IS 2102-1: General tolerances, Part 1: Tolerances for linear and angular dimensions without individual tolerance indications

8 Pages·1993·1.1 MB·English

by  Bureau of Indian Standards

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IS 2102-1 (1993): General tolerances, Part 1: Tolerances
for linear and angular dimensions without individual
tolerance indications [PGD 20: Engineering Standards]
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IS 2102 ( Part 1 ,) : 1993
IS0 2768-l : 1989

UDC 621’753’1 : 744’4

@ SIB 1993
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IS 2102 ( Part 1) : 1993
IS0 2768-l : 1989
Indian Standard
GENERAL TOLERANCES
PART 1 TOLERANCES FOR LINEAR AND ANGULAR DIMENSIONS WITHOUT
INDIVIDUAL TOLERANCE INDICATIONS
Third Revision )
(
1 Scope 2 General
This part of IS0 2758 is intended to simplify drawing indica- When selecting the tolerance class, the respective customary
tions and it specifies general tolerances for linear and angular workshop accuracy has to be taken into consideration. If smal-
dimensions without individual tolerance indications in four tol- ler tolerances are required or larger tolerances are permissible
erance classes. and more economical for any individual feature, such toleran-
ces should be indicated adjacent to the relevant nominal dimen-
NOTE 1 - The conceptsb ehind the general tolerancingo f linear and sion(s).
angulard imensionsa re describedi n annex A.
General tolerances for .linear and angular dimensions apply
It applies to the dimensions of parts that are produced by metal when drawings or associated specifications refer to this part of
removal or parts that are formed from sheet metal. IS0 2768 in accordance with clauses 4 and 5. If there are gen-
eral tolerances for other processes, as specified in other Inter-
NOTES national Standards, reference shall be made to them on the
drawings or associated specifications. For a dimension
2 These tolerancesm ay be suitablef or use with materialso ther than
between an unfinished and a finished surface, e.g. of cast or
metal.
forged parts, for which no individual tolerance is directly indi-
3 Parallel International Standards exist or are planned, e.g. see cated, the larger of the two general tolerances in question
IS0 60621)f or castings. applies, e.g. for castings, see IS0 806211.
This part of IS0 2758 only applies for the following dimensions
which do not have an individual tolerance indication : 3 Normative references

The following standards contain provisions which, through
a) linear dimensions (e.g. external sizes, int e rnal sizes,
reference in this text, constitute provisions of this part of
step sizes, diameters, radii, distances, external radii and
IS0 2768. At the time of publication, the editions indicated
chamfer heights for broken edges);
were valid. All standards are subject to revision, and parties to
agreements based on this part of IS0 2768 are encouraged to
b) angular dimensions, including angular dimensions
investigate the possibility of applying the most recent editions
usually not indicated, e.g. right angles BOoI, unless ref-
of the standards indicated below. Members of IEC and IS0
erence to IS0 2768-2 is made, or angles of uniform pcly-
maintain registers of currently valid International Standards.
gons;
IS0 2758-Z : .9891 General tolerances - Part 2: Geometrical
cl linear and angular dimensions produced by machining
tolerances for features without individual tolerance indications.
assembled parts.
IS0 8015 : 1985, Technical drawings - Fundamental toleran-
It does not apply for the following dimensions :
cing principle.
a) linear and angular dimensions which are covered by
reference to other standards on general tolerances; 4 General tolerances
b) auxiliary dimensions indicated in brackets; 4.1 Linear dimensions
c) theoretically exact dimensions indicated in rectangular General tolerances for linear dimensions are given in tables 1
frames. and 2.
1) IS0 8062 : 1904, Castings - System of dimensional tolerances.
IS 2102 ( Part 1) : 1993
IS0 2766-l : 1969
4.2 Angular dimensions a) “IS0 2768”;
General tolerances specified in angular units control only the b) the tolerance class in accordance with this part of
general orientation of lines or line elements of surfaces, but not IS0 2768.
their form deviations.
EXAMPLE
The general orientation of the line derived from the actual sur-
face is the orientation of the contacting line of ideal geometrical
IS0 2768-m
form. The maximum distance between the contacting line and
the actual line shall be the least possible value (see IS0 8015).
The permissible deviations of angular dimensions are given in
6 Rejection
table 3.
Unless otherwise stated, workpieces exceeding the general
5 Indications on drawings tolerance shall not lead to automatic rejection provided that the
ability of the workpiece to function is not impaired (see
If general tolerances in accordance with this part of IS0 2768 clause A.4).
shall apply, the following information shall be indicated in or
:
near the title block
Table 1 - Permissible deviations for linear dimensions except for broken edges
(external radii and chamfer heights, see table 2)
Values in millimetres
Permissible deviations for basic size range
Tolerance class 1 1
I n c11 over ) over 1 over 1 over 1 over over 1 over
I
Designation Description
I
6 36 126 400 loo0 2066 46cm
f fine i 0,05 k 0,05 f0.1 kO.15 f 0,2 *0,3 kO.5 -
m medium f0.1 fO,l f 0,2 +0,3 kO.5 f0.8 -L 1,2 *2
C coarse +_0 ,2 + 0.3 +0,5 kO.8 +1,2 f2 +3 +4
V very coarse - f0,5 kl +1,5 f2,5 f4 +6 +_8
1) For nominal sizes below 0.5 mm, the deviations shall be indicated adjacent to the relevant nominal size(s).
Table 2 - Permissible deviations for broken edges (external radii and chamfer heights)
Values in millimetres
Tolerance class Permissible deviations for basic size range
Designation Description 0.5” up to 3 over 3 pu to 6 over 6
/
f fine
---__ I * 0,2 +0,5 fl
m / medium
_~
C coarse
-___.
f 0,4 +1 +2
V very coarse
1)
For nominal sizes below 0,5 mm, the deviations shall be indicated adjacent to the relevant nominal size(s).
Table 3 - Permissible deviations of angular dimensions
Permissible deviations for ranges of lengths, in millimetres,
Tolerance class
of the shorter side of the angle concerned
Designation Description up to 10 over 10 up to 56 over 56 up to 120 over 120 up to 406 over 4lXl
f fine
f10 + 0030’ + 0020 + 0010’ + 005
m medium
C ~____ coar-.s-e -__- It 090 kOO15’ ltOOl0
V very coarse + 30 220 +1o k OY?O’ f 0020’

2
IS 2102 ( Part 1) : 1993
IS0 2768-l : 1989
Annex A
(informative)
Concepts behind general tolerancing of linear and angular dimensions
A.1 General tolerances should be indicated on the drawing c) the drawing readily indicates which feature can be pro-
by reference to this part of IS0 2768 in accordance with duced by normal process capability, which also assists
clause 5. quality engineering by reducing inspection levels;
The values of general tolerances correspond to tolerance d) those dimensions remaining, which have individually in-
classes of customary workshop accuracy, the appropriate dicated tolerances, will, for the most pat-t, be those control-
tolerance class being selected and indicated on the drawing ac- ling features for which the function requires relatively small
cording to the requirement for the components. tolerances and which therefore may require special effort in
the production - this will be helpful for production plan-
ning and will assist quality control services in their analysis
A.2 Above certain tolerance values, there is usually no gain of inspection requirements;
in manufacturing economy by enlarging the tolerance. For
example, a feature having a 35 mm diameter could be manufac- e) purchase and sub-contract supply engineers can
tured to a high level of conformance in a workshop with negotiate orders more readily since the “customary
“customary medium accuracy”. Specifying a tolerance of workshop accuracy” is known before the contract is placed;
k 1 mm would be of no benefit in this particular workshop, as this also avoids arguments on delivery between the buyer
the general tolerance values of *0,3 mm would be quite and the supplier, since in this respect the drawing is com-
adequate. plete.
However, if, for functional reasons, a feature requires a smaller These advantages are fully obtained only when there is
tolerance value than the “general tolerances”, then that feature sufficient reliability that the general tolerances will not be
should have the smaller tolerance indicated individually adja- exceeded, i.e.’ when the customary workshop accuracy of the
cent to the dimension defining its size or angle. This type of particular workshop is equal to or finer than the general
tolerance falls outside the scope of general tolerances. tolerances indicated in the drawing.
In cases where the function of a feature allows a tolerance
The workshop should, therefore
equal to or larger than the general tolerance values, these
should not be indicated adjacent to the dimension but should - find out by measurements what its customary
be stated on the drawing as described in clause 5. This type of workshop accuracy is;
tolerance allows full use of the concept of general tolerancing.
- accept only those drawings having general tolerances
There will be “exceptions to the rule” where the funct i on of the equal to or greater than its customary workshop accuracy;
feature allows a larger tolerance than the general tolerances,
and the larger tolerance will provide manufacturing economy. - check by sampling that its customary workshop accu-
In these special cases, the larger tolerance should be indicated racy does not deteriorate.
individually adjacent to the dimension for the particular feature,
e.g. the depth of blind holes drilled at assembly. Relying on undefined “good workmanship” with all its uncer-
tainties and misunderstandings is no longer necessary with the
concept of general geometrical tolerances. The general
A.3 Using general tolerances leads to the following advan- geometrical tolerances define the required accuracy of “good
tages : workmanship”.
a) drawings are easier to read and thus communication is
4.A
made more effective to the user of the drawing; The tolerance the function allows is often greater than
the general tolerance. The function of the part is, therefore, not
b) the design draughtsman saves time by avoiding de- always impaired when the general tolerance is ioccasiorlallv)
tailed tolerance calculations as it is sufficient only to know exceeded at any feature of the workpiece. Exceeding the
that the function allows a tolerance greater than or equal to general tolerance should lead to a rejection of the workpiece
the general tolerance; only if the function is impaired.

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