CHECKS AND MEASUREMENTS
Memo
ISO - GPS Specification
GD & T
CA
R
Edition 2018
NO
T
Foreword
CONTENTS - Memo ISO-GPS Specification GD & T
Generalities
In order to ensure continuous improvements to industrial
products and help to establish a general and rigourous
communications system for industrial operators, the standardisation way framework relating to the “Geometric
Product Specifications” (GPS) aims to provide increasingly
advanced tools of expressing functional requirements
in a more and more effective manner, and to share the
results of the verification processes.
The GPS system provides a means of communication
whereby designers, production engineers, qualitician,
inspectors and metrologists can exchange information
on the allowable geometries of manufactured parts
it is done on the basis of specifications (dimensional,
geometric and surface texture) indicated on a drawing
and/or an associated technical document. The associated
graphic and symbolic “language” uses the syntax and
semantics defined in GPS standards.
National, European and international standards in
the field are prepared and applied by National standardisation committees: ; these committees establish National
positions for international (ISO/TC213) and European
(CEN/TC 290 with UNM secretariat) works.
Participation in standardization works allows operators
to plan ahead for changes to standards and influence
their content, rather than just following instructions.
Managed by UNM in France, BSI in UK, DIN in Germany,
DS in danemark, SAS in Sweden, …
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Conformity
Principles behind the declaration of conformity (unless a specific
customer / supplier agreement applies) ISO 14253-1
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Dimensional specification ISO 14405
Linear dimensional specifications
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Angular dimensional specifications
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Geometrical specifications
Introduction ISO 1101:2017
Generality and toleranced features
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Tolerance zone
32
Geometrical specifications
Datums ISO 5459: 2011
Geometrical tolerance indicator: ISO 1101
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Datums and datum system
36
Datum system and common datums
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Restricted datums and datum targets
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Examples and meaning (second part)
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Generalities
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Why do we need GPS?
Geometrical product specifications (GPS) can be used to describe the authorised
limits of deviations for the characteristics of a surface texture, dimension,
form, orientation and/or location, which can be observed on products. They are
defined by drawing indication.
Surface
Cartesian system
From a nominal point of view:
– a cylinder has a size: its diameter - it is a feature of size (2D or 3D);
– a cylinder has no length (independently to the two limiting planes)
and represents a cylindrical surface.
Translation along its axis (z) or the rotation around the axis (w) cannot
be blocked - they are the invariance degrees of the cylinder.
The following can be limited:
– o ne or two translations defined as perpendicular to the axis
of the cylinder;
– a nd/or one or two rotations defined around axes which
are perpendicular to the axis of the cylinder;
– form deviations;
– and/or surface texture parameters;
– and/or dimensional deviations.
Part Ro
Cartesian system
…as the real feature will be imperfect.
Note: Degrees of freedom are given in reference (x, y, z) relating to the surface and not the
CAD (x0 ,y0, z0) used to draw the part; but from a real point of view, these degrees of Cartesian
systems relate to a datum or a datum system.
Important: do not mix up datums and cartesian systems (cf. ISO 5459)
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Generalities
Default principles (no specific indications)
ISO 8015 (principle of amended feature)
Independency principe
Rigidity principle
Each GPS (dimensional, geometrical and surface texture) must be individually
satisfied (independently from the other GPS) unless indicated to the contrary.
By default, a part is considered as rigid and insensitive to external factors
(gravity, assembly force, etc.), unless standard ISO 10579 - NR is referred to.
Definition principle
Reference condition Principle
Requirements which are not specified on the drawing cannot be mandatory
(referred to). Only the general and individual GPS specification are mandatory.
By default, all GPS apply to the reference conditions. By default, this refers
to the normal reference temperature defined as 20 °C (standard ISO 1) and
the total absence of contaminating features. All other applicable conditions
must be defined on the drawing (e.g.: hygrometry).
Feature principle
A part must be considered as comprising a given number of simple limited
features, generally based on “natural“ borders.
By default, all GPS specification relating to a feature or a relationship between
features apply to the complete feature (or) ; and each GPS specification only
applies to one single feature or one single relationship between features. The
United Feature (UF) unifies different portions they can be considered together
as a single feature.
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Responsibility principle
a) The correlation between the function, the specification and specification
uncertainty (interpretability) is the responsibility of the party who defined the
specifications (Customer) related to the intended function.
b) Unless specifically agreed otherwise, measuring uncertainty is the responsibility of the party providing proof of conformity or non-conformity with specifications (see ISO 14253-1). Measuring uncertainty quantifies the accuracy
of the agreement between the verification operator and the specification
operator (cf. ISO 17450-2).
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GPS specifications are requirements describing a condition (upper specification
limit USL and/or lower specification limit LSL) applicable to characteristics
(geometrical, dimensional or surface texture), and translated into a symbolic
language on the drawing in order to express:
Generalities
GPS specification
Generalities - ISO 17450 -1
Ideal representation of the part
without imperfections: nominal
model
LSL ≤ Characteristic ≤ USL
or
LSL ≤ Characteristic
or
Characteristic ≤ USL
A condition can apply:
– to a specific dimension or geometrical feature - individual tolerance.
or
– to all geometrical features or dimensions, with the exception of those
affected by individual tolerances - general tolerance, e.g. by indicating
ISO 2768-mK*.
GPS specifications are indicated in link with the nominal model (on the definition
drawing or on the specification digital mockup specified).
Representation exagerating the
imperfections on the workpiece
Each characteristic is defined using a set of geometrical operations, considering
both the nominal model (ideal expectation) and the actual produced geometry
of the obtained workpiece.
* General tolerancing standard for machined parts: the first lower case letter indicates a level
of dimensional tolerances and the second upper case letter indicates the level of geometrical
tolerances.
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The meaning of the GPS, and therefore the definition of the characteristic,
is associated with the manufactured part (represented using a non-ideal model
of the part, also known as a “skin model“).
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Generalities
Geometrical feature
ISO 17450 -1
By considering the feature principle (ISO 8015), it is important to consider
a different relationship with the feature (this is a geometrical entity and not
a technological entity) and to not mix up the ideal view (nominal feature)
with reality, from with the GPS process is done.
Extracted integral feature
Plane 1
Cylinder 1
Plane 2
Cylinder 2
Extracted derived feature
Plane 3
3D Representation of the real workpiece (skin model)
with exaggerated imperfections
Nominal 3D model
of the part
Extracted integral feature
Extracted derived feature
2D Representation of the real workpiece (skin model)
with exaggerated imperfections
2D Nominal model
of the part
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Generalities
Geometrical feature
ISO 17450 -1
1 – Different point of views must be taken into consideration in
the specification and verification process, introducing specific
qualifiers, to complement the word “feature”.
Nominal
Real
Extracted
Associated
Feature represented
in the drawing
workpiece
Observed feature
Ideal feature – established
from the real workpiece or
the extracted feature
Integral
feature
Feature
Derived
feature
2 – It can be useful for a given feature to distinguish (e.g. a cylinder):
- its median feature (eg its axis) as known as its skeleton or derived feature and
- its skin (e.g. its surface) as known as integral feature.
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Generalities
Integration of the complete or restricted
feature ISO 1101 / ISO 14405 -1
By default, dimensional, geometrical
or surface texture characteristics
must be evaluated for the complete
feature considered.
When a restriction of the
feature must be considered,
then it shall be indicated,
for example as follows.
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Generalities
Three families of GPS specifications
ISO 14405 / ISO 1101 / ISO 1302 & 25178-1
Family
Example of indications
Illustration
Dimensional specifications
(see ISO 14405)
The characteristic observed is a size.
FILTERING
Surface texture specifications
(see ISO 1302
for 2D et 25178-1 for 3D)
The characteristic observed depends on deviations detected between
a part of the geometrical feature to which one or more filters have been applied
and a theoretical feature.
Geometrical specifications
(see ISO 1101)
The observed characteristic is a “deviation” between a geometrical feature
related to the real workpiece and one perfect feature using the nominal
property of the part.
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Principles behind the declaration of conformity
(unless a specific customer / supplier agreement
applies) ISO 14253-1
USL
LSL
USL
DECLARATION OF CONFORMITY
By default, the conformity is declared by the party delivering the manufactured
product, which is responsible for estimating measurement uncertainty.
Conformity
Ideal view: check all parts and zero measurement
uncertainty
LSL
View 1
View 2
LSL
USL
U*
U*
U*
U*
LSL
USL
To declare conformity, the result:
– with uncertainty, mustLSL
be within the specificationUSL
limits (view 1);
– without uncertainty, must be within a restricted zone with reference
to specification limits (view 2).
*Factoring in a 5% risk of taking the wrong decision.
LSL: lower specification limit
USL: upper specification limit
Note: A measurement result (R) should always be defined with its measurement
uncertainty: R ± U
DECLARATION OF NON-CONFORMITY
By default, the non-conformity is declared by the party receiving the manufactured
product, which is responsible for estimating measurement uncertainty.
Keys
U*
View 1
U*
Zone considered as:
LSL
Conform
USL
View 2
Non-conform
Uncertain zone
to be considered as:
Observed Result (with
or without measurement
uncertainty)
U*
Conform
Non-conform
R without U
R with ± U
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U*
U*
U*
U*
U*
LSL
USL
LSL
USL
To declare non-conformity, the result:
– with uncertainty, must be outside of the specification limits (view 1);
– without uncertainty, must be within an extended zone with reference
to the specification limits (view 2).
*Factoring in a 5% risk of taking the wrong decision.
If the application of the principle of declaring conformity and nonconformity is not mandatory, the replacement rule must be defined
between customer and supplier.
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Linear dimensional
specifications ISO 14405-1
Linear
A Linear dimensional specification only applies to a feature of size
(e.g.: diameter of a cylinder, distance between two parallel opposed planes,
diameter of a sphere).
The construction of local dimensions of type “two points size” is defined in ISO 17450-3.
Modifiers can be used to modify
the characteristic(s) to be evaluate
For this indication with the envelope requirement, it is important to check
that all local two points sizes are observed within the interval [9.9; 10.1]
and that the outer material envelope defined by a perfect cylinder with the
maximum material diameter (10.1) is not exceeded (i.e. that the part must
fit in a “GO“ gauge).
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Dimensional
Unless a specific general indication or individual indication exists, a linear
dimensional specification exclusively applies to the local two points size of
a geometrical feature.
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Linear dimensional
specifications ISO 14405-1
Examples of modifiers defining various size characteristics
for a considered feature
LP
LS
Dimensional
GG
GX
GN
8SA
6
SN
Value
LP
LP
LP
Local
Two points size (1)
LP
LP
LP
LS
LS
LS Local sphere size (1’)
LS
LS
LS
GG
GG
GG
GG
Least square/Gaussian (2)
GG
GG
GX
Global
GX
GX Maximum inscribed (3)
(section, portion,
GX
GX
complete)
GX
GN
GN Minimum circumscribed (4)
GN
GN
GN
GC
GN
SA Minimax/Chebitchev (5)
SA
SA
SA Average value (6)
SD
SA
SN
Statistics
SN
Minimum value (7)
GC
SN
GC
GC
SN
SM
SN
SX Maximum value (8)
SX
SD
SX
SD
SD
SX Mid-range Value
SQ
SX
SR
SR
Median value (X50%)
SM
SR
SM
SM
SR Range of values (9)
SR
SQ
SQ
SQ Standard deviation of values
0,2 GN
GN ACS
ACS SR
SR
0,2
0,2 GN ACS SR
0,2 GN
ACS
SR
GN
ACS
SR
Other indications can0,2
be used
0,2
GNto define
ACSrestrictions
SR applicable to a fixed
SX
9
SR
No. of local size
0,2 GN ACS SR
or sliding zone: ALS (any longiditunal section), ACS (any cross section),
“/XXX“ (over a slided restricted length), SCS (specific cross section), etc.
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Linear dimensional specifications
ISO 14405 -1 & 2
Examples of modifiers defining various size characteristics
for a considered feature.
The diameter of the minimum circumscribed cylinder shall be less than 10.2
and the diameter of the maximum inscribed shall be more than 9.9.
Dimensional
All two points sizes must be between 9.8 and 10.2 and their range
must be less than 0.15.
The common minimum circumscribed diameter to both cylindrical surfaces must
be less than 10.1 and all two points size diameters must be upper than 9.9.
The diameter of the minimum circumscribed circle in a specific cross section
2 mm from the upper face must be between 9.9 and 10.1 (SCS precises that
the theoretical exact dimension 2 mm applies to the dimensional specifications).
The diameter of the maximum inscribed cylinder of the borehole shall be between
9.9 mm and 10.1 mm, the diameter of the minimum circumscribed cylinder shall be
equal to 13 mm and the range of the local thickness defined between two points
at any position and defined in any logitudinal symmetry plane passing through the
specified reference B (“axis” of the borehole) shall be at least equal to 0.1 mm.
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Angular dimensional
specifications ISO 14405-3
Angular dimensional specifications only apply to a dimensional entity/feature
with an angular size (example: angle of a cone, angle of a prism).
The angular dimensional characteristics by default corresponding to application
of modifier
.
Dimensional
Characteristic: local angle (1) between two co-planar lines (2).
These straight lines are associated with minmax objective function (chebitchev)
and constrained external material tangents material outer tangents to the
integral extracted lines (3) defined by the intersection between the integral
surfaces and a plane (intersecting) (4) passing through the axis (5)
of the associated cylinder (6) (maximum inner diameter at the inner hole).
Characteristic: local angle (1) between two co-planar lines (2).
These straight lines are associated with minmax objective function and
constrained external material tangents material outer tangents to the integral
extracted lines (3) defined by the intersection between the integral surfaces
and a plane (4) (implicitly intersecting) perpendicular to the intersection straight
line (5) for the two associated planes (6) (with the least square criterion).
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Angular dimensional specification:
modifiers: ISO 14405 -3
Statistical
0,2
0,2
0,2
0,2
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8
6
7
9
Number of global angular size
Other additional indications can be used
(example: CT, SCS, A ↔ B) modifying the meaning
of the specification.
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Dimensional
Global
(section, portion,
complete)
3: intersecting plane
Value
Local
LP
LP
LP
LC
LP
LS
LC Two-point size (1)
LC
LS
LS
Local sphere size (1’)
LG
LS
GG
LG
LG
GG
GG
GG
GG
GX
GG
GG Least square / gaussian (4)
GX
GX
GC
GX
GN
GC Minimax / Chebitchev (5)
GC
GN
GN
SA
GN
SA
SA
SA
SA
SA
SN Average value (6)
SA
SN
GC
GC
SN
SN Minimum value (7)
SN
GC
SN
SX Maximum value (8)
SN
SX
SD
SD
SX
SX Mid-range Value
SX
SD
SX
SD Median value (X50%)
SX
SR
SM
SM
SD
SD Range of values (9)
SR
SM
SR
SM
SR
SQ
SQ
SM Standard deviation of values
SM
SQ
GN SR
ACS SR
SR
SR
GN
GN ACS
ACS SR
SR
SQ
GN SQ
ACS SR
SQ
0,1
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Generality
Toleranced features
A geometrical specification defined a tolerance zone representing a portion of
the space bounded perfect geometry, which must contain the toleranced feature,
to define conformity. The tolerance zone can be constrained in terms of orientation,
and location from datums. The datums are established from datum features.
It can also be expressed as a condition (tolerance) on a characteristic established
between geometric features: the toleranced feature and the reference feature
(median feature of the tolerance zone).
Indication of the requirement
Real workpiece
0,1
Meaning
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1
2
3
1 – Toleranced feature
5 – Reference feature
2 – Datum feature
6 – Local geometric deviation
3 – Datum
7 – Observed characteristic
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7
5
1
2
4 – Tolerance zone
3
Characteristics & condition
2.Max(|di|) ≤ 0,1
Tolerance zone
the extracted integral feature
corresponding to the designated
nominal feature
The toleranced
feature is
➋ Leader line aligned
with a dimension line
Workpiece
the extracted derived feature
(“extracted axis”)
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Introduction ISO 1101:2017
➊ Leader line not aligned
with a dimension line
Geometrical specifications
The type of toleranced feature (derived or integral) depends
on the position of the leader line compared to dimension line.
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Tolerance zone
Unless specifically indicated otherwise, the median feature of the tolerance
zone has the nominal shape of the toleranced feature. The geometry of
the tolerance zone is defined as the space limited by two lines or surfaces
equidistant from the median feature, where the distance between the two
lines or surfaces is equal to the tolerance value.
1 – Median feature (of 3)
2 – Equidistant features (from 1)
3 – Tolerance zone (bounded by 2)
Datums
Constraint of
the tolerance zone
No
No
Yes
Orientation (angle)
Yes
Orientation and location
(angle + distance)
Form symbol
Orientation symbol
If the symbol ∅ or S∅ precedes the tolerance value in the second compartment of the tolerance frame, then the tolerance zone corresponds to the space
within a cylinder or a sphere respectively, with a diameter corresponding to
the tolerance value.
1 – Median feature
2 – Tolerance zone
The orientation and location of the tolerance zone may be constrained by
datums (the type of constraints depending on the symbol of the characteristic).
If the toleranced feature is an “extracted axis” (which is nominally straight),
and if the symbol ∅ does not appear in front of the tolerance value,
the tolerance zone corresponds to the space between two opposite parallel
planes for the tolerance. In this case, the width of the tolerance zone is in
the direction of the leader line (the degrees of freedom for orientation are
not constrained by the datum(s)).
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*No datum required for a pattern of n features, but indicated with CZ or CZR
else with CZ or CZR or SZ when the datum system does not lock all degrees of
freedom of tolerance zones.
Run-out symbol
Orientation or location
(angle / distance)
Yes
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Introduction ISO 1101:2017
*
Geometrical specifications
Location symbol
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Geometrical tolerance indicator:
ISO 1101
A geometrical specification is expressed on the diagram with a tolerance
indicator, a, (tolerance frame) and a leader line, b, designating a geometrical
feature from which the toleranced feature shall be extracted.
The tolerance indicator can be supplemented by adjacent indications in zone
C, (indicate, for example: 2x or A ↔ B), and in zone D, to provide indications
using an intersection plane, orientation plane, collection plane or direction
feature indicators, or the SIMi indicator, for simultaneous requirements (since i
is an optional number).
The tolerance indicator is broken down from left to right in two
to three sections:
- The symbol section (a1) presenting the geometrical characteristics
- The zone section, specificity of the feature and the characteristic (a2)
C
- The datum section (a3) describing the datum system(s) if required
G
Section a2 can present multiple possible modifiers,
as presented below
Shape
Width and
range
Comb.
Specified offset
Toleranced
Constraint
Associated
feature
Filter
Type
feature
Nesting
index
0,05
∅
S∅
0.02-0.05
0.05/75x30°
CZ
SZ
UZ+0.2
UZ+0.2:-0.3
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OZ
G
C
G
C
Association
X
N
N
T
A
X
X
Material
Constraint
condition
state
Characteristic
G
Derived
N
feature
G
G
Parameter
T
T
P
A
A
M
P
P
L
F
G
NX
Objective
function
NX T
C
XT A
G
E
P
M
M
I
V
L
L
0.8
C
C
C
G
G
G
TA P
X
N
VA
S
-250
><
…
0.8-250
N
N
N
AP 27
M
…
X
X
X
P 32-5
ML
T
T
T
ML
A
A
A
LF
Constraint
T
Q
F
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F
F
Datums ISO 5459: 2011
Tolerance zone
C
feature and characteristic
N
Geometrical specifications
A few modifiers in section a2, zone,
C
C
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Datums and datum system
A datum is established from a datum feature (1), identified on the drawing
with an indicator triangle:
– attached to a dimension line (directly or indirectly), if the feature is a feature
of size (e.g.: datum feature C and F);
– not attached to a dimension line, if the feature is not a feature of size (e.g.: A,
B or E).
An ideal feature (2) (associated feature)
will be fitted to this datum feature with or
without constraints. To define the datum,
only situation features (4) for the associated feature will be retained, i.e. a
collection comprising a plane (PL), and /or a straight line (SL) and /or a point
(PT) allowing to locate and orientate an ideal feature in space.
If a datum consists of at least two situation features (point, straight line, and/or
plane), then it is possible to only use one or two from the list, using the modifiers
([PL], [SL] or [PT]).
These datums are used to constrain the orientation or the location of the tolerance
zone, or even define other features such as intersection or orientation planes.
a)
b)
The indicator triangle D indicates the datum feature (1).
The primary datum D corresponds to the set (4) of a straight line [SL] and a point
[PT]. The primary datum D followed by [SL] only corresponds to the straight line.
1: datum feature
2: associated feature
A datum locks all degrees of freedom it can constrain (orientation and position:
angle and distance). The modifier >< shall be indicated to constrain only the
orientations and let free the possible location constraints.
3: gauge plane
4: datum (D)
5: datum (B)
B ><
6: tolerance zone of specification b)
B
Common datum
B-C
Datum system
B C
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For specification a), it shall use the gauge plane (3) ([SL]+[PT] of D are considered).
For specification b), it shall not to use the gauge plane (3) (only [SL] of D is considered).
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Datums ISO 5459: 2011
Single datum
Geometrical specifications
The datums are identified by the tolerance frame via:
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Datum system
and common datums
A common datum (e.g.: B-C) is established
from at least 2 datum features without an
order of priority in the order of association
(simultaneous associations), with orientation
and location constraints between the
associated features.
A datum system is defined by an ordered collection of single or common datums,
defining a priority in the association (introducing orientation constraints only for
the following datums) in the order defined in the tolerance frame.
The feature associated with the secondary datum feature is only constrained
in terms of orientation from the primary datum. The tertiary datum will also be
constrained by the primary and then the secondary datum.
Association constraints relating to the size
of an associated feature or orientation and location constraints between
situation features of associated features depend on the indications
of the tolerance frame.
Association constraints relating to the size of an associated feature or orientation and location constraints between situation features of associated features
depend on the indications given in the tolerance frame.
Median plane
Intersecting straight line
Primary plane
Intersecting straight line
(1) tangent plane associated with the real surface;
(2) associated tangent plane constrained to 90° compared to 1;
(4) tangent planes simultaneously associated with an orientation constrained at 90°;
(3) associated cylinder, with its axis constrained to be parallel to 1.
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C B
B A
Primary plane
Intersecting straight line
Primary plane
Projection of the cylinder axis
The above examples define the common datums or datum system as a collection
of a plane [PL] (5) and a straight line [SL] (6).
A common datum or a datum system corresponds to the collection of situation features
which cannot lead to the maximum to a set of a plane [PL], a straight line [SL], and a point [PT].
In these examples, this set is a plane (5) and a straight line (6).
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Datums ISO 5459: 2011
B C
Geometrical specifications
B-C
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Restricted datums features
and partial datum targets
If the datum feature is only partially considered, then a restriction must
be defined:
– directly on the surface, or
– via datum targets, or
– moveable datum target (in the direction of the mobility indicator).
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Datums ISO 5459: 2011
Note: The interface between the contact feature (CF) and the part gives datum targets datums
which are nominally portions of surfaces, lines or points. The modifier [DV] can be used to
release the fixed distance used by default to establish a common datum.
Geometrical specifications
The datums are defined by associating a feature with perfect shape (associated
feature), which has the nominal geometry of the datum feature by default, unless
the modifier [CF] is used, in which case the geometry is described on the drawing.
CHECKS AND MEASUREMENTS
Memo
Examples and meaning
CA
R
Edition 2018
NO
T
CONTENTS - Examples and meaning
Types of geometrical specifications
REMINDER
“Constraint”
The term “constraint” is used if a feature
is associated for orientation or positioning
purposes. The notion of requirement will sometimes be used instead of constraint
to simplify understanding.
Straightness
4
Flatness
6
Roundness
8
Cylindricity
10
Profile of line
12
Profile of surface
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Profile of line – profile of surface constrained in orientation only 16
CZ/SZ
Parallelism – Perpendicularity – Angularity
Position
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Position with
CZ or SZ
Coaxiality – Concentricity
The standard refers to an “offset profile”, considering that the offset is applied at every point
of the feature considered, depending
on the direction of the normal vectors.
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Symmetry
“Offset profile”
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with CZ/SZ
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Circular run-out
28
Total run-out
30
Modifiers
Maximum material – Least material – Reciprocity
32
Free state (of restrained
condition)
A
36
Projected tolerance
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AM L R
M L RF
F ACZ
P
P
A
, Combined
zone
,
C
CZ CUZ
A
A
VA
, Modifier
A
C
Collection
plane
C
a
b
C
A
+a
A
PPP
CZR
and SIM
, Modifier
P
SZ/CZ/CZR
, Sequence
b
B
P
P
a
b
Undefined aedge
+
b
b
Edge of undefined shape
42
44
Intersection plane – Orientation plane
A
B
C
+a
40
UZ Czone – Offset zone
, Asymmetric
C
AAA
A
MMMLL LRRR
M L R
FFF
F
CZ
CZ
A CZ
CZ
UZ
L UZ
RUZ
M A
46
48
50
52
UZ
L R
M F
F
CZ
CZ
UZ
UZ
54
Glossary
56
+a
Memob ISO-GPS Specification GD & T (first part)
3
BACK TO CONTENTS
Type of geometrical
specifications
MEANING
EXAMPLE
ISO
1101: 2017
1
2
GEOMETRICAL
CHARACTERISTIC
Symbol:
Straightness
3
TYPE SPECIFICATIONS
5
4
Toleranced feature (1: integral feature):
any extracted integral line, intersection between the real specified surface (3)
and a plane (4) passing through the axis (5) of the associated feature.
Tolerance zone (2): Space between two parallel straight lines
at a distance of 0.3 mm and co-planar to the intersection plane (4),
and adjusting to the toleranced feature with no external constraint.
TOLERANCED FEATURE
Integral (line)
Derived (line)
USABLE
MODIFIER
1
2
3
EXAMPLES OF COMPLEMENTARY INDICATIONS
A
M L
R
F
CZ
UZ
Toleranced feature (1: derived feature):
Extracted axis (1) of the real specified surface (3).
Tolerance zone (2): Space within a cylinder with a diameter of 0.2 mm
and adjusting to the toleranced feature with no external constraint.
A
4
M L
R
5
BACK TO CONTENTS
EXAMPLE
MEANING
Type of geometrical
specifications
ISO
1101: 2017
GEOMETRICAL
CHARACTERISTIC
Symbol:
Flatness
TYPE SPECIFICATIONS
The toleranced feature is the portion (3) of the extracted integral surface (1)
defined by the intersection with a cylinder (2) with a radius 9 mm.
The tolerance zone is the space between two parallel planes at a distance of
0.03 mm, with no external constraint (no datum).
TOLERANCED FEATURE
Integral (surface)
Derived (surface)
USABLE
MODIFIER
EXAMPLES OF COMPLEMENTARY INDICATIONS
A
A
M
M LL R
R
FF
CZ
CZ
UZ
UZ
The toleranced feature is the extracted integral surface at the base
of the counterbore (2).
The tolerance zone is the space between two parallel planes at a distance
of 0.03 mm (1), with no external constraint (no datum).
A
6
M L
F
R
7
BACK TO CONTENTS
EXAMPLE
MEANING
Type of geometrical
specifications
ISO
1101: 2017
GEOMETRICAL
CHARACTERISTIC
Symbol:
Roundness
TYPE SPECIFICATIONS
TOLERANCED FEATURE
Integral (line)
Derived
In the case of non-cylindrical or spherical revolute
surfaces, the direction feature shall be indicated
USABLE
MODIFIER
EXAMPLES OF COMPLEMENTARY INDICATIONS
The toleranced feature (1) is any extracted integral line corresponding
to the intersection between the extracted integral surface (3) and a plane (4)
perpendicular to the axis of the associated cone (5).
The tolerance zone (2) is the space between two co-planar and concentric
circles at a distance of 0.05 mm (the diameter varies for each section).
A
A
M
M LL R
R
FF
CZ
CZ
UZ
UZ
In the case of a cylindrical and spherical surface, the
direction feature shall not be indicated.
A
8
M L
R
9
BACK TO CONTENTS
MEANING
The toleranced feature (1) is a defined portion of complete extracted
integral surface starting 8 mm from the collar, on an extend of 80 mm.
The tolerance zone (2) is the space between two portions of co-axial
cylinders at a radial distance of 0.05 mm and with a length of 20 mm
moving along the toleranced feature, and adjusted to this feature
with no external constraint.
GEOMETRICAL
CHARACTERISTIC
Symbol:
Cylindricity
TYPE SPECIFICATIONS
TOLERANCED FEATURE
Integral (surface)
Derived
USABLE
MODIFIER
The toleranced feature (1) is the complete extracted integral surface.
EXAMPLES OF COMPLEMENTARY INDICATIONS
A
A
M
M LL R
R
FF
CZ
CZ
UZ
UZ
The tolerance zone (2) is the space between two co-axial cylinders
at a radial distance of 0.05 mm and adjusted to the toleranced feature
with no external constraint.
A
10
M L
R
11
Type of geometrical
specifications
EXAMPLE
ISO
1101: 2017
BACK TO CONTENTS
EXAMPLE
MEANING
Type of geometrical
specifications
ISO
1101: 2017
GEOMETRICAL
CHARACTERISTIC
Symbol:
Profile of line
The toleranced feature (1) is any extracted integral line partitionned from
the outline (unified feature of the outline).
The tolerance zone (2) corresponds to the space between two co-planar
profile lines (3) at a distance of 0.04 defined as equidistant from a feature
with the same dimensions as the nominal profile line (4), whose dimensions
have been defined by the theoretical exact dimensions.
TYPE SPECIFICATIONS
TOLERANCED FEATURE
Integral line
Derived line
USABLE
MODIFIER
EXAMPLES OF COMPLEMENTARY INDICATIONS
A
M L
R
F
Note: the theoretical exact dimensions are given
CZof the model).
by the CAD model (digital make-up
UZ
12
The toleranced feature (1) is any extracted integral line considered
in any intersection plane (5) parallel to the specified datum plane C.
The tolerance zone (2) corresponds to the space between two co-planar
profile lines (3) (intersection plane) at a distance of 0.06 defined as
equidistant from a feature with the same dimensions as the nominal profile
line (4), according to the digital definition of the model.
13
A
BACK TO CONTENTS
EXAMPLE
MEANING
Type of geometrical
specifications
ISO
1101: 2017
GEOMETRICAL
CHARACTERISTIC
Symbol:
Profile of surface
TYPE SPECIFICATIONS
The toleranced feature (1) is the extracted integral surface.
The tolerance zone (2) is the space between two cones (3) at a distance of
0.04 defined as equidistant from the nominal surface profile (4) (30° cone
angle), which is constrained with reference to the datum system (B/A);
i.e. the zone axis must be perpendicular to the datum plane B and co-axial
to the datum A (constrained itself perpendicular to datum B).
TOLERANCED FEATURE
Integral surface
Derived surface
USABLE
MODIFIER
EXAMPLES OF COMPLEMENTARY INDICATIONS
A
M L
F
CZ
UZ
14
R
The toleranced feature (1) is the extracted integral surface.
The tolerance zone (2) corresponds to the space between two profile surfaces
(3) at a distance of 0.05 defined as equidistant from a feature with the same
dimensions as the nominal profile surface (a sphere with a diameter of 20
in this case).
15
A
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3
GEOMETRICAL
CHARACTERISTICS
Type of geometrical
specifications
MEANING
EXAMPLE
ISO
1101: 2017
2
Symbols:
Profile of line
1
4
5
Profile of surface
The toleranced feature (1) is any extracted integral line from the outline
(unified feature of outline).
The tolerance zone (2) is the space between two co-planar profile lines (3)
at a distance of 0.04 defined as equidistant from a feature with the nominal
shape (sized to the theoretical exact dimensions), constrained only orientated
at an angle of 105° from datum M (5).
TYPE SPECIFICATIONS
TOLERANCED FEATURE
Integral
Derived
1
2
USABLE
MODIFIER
5
4
EXAMPLES OF COMPLEMENTARY INDICATIONS
A
A
M
M LL R
R
FF
CZ
CZ
UZ
UZ
16
A
3
The toleranced feature (1) is the extracted integral surface.
The tolerance zone (2) is the space between two cones (3) at a distance
of 0.04 defined as equidistant from the nominal surface profile (4) (30° cone
angle), which must be only constrained orientated perpendicular to the single
datum B (5).
17
BACK TO CONTENTS
Type of geometrical
specifications
MEANING
EXAMPLE
ISO
1101: 2017
GEOMETRICAL
CHARACTERISTICS
Symbols:
Parallelism
Perpendicularity
a)
Angularity
TYPE SPECIFICATIONS
c)
TOLERANCED FEATURE
Integral
Derived
b)
(nominally a plane
or straight line)
The toleranced feature is for:
– a) the extracted integral surface (of the inclined face): 1a;
– b) the extracted integral surface (of the rear face): 1b;
– c) the extracted derived feature (extracted axis of the hole,
see ISO 17450-3): 1c.
USABLE
MODIFIER
EXAMPLES OF COMPLEMENTARY INDICATIONS
A
M L
F
CZ
UZ
18
R
The tolerance zone is the space included in for:
– a) and b) between planes at a distance of 0.3 mm (3a)
and 0.1 mm (3b) respectively;
– c) a cylinder with a diameter of 0.2 mm (3c);
which must be:
– a) at an angle of 115°
– b) parallel
– c) perpendicular
at the single datum A (2) (material external tangent plan).
19
BACK TO CONTENTS
MEANING
EXAMPLE
Type of geometrical
specifications
ISO
1101: 2017
GEOMETRICAL
CHARACTERISTIC
Symbol:
a)
Position
TYPE SPECIFICATIONS
The toleranced feature (1) is the extracted integral feature
(1a: side face, 1b: bottom face).
“The” tolerance zone is the space between the 2 parallel planes
at a distance of:
- a): 0.4 mm (3a);
- b): 0.1 mm (3b).
whose median feature must be:
- a): located at 42 mm from the datum A (2);
- b): constrained, from the A/B/C datum system, perpendicular to A and C
and at a distance of 30 mm from the specified datum B (2’) which must be
constrained perpendicular to the datum A.
b)
TOLERANCED FEATURE
Integral
Derived
USABLE
MODIFIER
B
18
A
EXAMPLES OF COMPLEMENTARY INDICATIONS
25 ±0,07 E
R12,5
A
M L
R
F 2,5
12 H12
CZ
a)
0,2 A
UZ
0,6 A B b)
The toleranced feature is the extracted axis of the hole (see ISO 17450-3).
The tolerance zone (1) is the space in a cylinder with a diameter of 0.2 for a)
and 0.6 for b), whose median feature must be located for:
– a) and b) at 2.5 mm from the datum A (2) a) (median plane for the two
opposing faces);
– b) at 18 mm from the datum B constrained perpendicular to A (for a)
and with no distance constraint from B.
A
20
M L
R
21
ISO
1101:2017 and
ISO 5458 : 2018
GEOMETRICAL
CHARACTERISTIC
Symbol:
Type of geometrical
CZ/SZ
specifications
BACK TO CONTENTS
MEANING
EXAMPLE
CZ/SZ
CZ ou SZ
Position
avec CZ/SZ
avec CZ/SZ
TYPE SPECIFICATIONS
The toleranced feature (1) is the group of 4 extracted axes.
nx
nx
TOLERANCED FEATURE
Note: ISO 5458:2018 now uses the location symbol
to stipulate when the specification applies to several
features and that the datum system does not fully
constrain the tolerance zone to indicate modifier SZ
or CZ or CZR.
The tolerance zone (2) is the group (combined zone) of 4 individual tolerance
zones (space within a cylinder with a diameter of 0.2 mm), which must be
positioned with respect to each other, regardless of other features.
Integral
Derived
For a)
For b)
USABLE
MODIFIER
EXAMPLES OF COMPLEMENTARY INDICATIONS
a)
b)
A
M L
F
CZ
UZ
22
A
R
For a): with the modifier SZ, each of the 4 extracted axes considered
separatly (1’), is required to be part of a tolerance zone (2’), which must be
positioned exclusively from to the datum A (3) (axis of the maximum inner
diameter of the cylinder).
For b): with the modifier CZ, all extracted axes (1), considered together
(combined), must be positioned with respect to each other and with respect
to the datum A (3).
23
BACK TO CONTENTS
Type of geometrical
specifications
MEANING
EXAMPLE
ISO
1101: 2017
3
GEOMETRICAL
CHARACTERISTIC
Symbol:
Coaxiality
Concentricity
TYPE SPECIFICATIONS
For any cross section defined, (1) in this case, as a plane perpendicular
to the axis of the cylinder (3) associated with the datum feature B,
the toleranced feature is the centre of the associated circle according
to the least squares (see ISO 17450-3) at the extracted integral line
in each cross section.
The tolerance zone (2) is the space within a circle with a diameter of 0.2 mm,
which must be concentric around the specified datum B established in each
section by the centre of the maximum inscribed circle.
TOLERANCED FEATURE
Integral
Derived
USABLE
MODIFIER
EXAMPLES OF COMPLEMENTARY INDICATIONS
A
M L
R
F
CZ
UZ
The toleranced feature (1) is the extracted axis of the cone.
The tolerance zone (2) is within a cylinder with a diameter of 0.2 mm,
which must be co-axial to the datum B (3).
A
24
M L
R
25
BACK TO CONTENTS
MEANING
Type of geometrical
specifications
EXAMPLE
ISO
1101: 2017
GEOMETRICAL
CHARACTERISTIC
Symbol:
a)
Symmetry
The toleranced feature is for:
a: the extracted median surface (1a);
b: the set of the two extracted axes (for holes) (1b).
The tolerance zone is the space included in for:
a: between two planes at a distance of 0.1 mm (2a);
b: in a common cylinder with a diameter 0.2 mm (2b).
The tolerance zone must be symmetrical around the datum A (3) for a) & b)
and perpendicular to datum B for b) only.
TYPE SPECIFICATIONS
b)
TOLERANCED FEATURE
Integral (not prohibited)
Derived
USABLE
MODIFIER
EXAMPLES OF COMPLEMENTARY INDICATIONS
A
M L
R
F
CZ
UZ
The toleranced feature (1) is the extracted median surface (from the groove).
The tolerance zone (2) is the space between two planes at a distance
of 0.2 mm, where the median feature (3) is constrained from to the datum
system A/B/C; perpendicular to the upper tangent plane A and symmetric
to the datums B & C, which are the axes of the maximum inscribed cylinders
of the cylinders constrained to be perpendicular to the datum A.
A
26
M L
R
27
BACK TO CONTENTS
EXAMPLE
MEANING
Type of geometrical
specifications
ISO
1101: 2017
GEOMETRICAL
CHARACTERISTIC
Symbol:
The toleranced feature (3) is any extracted line established by a cylinder (2)
co-axial to the datum K (1) (taken individually).
The tolerance zone (4) is the space between two circles with the same radius
(as cylinder 2) and equidistant by 0.1 mm, which must be perpendicular
to the datum D (1).
Circular run-out
(simple)
TYPE SPECIFICATIONS
TOLERANCED FEATURE
Integral
Derived
USABLE
MODIFIER
The toleranced feature (3) is any extracted line for an intersection plane (2)
perpendicular to the common specified datum A-B (1) (taken individually).
The tolerance zone (4) is the space between two concentric circles at
a distance of 0.1 mm in the intersection plane (2), which must be co-axial
to the datum A-B (1).
EXAMPLES OF COMPLEMENTARY INDICATIONS
A
A
M
M LL R
R
FF
CZ
CZ
UZ
UZ
The toleranced feature (3) is any extracted line for a 2 angle cone co-axial
to the datum C (1) (taken individually).
The tolerance zone (4) is the space between two parallel circles at a distance
of 0.1 mm, which must have their centers on the datum C (1).
A
28
M L
R
29
BACK TO CONTENTS
EXAMPLE
MEANING
Type of geometrical
specifications
ISO
1101: 2017
GEOMETRICAL
CHARACTERISTIC
Symbol:
Total run-out
TYPE SPECIFICATIONS
The toleranced feature (1) is the extracted integral surface.
The tolerance zone (2) is the space between two cylinders equidistant
by 0.1 mm, which must be co-axial to the common datum A-B (3).
TOLERANCED FEATURE
Integral
Derived
USABLE
MODIFIER
EXAMPLES OF COMPLEMENTARY INDICATIONS
A
A
M
M LL R
R
FF
CZ
CZ
UZ
UZ
The toleranced feature (1) is the extracted integral surface.
The tolerance zone (2) is the space between two planes at a distance
of 0.1 mm, which must be perpendicular at the datum D (3).
A
30
M L
R
31
BACK TO CONTENTS
EXAMPLE
ISO
2692 : 2014
MEANING
See note
MODIFIER
Maximum material
Reciprocity
Breaks with
the independency
principle by
creating a link with
the dimensional
specifications.
Without the maximum material modifier, a part of
the conformance zone (4) cannot be used to allow
the part to be assembled.
A
M L
A
M L
A
M L
TOLERANCED FEATURE
modify the nature
of toleranced feature
from derived to
integral
Note: with the maximum material, if the diameter of the toleranced feature is greater than
the maximum material dimension (12 mm) (for a borehole), then the geometrical tolerance
allocated to the extracted axis will depend on the dimensions of the feature (see dynamic
diagram, no longer used since end-2006).
See note
Note: reciprocity applies
as a complement to
the other two modifiers
&
The toleranced feature (1) is the extracted integral surface (with the maximum
material, the toleranced feature is no longer the derived feature).
The tolerance zone (2) is the space outside of the cylinder with a diameter of
11.8 mm (12 - 0.2), which must be perpendicular to the datum C (3).
F
R
F
CZ
R
UZ
CZ
R
UZ
F
CZ
Without the least material modifier, part of
the tolerance zone (4) cannotUZ
be used to allow
the part to fulfil its expected role.
32
The toleranced feature (1) is the extracted integral surface (with the least
material, the toleranced feature is no longer the derived feature).
The tolerance zone (2) is the space within a cylinder with a diameter of 12.38 mm
(12.18 + 0.2), which must be perpendicular to the specified datum C (3).
Note: with the least material, if the diameter of the toleranced feature is less than the least
material dimension (12.18 mm) (for a borehole), then the geometrical tolerance allocated to
the extracted axis will depend on the dimensions of the feature (see dynamic diagram, no longer
used since end-2006).
33
Modifier
Least material
BACK TO CONTENTS
EXAMPLE
ISO
2692 : 2014
MEANING
MODIFIER
Least material
Reciprocity
Breaks with
the independency
principle:
by creating a link
with the dimensional
specifications.
The maximum material modifier can be used to define
a tolerance zone; a part of the tolerance zone cannot be
used to allow the part to be assembled.
A
M L
A
M L
TOLERANCED FEATURE
modify the derived
toleranced feature
to an integral
Note: the dimensions of the feature must always be within the tolerance interval.
A
M L
Note: reciprocity applies
as a complement to
the other two modifiers
(M or L).
&
The toleranced feature (1) is the combination of two extracted integral
surfaces (1a + 1b).
The tolerance zone (2) is the space in two cylinders with diameters
of 24.15 mm (2a) and 11.95 mm (2b), which shall be co-axial (gauge
consisting of a staged “GO” type cylinder).
F
F
R
F
CZ
R
UZ
CZ
R
UZ
CZ
The principle of reciprocity allows any aspect
UZ
not used for geometrical principles to be transferred
to dimensional features. This modifier can be used
to establish equivalences with 0
or 0 , but with
a narrower dimensional tolerance.
34
The toleranced feature (1) is the combination of two extracted integral
surfaces (1a + 1b).
The tolerance zone (2) is the space in two cylinders with diameters
of 24.15 mm (2a) and 11.95 mm (2b), which must be co-axial (gauge
consisting of a staged “GO” type cylinder).
Futhermore, the reciprocity modifier transforms the upper or lower tolerance
limit of the dimensional specification, by integrating the tolerance of the geometrical specification associated with the least or maximum material modifier
(the upper tolerance becomes 24,15 : 24,05 +0,1 in this case).
35
Modifier
Maximum material
BACK TO CONTENTS
EXAMPLE
ISO
10579: 2017
MEANING
MODIFIER
Free state can be
used to remove a
constraint condition,
for the specifications
in question, when
the rigidity principle
does not apply and
if only the effect
of gravity force is
considered.
ISO 10579-NR Constraint condition: part placed
under a load of 10 daN on a flat surface, in the
direction of gravity.
If the standard ISO 10579-NR is referred to, any specifications are defined
for the constrained condition, unless the modifier
is mentioned in
dimensional or geometrical specifications, in which case the specifications
are defined without using the “free state” (without restrained condition).
A
M L
R
F
CZ
UZ
Technical specifications ISO/TS17863 introduces mobility into assemblies.
Verification condition no. 1 applies with part 1 considered as fixed (FP) A
and to part 2 considered as moveable (MP), while maintaining the orientation
M L R
of the assembly in the direction of gravity no.1.
F
CZ
Verification condition no. 2 applies with moveable part 1 (MP) and fixed UZ
part
2 (FP), while maintaining the orientation of the assembly in the direction of
gravity no.2.
TOLERANCED FEATURE
Integral
Derived
1 = FP 1 - MP 2 , G1
2 = FP 2 - MP 1 , G2
36
37
Modifier
Free state
(no restrained condition)
BACK TO CONTENTS
M L
F
ISO
1101: 2017
CZ
UZ
R
EXAMPLE
MEANING
MODIFIER
Projected tolerance
CZ
UZ
The toleranced feature (1) is: - the extension, over a length of 8 mm
from the datum plane (3a), of the axis (6) of the cylinder associated
with the extracted integral surface, in portion of the axis (6) between
the planes (3a & 4).
The tolerance zone (2) is the space within a cylinder with a diameter
of 0.2 mm constrained to be perpendicular to the primary datum (3a)
and positioned 22 mm from the secondary datum (3b) (itself constrained
to be perpendicular to the primary datum).
The indication of the tertiary datum C followed by modifier , indicates
that the tertiary datum (3c) is constructed from the unconstrained portion (7)
of the associated feature (5) (the aim is not to associate the extracted
integral surface, but to the extend of its associated feature).
TOLERANCED FEATURE
Integral
Derived
Note: the theoretical exact dimensions are given
by the CAD model (digital make-up of the model).
38
39
A
M L
R
F
CZ
UZ
Modifier
F
A
M L
R
Can be used
to consider
the extension
(“projection”) of
a geometrical feature
over a given length
BACK TO CONTENTS
EXAMPLE
ISO
1101: 2017
MEANING
MODIFIER
Common zone
Combined zone
Breaks with the
independency
principle between
several tolerance
zones by integrating
constraints between
the zones in terms
of simultaneous
orientation and
position, to create
a “pattern”.
Note: this is a special case: the tolerance zone, by definition, comprises two co-axial
cylinders with the same diameter, which is equivalent, in this case, to one cylinder with
a diameter of 0.2 mm.
A
M L
R
F
CZ
UZ
The toleranced feature (1) is the combination of two portions of extracted
integral surfaces (1a + 1b).
The tolerance zone (2) is the combination of 4 zones included between
2 planes at a distance of 0.2 mm and mutually constrained in terms
of orientation (90° or 0°) and position (30 and 50 mm).
TOLERANCED FEATURE
Integral
Derived
Note: the constraint between these 4 individual tolerance zones is applied by the modifier CZ,
which breaks with the independency principle for these specifications.
40
41
Modifier
The toleranced feature (1) is the combination of two extracted axes (1a + 1b).
The combined tolerance zone (2) is the space within a cylinder with a diameter
of 0.2 mm, whose axis shall be perpendicular to the datum plane (3).
BACK TO CONTENTS
EXAMPLE
ISO
1101: 2017
A
M L
TOLERANCED FEATURE
The toleranced feature (1) is the extracted integral surface (real surface
of the sphere).
The tolerance zone (2) is the space between two profile surfaces at
a distance of 0.2 defined as equidistant from a feature (4) offset towards
the internal material (“– ”) by 0.5 mm with respect to the nominal shape
of the feature (3) (a sphere with a radius of 20 in this case).
A
Integral
Derived
M L
R
F
CZ
UZ
Variable offset zone
(with reference to
the nominal definition)
a)
b)
Can be used to offset
(+ or –) the nominal
shape of an undefined
value.
TOLERANCED FEATURE
Integral
Derived
b) T he modifier “OZ” has not yet been standardized;
its introduction is planned when revising standards
ISO 1660 and ISO 1101.
42
The toleranced feature (1) is the extracted integral surface (actual surface
of the sphere).
The tolerance zone (2) is the space between two surfaces at a distance
of 0.2 mm for (a) and 0.05 mm for (b) and equidistant from a sphere:
– a) with a fixed radius of 19.5 mm;
– b) with a variable radius.
43
Modifier
A
Can be used to offset
(+ or –) the nominal
shape of a specified
value.
CZ
UZ
R
CZ
UZ
F
Asymmetric zone
(with reference to
the nominal definition)
R
F
M L
MODIFIER
MEANING
BACK TO CONTENTS
EXAMPLE
MEANING
Type de spécifications
géométriques
ISO
1101 : 2017
GEOMETRICAL
CHARACTERISTIC
Symbol :
Surface profile
The toleranced feature (1) is the extracted integral surface.
The tolerance zone (2) is the space contained between two surfaces defined
as equidistant from a feature (6) having the nominal shape (a cone) with its
angle (3) considered as variable (VA) and constrained by the datum system B/A :
coaxial to B(4) and located from A(5) at 20 mm by its gauge plane (defined by a
diameter of 38 mm).
The angular dimensional specification qualifies the global angle of the conical
surface with the minimax criteria (Chebyshev) independently of the form
deviation of the cone.
TYPE SPECIFICATIONS
TOLERANCED FEATURE
Integral ( line/surface )
dérived
USABLE MODIFIER
EXAMPLES OF COMPLEMENTARY INDICATIONS
A
A
M
M LL RR
FF
CZ
CZ
UZ
UZ
44
A
Without the VA modifier, the angle (3) of the reference feature, for evaluation,
median feature of the tolerance zone) is fixed. The geometrical specification
takes into account the effect s of the dimensional variation and the form
variations and the orientation/location variation with the datum system.
45
Modifier
VA
Line profile
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EXAMPLE
ISO
1101: 2017
MEANING
INDICATION
Intersection plane
ou
Can be used to
define a line-type
toleranced feature, the
intersection between
the integral surface
and an oriented plane
(not positioned).
TOLERANCED FEATURE
Integral line
Derived point or line
a)
The toleranced feature is an extracted integral line (1a or 1b) corresponding
to the intersection between the extracted integral surface and an intersection
plane (5a or 5b) constructed using the datum C (4).
The tolerance zone (2a or 2b) is the space between two straight lines
co-planar with the intersection plane (5a or 5b) distant from the tolerance
and which must be:
– a: parallel to the datum plane A (3);
– b: inclined from datum plane A (3) at a specified angle.
Since 2017, the LE (line element) indication is no
longer authorized.
Orientation plane
ou
Can be used to orientate a flat tolerance
zone, applicable to
a derived tolerance
feature.
a)
b)
The toleranced feature is the extracted axis (1).
The tolerance zone (2a or 2b) is the space between two parallel planes
and which must be parallel with the datum A (3) and:
– a: perpendicular to the datum plane B (4);
– b: parallel to the datum plane B (4).
TOLERANCE ZONE
2 planes // oriented
2 straight lines // oriented
46
47
Modifier
b)
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EXAMPLE
ISO
1101 : 2017
MEANING
INDICATION
TOLERANCED FEATURE
Integral surface or line
Derived line or point
Accurate theoretical dimensions see CAD model
No. CETIM5.0
Note: this symbol requires the use of modifier SZ, UF or CZ.
The toleranced feature is the collection of extracted integral surfaces 1a) to 1d),
not including 1e), which is nominally parallel to the collection plane.
The tolerance zone is a combined zone, i.e. a collection of 4 tolerance zones (2a),
2b, 2c and 2d, positionally and orientationally constrained in respect of each other
(CZ) (the dimensions defining the shapes of the features and the constraints are
defined using the CAD model).
INDICATION
All, everywhere
(for the entire part)
Accurate theoretical dimensions see CAD model
No. CETIM5.0
Note: this symbol requires the use of modifier SZ, UF or CZ.
48
The toleranced feature is the collection of all integral surfaces extracted from
the part 1a) to 1e).
The tolerance zone is a combined zone, i.e. a collection of 5 toleranced zones,
2a to 2e, positionally and orientationally constrained in respect of each other
(CZ), the dimensions defining the shapes and the constraints are defined by
the CAD model, defining a conformity volume limited by equidistant minimum
and maximum borders of the theoretical model.
49
Indication
All around (in a given
direction defined by
a collection plane)
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EXAMPLE
MEANING
CZR and SIM
ISO
5458 : 2018
MODIFIER
CZ/SZ/CZR
CZ/SZ/
CZR
TOLERANCED FEATURE
All possibilities
SIMi
Modifier used to
orientationally and
positionally constrain
the tolerance zones
from the specifications
related to the same SIM
label (example SIM1)
CZF
For specifications a) and b), the toleranced feature is the collection of extracted integral surfaces 1a).
Tolerance zones 2a) or 2b) are the collection of 2 tolerance zones, i.e. the area
between two planes and respective distances of 0.05mm and 0.15 mm.
The two tolerance zones 2a and 2b respectively are only orientationally
constrained in respect of each other (CZR (since the distance between the
two zones (2a) is variable), and orientationally and positionally (CZ) (since
a distance of 10 mm was imposed between zones 2b)
Note: the label number allocated to the SIM modifier can
be omitted if there is only one grouping level.
For the specifications c), the SIM modifier imposes a position constraint relative
to all their tolerance zones:
– The toleranced feature is the collection of all extracted integral surfaces 1a)
and 1b).
The toleranced zone is the collection of 4 tolerance areas, since 2c1 and 2c2
are 0.25 mm and 2c3 and 2c2 are 0.5 mm constrained orientationally and positionally in respect of each other (SIM).
50
51
Modifier
CZR
Combined zone
with constrained
orientation only
EXAMPLE
ISO
5458 : 2018
SZ/CZ/CZR
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MEANING
a
MODIFIER
b
Modifier sequence
SZ/CZ/CZR
Consideration for the
repetition of features
(example between
groups of groups of
features)
For the specification a) and b), there are four independent groups (SZ). Each
group is managed by a combined zone (CZ), composed of 2 cylindrical zones
positionally constrained in respect of each other.
For specification a), there is no external constraint provided by a datum.
However, for specification b) the combined zones are additionally constrained
positionally in relation to datum B at 20 mm.
Séquence
TOLERANCED FEATURE
All possibilities
c
Note 1: here there are four groups A, each composed of two B
features.
d
Note 2: the order of the sequence SZ, CZ, CZR resumes the order
above of the specification.
As such, in the specification
– a) and b) the A groups are considered independently from
one another (SZ) and in the A group the B features are not
considered to be independent (CZ).
– c) and d) the A groups are not considered to be independent
from one another (CZ) and naturally in the A groups the B
features are not considered to be independent (CZ).
52
For the specification c) and d), there are four groups constrained positionally
and orientationally in relation to one another (1st CZ) (3x0° and 3x30 mm).
Each group is initially managed by a combined zone (2nd CZ) composed of two
cylindrical zones constrained positionally between them.
For specification c), there is no external constraint provided by a datum.
However, for specification d), the combined zones are additionally constrained
positionally in relation to the datum system B B|A at 20 mm and 24 mm
respectively.
53
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EXAMPLE
ISO
13715 : 2014
MEANING
The Nominal shape
of the edge is not
indicated (defined)
on the drawing, but
an edge may exist on
the workpiece.
The extracted edge
must be part
of a zone.
INDICATION
Edge of
undefined shape
a
b
The “+” sign authorises more material
The zones are not defined precisely in the standard, therefore we have given
our widest possible interpretation.
The “–” sign authorises less material
a
b
No “vertical” overshooting
is authorised (tolerances
indicated above the symbol).
No “horizontal” overshooting is
authorised (tolerances indicated
next to the symbol).
54
55
Edge of undefined shape
a
b
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GLOSSARY
GLOSSARY
GPS:
Geometrical Product Specifications
Invariance class:
one of seven groups of geometrical features
with the same invariance degrees : planar,
cylindrical, spherical, revolute, prismatic, helicoidal or complex.
Constraint:
the term “constraint” is used to establish an
associated feature to orientate or locate it.
The notion of requirement will sometimes be
used instead of constraint to simplify understanding.
Dimension line:
representation of a dimension on a drawing.
Degree of invariance:
translation or rotation motion leaving the feature unchanged (considered complete).
Single features:
geometrical features which cannot be broken
down into other features with less degrees of
invariance.
Toleranced feature:
geometrical feature to which a GPS specification is applied.
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Feature of size:
single or composite geometrical feature with
having a size considered as variable.
Specification uncertainty:
“interpretability” of a specification.
Correlation uncertainty:
imperfection of the correlation between a functional need and a set of specifications.
Offset profile:
the standard refers to an “offset profile”, considering that the offset is applied at every point
of the feature considered, depending on the
direction of the normal vector.
Tolerance zone:
authorised variation area for a toleranced feature having its degrees of freedom constrained
or not from datums or datum systems.
Datum:
collection of a plane, straight line and / or point
used to lock one or more degrees of freedom
defined from an associated feature*.
*Note: a datum is the situation features of an associated
feature established from an extracted integral feature.
57
NO
T
CA
R
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Avec le soutien de :
Author: Rénald Vincent, Cetim
ISO TC 213 / WG 2 and WG 14 convener
ISO 5459, ISO 14405-1, ISO 5458… project leader
©
CENTRE TECHNIQUE DES INDUSTRIES MÉCANIQUES (CETIM), 2018
TECHNICAL CENTER FOR MECHANICAL INDUSTRY
ISBN: 978-2-36894-158-4
“This publication may not be reproduced or represented, in part or in whole, by any means, without the
permission of CETIM. This would represent a counterfeit. Only reproductions which are strictly reserved
for the private use of the copier and not intended for collective use and, furthermore, analyses and short
quotations justified by the scientific or informative nature of the target publication, are authorised”
(French Code of intellectual property, articles L. 122-5 and L. 335-2).
Cover photo credit: Cetim, Ch. Barret
Printing: Calligraphy, Châteaubourg
10-31-1614
58
ISO - GPS memo
Examples and meanings
Edition 2018
“The GPS provides a means of communication whereby
designers, production engineers, quality experts, inspectors and metrologists can exchange information on the
allowable geometries of workpieces manufactured on the
basis of specifications... indicated on a drawing... The associated graphic and symbolic “language” uses the syntax and
semantics defined in GPS standards”. This document, which
is in the diffusion of GPS system contribute , is intended as
a practical resource, a summary of GPS standards on tolerancing, aiming to provide new contributions to the main
features contained in the basic tolerancing and dimensioning
standards released since the publication of the first Memo.
N° Cetim : 4C17
1806–054
ISBN: 978-2-36894-158-4
cetim.fr
Centre technique des industries mécaniques
52, avenue Félix-Louat, CS 80067
60304 Senlis Cedex