 4 b)
10 Required machining allowances,
RMA
taper *, figure4c)
Tapers for particular surfaces arranged differently
from the general arrangement of taper of the drawing 10.1 General
shall be indicated individually at the surface, e.g.
Unless otherwise specified, the required machining
d
+ l allowance is valid for the entire raw casting, i.e. only
one value is specified for all surfaces to be machined,
For dimensions to be machined, “taper +” shall be
and this shall be selected from the appropriate di-
applied, irrespective of the general drawing specifica-
mension range according to the largest overall di-
tion for taper, in order that the finished dimensions
mension of the finished casting after final machining
can be achievable.
(see figure 9).
The maximum dimension of a feature, as cast, shall
9 Position of tolerance zone
not exceed the finished dimension plus the required
machining allowance plus the total casting tolerance
The tolerance zone, unless otherwise stated, shall be
(see figure 2 and figures 5 to 8). When applicable, the
symmetrically disposed with respect to a basic di-
taper shall be considered additionally, as shown in
mension, i.e. with one half on the positive side and
figure 4.
one half on the negative side (see figure2).
CT/4,_ + /-CT/4
F RMA
RMA
1 e
I
I
R=F+ZRMA+CT/Z
R = Raw casting basic dimension
F = Dimension after final machining
RMA = Required machining allowance
CT = Casting tolerance
Figure 5 - External machining of boss

---------------------- Page: 8 ----------------------
F
- -
CT/4
CT/4 R
r'
C
RMA RMA
--c -
*
R=F-ZRMA-CT/Z
CT/Z CT/2
I-- --I
Internal machining
Figure 6 -
R=F
(= F - RMA + RMA - CT/4 + CT/4)
CT/Z CT/2
I-- L-l
Figure 7 - Machining of step dimension
R=F+RMA+CT/Z
Figure 8 - Machining on one side of feature
5

---------------------- Page: 9 ----------------------
0 IS0
IS0 8062: 1994(E)
b) if further restriction of the mismatch is required
(see clause 4);
EXAMPLE
“General tolerances IS0 8062 - CT12 - maxi-
mum mismatch 1,5”
if individual tolera rices are required fol
...

SLOVENSKI STANDARD
SIST ISO 8062:1995
01-november-1995
Ulitki - Sistem toleranc mer in dodatki za mehansko obdelavo
Castings -- System of dimensional tolerances and machining allowances
Pièces moulées -- Système de tolérances dimensionnelles et surépaisseurs d'usinage
Ta slovenski standard je istoveten z: ISO 8062:1994
ICS:
17.040.10 Tolerance in ujemi Limits and fits
SIST ISO 8062:1995 en
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

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

SIST ISO 8062:1995

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

SIST ISO 8062:1995
IS0
INTERNATIONAL
8062
STANDARD
Second edition
I 994-04-01
Castings - System of dimensional
tolerances and machining allowances
Pi&es moul&es - Systhme de tokrances dimensionnelies et
sur6paisseurs d ‘usinage
Reference number
IS0 8062: 1994(E)

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

SIST ISO 8062:1995
IS0 8062: 1994(E)
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 member body interested in a subject for
which a technical committee has been established has the right to be
represented on that committee. International organizations, governmental
and non-governmental, in liaison with ISO, also take part in the work. IS0
collaborates closely with the International Electrotechnical Commission
(I EC) on all matters of electrotechnical standardization.
Draft International Standards adopted by the technical committees are
circulated to the member bodies for voting. Publication as an International
Standard requires approval by at least 75 % of the member bodies casting
a vote.
International Standard IS0 8062 was prepared by Technical Committee
lSO/TC 3, Limits and fits.
This second edition cancels and replaces the first edition
(IS0 8062:1984), which has been technically revised.
Annexes A, B and C of this International Standard are for information only.
0 IS0 1994
All rights reserved. Unless otherwise specified, no part of this publication may be reproduced
or utilized in any form or by any means, electronic or mechanical, including photocopying and
microfilm, without permission in writing from the publisher.
International Organization for Standardization
Case Postale 56 l CH-1211 Geneve 20 l Switzerland
Printed in Switzerland
ii

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

SIST ISO 8062:1995
0 IS0
IS0 8062: 1994(E)
Introduction
This International Standard relates to a system of tolerance grades and
machining allowance grades for cast metals and their alloys.
The tolerance specified for a casting may determine the casting method.
It is therefore recommended, before the design or the order is finalized,
that the customer liaise with the foundry to discuss
the proposed casting design and accuracy required;
a)
machining requirements;
b)
c) method of casting;
the number of castings to be manufactured;
d)
the casting equipment involved;
e)
f) any special requirements, for instance, datum target systems, individ-
ual dimensional tolerances, geometrical tolerances, fillet radii toler-
ances and individual machining allowances;
whether any other standard is more appropriate for the casting.
9)
NOTE 1
Further investigation on metallic permanent moulds (gravity- and low-
pressure), pressure die castings and investment castings should be carried out.
Because the dimensional accuracy of a casting is related to production
factors, tolerance grades which can be achieved for various methods and
metals are described in annex A for
a) long series and mass production, where development, adjustment and
maintenance of casting equipment make it possible to achieve close
tolerances;
short series and single production.
b)
Information on typical required machining allowance grades is given in
annex B.

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

SIST ISO 8062:1995
This page intentionally left blank

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

SIST ISO 8062:1995
IS0 8062: 1994(E)
INTERNATIONAL STANDARD 0 IS0
Castings - System of dimensional tolerances and
machining allowances
IS0 286-l : 1988, IS0 system of limits and fits -
1 Scope
Part I: Bases of tolerances, deviations and fits.
This International Standard specifies a system of tol-
IS0 1302:1992, Technical drawings - Method of in-
erance grades and required machining allowance
dicating s&ace texture.
grades for the dimensions of castings. It is applicable
to the dimensions of cast metals and their alloys
produced by various casting manufacturing processes
[but see also Introduction g) and clause 51.
This tnternational Standard applies both to general
3 Definitions
tolerances and/or required machining allowances
given on a drawing and to individual tolerances
For the purposes of this International Standard, the
and/or required machining allowances which are
following definitions apply.
shown immediately following a specific dimension
(see clause 11).
3.1 basic dimension: Dimension of a raw casting
before machining (see figure I), the necessary ma-
The system specified applies when the foundry pro-
chining allowance being included (see figure 2).
vides the pattern or die equipment or accepts re-
sponsibility for proving it.
Raw casting basic dimension
1
2 Normative references
---
The following standards contain provisions which,
through reference in this text, constitute provisions
.
of this International Standard. At the time of publi-
cation, the editions indicated were valid. All standards
are subject to revision, and parties to agreements
based on this International Standard are encouraged
to investigate the possibility of applying the most re-
cent editions of the standards indicated below.
Members of IEC and IS0 maintain registers of cur-
rently valid International Standards. Figure 1 - Drawing indications (see clause 4)
1

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

SIST ISO 8062:1995
0 IS0
IS0 8062: 1994(E)
With cylindrical features or machining on both sides,
the RMA is taken into account twice (see figures 5
and 6).
Finished dimension
3.4 mismatch: Relative displacement of surfaces of
,
a casting owing to inaccuracies in the constituent
parts of multipart moulds (see figure3).
RMA-
3.5 draft angle (taper): Additional slope of shaping
elements (e.g. on enveloping surfaces) necessary to
facilitate the removal of a casting from a mould or die,
or a pattern from a mould, or the parts of a permanent
mould from each other.
CT/2
4 Dimensioning
With the exception of dimensioning of wall thickness
Minimum limit of size
(where a chain of two dimensions may exist), chain
Maximum limit of size
- dimensioning shall be avoided.
I
5 Tolerance grades
Figure 2 - Tolerance limits
There are 16 casting tolerance grades, designated
CT1 to CT16 (see table 1).
Dimensions for which general tolerances are not
3.2 dimensional tolerance: [See IS0 286-I].
suitable shall be allocated individual tolerances.
While work is proceeding to obtain definite tolerance
3.3 required machining allowance, RMA: On raw
information for metallic permanent mould castings
castings, a material allowance to permit the removal
of the effects of casting on the surface by subsequent (gravity- and low-pressure), pressure die castings and
machining and to allow the achievement of the de- investment castings, other more appropriate tolerance
standards, e.g. national standards, may be employed
sired surface texture and the necessary accuracy of
for these particular processes.
dimension.
Maximum mismatch , _ Maximum mismatch
Minimum Limit of size
Ir= Z
Maximum limit of size
-c m
Figure 3 - Maximum mismatch

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

SIST ISO 8062:1995
0 IS0
IS0 8062:1994(E)
thickness in grades CT1 to CT15 shall be one grade
6 Mismatch
coarser than the general tolerance for other dimen-
Unless otherwise specified, mismatch shall lie within sions; for example, if there is a general tolerance on
the tolerance shown in table 1 (see figure3). When it a drawing of CTlO, the tolerance on wall thicknesses
is important to restrict further the value of mismatch, shall be CT? 1.
the maximum value shall be stated on the drawing
(see 11 .I).
8 Tapered features
7 Wall thickness Where a design requires a tapered feature (e.g. fea-
ture with a draft angle), the tolerance shall be applied
Unless otherwise specified, the tolerance for wall symmetrically along the surface (see figure4).
Drawina indication
Interpretation
$= Ejxic dimension-]
Basic dimension
Taper +
Taper -
b)
Taper *
Figure 4 -
Tolerance zone on tapered features
3

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

SIST ISO 8062:1995
@J IS0
IS0 8062:1994(E)
The drawing shall specify generally whether the taper When agreed between manufacturer and purchaser
the tolerance zone may be
shall be added to, subtracted from or averaged to the for specific reasons,
material, e.g. asymmetric. In such a case the tolerance shall be
stated individually, following the basic dimension.
taper +, figure4a)
taper -, figure 4 b)
10 Required machining allowances,
RMA
taper *, figure4c)
Tapers for particular surfaces arranged differently
from the general arrangement of taper of the drawing 10.1 General
shall be indicated individually at the surface, e.g.
Unless otherwise specified, the required machining
d
+ l allowance is valid for the entire raw casting, i.e. only
one value is specified for all surfaces to be machined,
For dimensions to be machined, “taper +” shall be
and this shall be selected from the appropriate di-
applied, irrespective of the general drawing specifica-
mension range according to the largest overall di-
tion for taper, in order that the finished dimensions
mension of the finished casting after final machining
can be achievable.
(see figure 9).
The maximum dimension of a feature, as cast, shall
9 Position of tolerance zone
not exceed the finished dimension plus the required
machining allowance plus the total casting tolerance
The tolerance zone, unless otherwise stated, shall be
(see figure 2 and figures 5 to 8). When applicable, the
symmetrically disposed with respect to a basic di-
taper shall be considered additionally, as shown in
mension, i.e. with one half on the positive side and
figure 4.
one half on the negative side (see figure2).
CT/4,_ + /-CT/4
F RMA
RMA
1 e
I
I
R=F+ZRMA+CT/Z
R = Raw casting basic dimension
F = Dimension after final machining
RMA = Required machining allowance
CT = Casting tolerance
Figure 5 - External machining of boss

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

SIST ISO 8062:1995
F
- -
CT/4
...

IS0
NORME
8062
INTERNATIONALE
Deuxihme 6dition
1994-04-01
- SystQme de tobrances
Pikes moulbes
dimensionnelles et surbpaisseurs d ’usinage
System of dimensional tolerances and machining allowances
Castings -
Mm&o de rbfbrence
IS0 8062: 1994(F)

---------------------- Page: 1 ----------------------
IS0 8062: 1994(F)
Avant-propos
L ’ISO (Organisation internationale de normalisation) est une federation
mondiale d ’organismes nationaux de normalisation (comites membres de
I’ISO). L ’elaboration des Normes internationales est en general confiee aux
comites techniques de I’ISO. Chaque comite membre inter-es& par une
etude a le droit de faire partie du comite technique tree a cet effet. Les
organisations internationales, gouvernementales et non gouvernemen-
tales, en liaison avec I’ISO participent egalement aux travaux. L ’ISO colla-
bore etroitement avec la Commission electrotechnique internationale (CEI)
en ce qui concerne la normalisation electrotechnique.
Les projets de Normes internationales adopt& par les comites techniques
sont soumis aux comites membres pour vote. Leur publication comme
Normes internationales requiert I’approbation de 75 % au moins des co-
mites membres votants.
La Norme internationale IS0 8062 a ete elaboree par le comite technique
lSO/TC 3, Ajustements.
Cette deuxieme edition annule et remplace la premiere edition
(IS0 8062:1984), dont elle constitue une revision technique.
Les annexes A, B et C de la presente Norme internationale sont donnees
uniquement a titre d ’information.
0 IS0 1994
Droits de reproduction reserves. Sauf prescription differente, aucune partie de cette publi-
cation ne peut Qtre reproduite ni utilisee sous quelque forme que ce soit et par aucun pro-
cede, electronique ou mecanique, y compris la photocopie et les microfilms, sans I ’accord
ecrit de I ’editeur.
Organisation internationale de normalisation
Case Postale 56 l CH-1211 Geneve 20 l Suisse
Imprime en Suisse
ii

---------------------- Page: 2 ----------------------
Introduction
La presente Norme internationale se rapporte a un systeme de tolerances
et de surepaisseurs d ’usinage pour les pieces moulees en metal et leurs
alliages.
La tolerance specifiee pour une piece moulee peut determiner la methode
de moulage. II est done recommande, avant que le dessin ne soit trace
definitivement ou la commande pas&e, que le client coop&e avec la
fonderie pour convenir
a) du trace de piece propose et de la precision demandee;
b) des exigences d ’usinage;
c) de la methode de moulage;
d) du nombre de pieces moulees a realiser;
e) de I ’outillage de fonderie necessaire;
f) des exigences speciales concernant, par exemple, les systemes de
reference, les tolerances dimensionnelles individuelles, les tolerances
geometriques, les tolerances de rayons de raccordement et les sur-
epaisseurs d ’usinage individuelles;
g) de toute autre norme plus appropriee pour la piece.
NOTE 1 II convient d ’effectuer des recherches suppl6mentaires pour le mou-
lage en moule m&allique permanent (gravit6 et basse pression), la coulke sous
pression et le moulage de prkision.
La precision dimensionnelle d ’une piece moulee &ant fonction des fac-
teurs de production, les classes de tolerance realisables selon les metho-
des et les metaux sont donnees dans I ’annexe A pour
a) la production en grandes series et de masse, ou la conception, le re-
glage et la maintenance de I ’outillage rendent possible des tolerances
serrees;
b) la production en petites series et unitaire.
Des informations sur les classes typiques de surepaisseurs d ’usinage
specifiees sont donnees dans l ’annexe B.
. . .
III

---------------------- Page: 3 ----------------------
NORME INTERNATIONALE 0 IS0 IS0 8062: 1994(F)
i&es moukes - Systhme de tolhrances
imensionnelles et surbpaisseurs d ’usinage
IS0 286-l :1988, Syst&me IS0 de tolbances et
1 Domaine d ’application
Partie 1: Base des tokances,
d ’ajustements -
&arts et ajustements.
La presente Norme internationale definit un systeme
de tolerances et de surepaisseurs d ’usinage speci-
IS0 1302: 1992, Dessins techniques - Indication des
frees pour les pieces moulees. Elle est applicable aux
&tats de surface.
dimensions des pieces moulees en metal et leurs al-
liages, realisees par les differents procedes de mou-
lage existants [mais voir aussi I’introduction g) et
l’article 51.
La presente Norme internationale est applicable aussi
3 Dbfinitions
bien aux tolerances g&Wales et/au aux surepaisseurs
d ’usinage specifiees donnees sur le dessin qu ’aux
Pour les besoins de la presente Norme internationale,
tolerances individuelles et/au surepaisseurs d ’usinage
les definitions suivantes s ’appliquent.
specifiees, p&i&es 8 la suite d ’une tote particuliere
(voir article 11).
3.1 tote de base: Dimension d ’une piece moulee
brute avant usinage (voir figure 1) comprenant la sur-
Le systeme defini est applicable quand le fondeur
epaisseur d ’usinage necessaire (voir figure 2).
fournit les modeles ou I’outillage ou accepte la res-
ponsabilite de le verifier.
Cotedebasepiece brute
1
2 RbfQrences normatives
Les normes suivantes contiennent des dispositions
qui, par suite de la reference qui en est faite, consti-
tuent des dispositions valables pour la presente
Norme internationale. Au moment de la publication,
les editions indiquees etaient en vigueur. Toute
norme est sujette 8 revision et les parties prenantes
des accords fond& sur la presente Norme internatio-
nale sont invitees a rechercher la possibilite d ’appli-
quer les editions les plus recentes des normes
indiquees ci-apres. Les membres de la CEI et de I’ISO
possedent le registre des Normes internationales en
vigueur a un moment donne.
Figure 1 - Indications de dessin (voir article 4)
1

---------------------- Page: 4 ----------------------
IS0 8062: 1994(F) Q IS0
3.4 variation: Deplacement relatif des surfaces
d ’une piece moulee dQ aux imprecisions des diffe-
rentes parties constituant le moule (voir figure3).
3.5 angle de dkpouille (dbpouille): Pente supple-
mentaire sur les elements de forme (notamment sur
les surfaces enveloppes) necessaire pour faciliter le
demoulage de la piece (du moule, de la coquille ou
du modele) ou la separation des parties d ’un moule
permanent.
4 Cotation
Sauf pour la cotation de 1 ’6paisseur d ’une paroi (qui
peut Qtre definie par une chalne de deux totes), il faut
eviter la cotation en chafne.
Limite maximale de dimension
5 Classes de tokrances
Figure 2 - bimites de tolbrances
II existe 16 classes de tolerances des pieces moulees,
designees CT1 a CT1 6 (voir tableau 1).
Les totes pour lesquelles les tolerances g&Wales ne
3.2 tolbrance dimensionnelle: [Voir IS0 28641.
sont pas appropriees doivent se voir attribuer des to-
3.3 surhpaisseur d ’usinage sp&#ibe, RMA: SW lerances individuelles.
les pieces brutes moulees, surepaisseur de mat&e
En attendant d ’avoir une opinion definitive sur les va-
qui doit permettre de supprimer par usinage ulterieur
leurs des tolerances (dimensionnelles) pour les pieces
les effets de moulage sur la surface, et d ’obtenir ainsi
moulees obtenues par moulage en moule metallique
I’etat de surface desire et la precision dimensionnelle
permanent (gravite et basse pression), par coulee
necessaire.
sous pression et par moulage de precision, d ’autres
Pour les pieces cylindriques ou usinees des deux co- normes de tolerances dimensionnelles plus appro-
tes, la RMA est prise en compte deux fois (voir figu- prices, par exemple des normes nationales, pourront
res 5 et 6). etre utilisees pour ces procedes particuliers.
Variation maximale
Variation maximale
e * a<
s
I
I
I
Variation maximale
I
1 I
I
‘W --
Limite minimdLe de dimension
Limite maximale de dimension
Figure 3 -
Variation maximale
2

---------------------- Page: 5 ----------------------
0 IS0
IS0 8062: 1994tF)
paroi des classes CT1 8 CT1 5 doit &re d ’une unit6
6 Variation
plus 6lev6e que la tol&ance g&Wale pour les autres
totes; par exemple, si la tol&ance g&&ale sur le
Sauf convention contraire, la variation doit se situer
dessin est de CTIO, la tolerance sur Mpaisseur de
dans les limites indiqkes dans le tableau 1 (voir
paroi doit Btre de CT1 1.
figure3). Lorsqu ’il importe de rkduire encore la valeur
de la variation, la valeur maximale doit Btre indiquee
sur le dessin (voir 11 .l ).
8 l%ments de dkpouille
Lorsque le trace requiert un Mment conique (par
exemple un Mment avec un angle de d6pouille), la
7 gpaisseur de paroi
tolhrance doit s ’appliquer symhriquement le long de
la surface (voir figure4).
Sauf convention contraire, la to&rante d ’bpaisseur de
Indication SW Le dessin InterprHation
Cotedebase
Cotedebase
1 1
1
I
Dcipouille +
CT/2
CT/2
e
I
a)
Depouille -
Depouille *
Figure 4 - Zone de tolhrance sur les Mments de dhpouille
3

---------------------- Page: 6 ----------------------
0 IS0
IS0 8062:1994( F)
Toutefois, par accord entre le client et le fondeur pour
Le dessin doit generalement specifier si la depouille
des raisons specifiques, la zone de tolerance peut etre
se compte en plus, en moins, ou en plus et en moins,
asymetrique. Dans ce cas, la tolerance doit etre indi-
par exemple
quee individuellement, a la suite de la tote de base.
depouille +, figure 4 a)
10 Surbpaisseurs d ’usinage spkifihes,
depouille -, figure 4 b)
RMA
depouille +, figure 4 c)
10.1 Gh6ralit6s
Les depouilles des surfaces particulieres, presentees
differemment de la disposition g&Wale des de-
Sauf convention contraire, la surepaisseur d ’usinage
pouilles du dessin, doivent etre indiquees separement
specifiee est valable pour toute la piece brute. On ne
specific done qu ’une seule valeur pour toutes les
4
a la surface, par exemple + .
surfaces a usiner, et celle-ci doit etre choisie dans la
fourchette dimensionnelle appropriee en fonction de
Pour les dimensions usinees, ((depouille +)I s ’appli-
la plus grande dimension hors tout de la piece moulee
quera quelle que soit la specification generale du
finie apres usinage final (voir figure 9).
dessin pour les depouilles, afin que les dimensions
finales puissent Qtre respectees.
La tote maximale d ’un element, brut de coulee, ne
doit pas etre superieure a la tote definitive a laquelle
9 Position de la zone de tokrance
on a ajoute la surepaisseur d ’usinage specifiee et la
tolerance totale de moulage (voir figure 2 et figures 5
Sauf convention contraire, la zone de tolerance doit
.
6 8)
etre repartie symetriquement par rapport a la tote de
Lorsque c ’est le cas, la depouille doit etre consideree
base, c ’est-a-dire une moitie du c&e positif et une
en plus, comme le montre la figure4.
moitie du c&e negatif (voir figure 2).
-
CT/4 CT/4
e --c I-
F RMA
RMA _
I
I
R=F+ZRMA+CT/Z
R = Cote de base de la piece brute
F = Cote de la piece finie
RMA = Surepaisseur d ’usinage specifiee
CT = Tolerance de moulage
Figure 5 - Usinage exthrieur d ’un bossage
4

---------------------- Page: 7 ----------------------
0 IS0
IS0 8062:1994(F)
- -
CT/4
RMA
- ~2:
R=F-ZRMA-CT/Z
Figure 6 - Usinage inthrieur
R=F
(=F-RMA+RMA-CT/4+CT/4)
Figure 7 - Usinage < F RMA
-
R=F+RMA+CT/Z
CT
l-4
Figure 8 - Usinage d ’un c&6 de Wkment
5

---------------------- Page: 8 ----------------------
IS0 8062:1994(F) 0 IS0
b) en cas de restriction concernant la variation (voir
article 4);
EXEMPLE
((Tolkra
...

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