MarForm.Form and Location Tolerances

General notes on form and location tolerances

A form and location tolerance of a feature (surface,axis, point or median plane) defines the zone withinwhich every point of this feature is to be contained.According to the feature to be toleranced and themanner in which it is dimensioned, the tolerancezone is one of the following:• the area within a circle• the area between two concentric circles• the area between two parallel, straight lines• the area between two equidistant lines• the space between two parallel planes• the space between two equidistant surfaces• the space within a cylinder• the space between two coaxial cylinders• the space within a parallelepiped

For location tolerances, it is necessary to define adatum indicating the exact location if the tolerancezone. A datum is a theoretically exact, geometricalfeature (e.g. axis, plane, straight line, etc.); datums canbe based on one or several datum features.The toleranced feature may be on any form,location or orientation within the tolerance zone,unless a more restrictive indication is given.The tolerance value t is indicated in the same unitused for linear measurements. If not otherwisespecified, the tolerance.

FLATN ESSDIN ISO 1101

STRAIG HTN ESSDIN ISO 1101

CON ICITYnot yet described by standards

ANGULAR SECTORnot yet described by standards

FOR MTESTE R–EVALUATION M ETHODSe.G. DIN ISO 6318

DefinitionThe tolerance zone is limited in themeasuring plane by two parallelstraight lines a distance t apart.

ExamplesAny generating line of the tolerancedcylindrical surface shall be containedbetween two parallel, straight lines0.1 apart.

Any portion of length 200 of anygenerating line of the tolerancedcylindrical surface shall be containedbetween two parallel, straight lines0.1 apart.

NoteFor further straightness tolerances,see ISO 1101.

DefinitionThe tolerance zone is limited bytwo parallel planes a distance tapart.

ExampleThe toleranced surface shall becontained between two parallelplanes 0.08 apart.

GE NERAL TOLE RANCES [mm]for machined workpieces, DIN ISO 2768

Regression straight line(Gaussian straight line)Mean line laid throught the measuredprofile such that the sum of the squares ofall profile deviations is a minimum.

(LSS = Least Square Straight line)

Enveloping parallel linesParallel, straight lines enclosing the profileand having the least separation.

(MZS = Minimum Zone Straight lines)

Regression parabolaMean parabola (2nd order) laid through theprofile such that the sum of the squares ofall profile deviations is a minimum.

(LSP = Least Square Parabola)

Edge identifikationThe position of a profile interruption (edge)is determined. The profile is evaluated up tothe edge according to LSS.

(EID = EdgeIDentification)

Regression circle(Gaussian straight circle)Circle laid into the measured circular profilesuch that the sum of the squaresof all profile deviations is a minimum.

(LSC = Least Square Circle)

Circular zone with minimumradial separationConcentric circles enclosing the circular pro-file and having the least radial separation.

(MZC = Minimum Zone Circles)

Minimum circumscribed circleSmallest possible circle which can befitted around the circular profile.

(MCC = Minimum Circumscribed Circle)

Maximum inscribed circleLargest possible circle which can be fittedwithin the circular profile.

(MIC = Maximum Inscribed Circle)

Reproduced with the permission of the DIN Deutsches lnstitut fur Normung e.V. (German Institute forStandardizatlon). When applying the standard, the latest version available from Beuth Verlag GmbH,Burggrafenstrasse 6, 10787 Berlin, will be relevant.

3752684 - 1.10.2006 - Printed in Germany

Mahr GmbH .P.O . Box 1853 . D-37073 Göttingen . Phone +49 (0) 551-7073-0 . Fax +49 (0) 551-71021

DefinitionThe tolerance zone is limited in themeasuring plane by two straight linesa distance t apart and parallel to thedatum. Not the measured profile, butthat section of the reference straightline calculated according to LSS whichis restricted to the measuring lenghtshall be contained within the tolerancezone.

ExampleEach section of a reference straight linecalculated according to LSS which ismeasured on the toleranced, cylindricalsurface shall be contained betweentwo straight lines 0.04 apart andparallel to the opposite generating line.

NoteThe parallelism deviation may begreater, if necessary, it can betoleranced separately.

DefinitionThe tolerance zone is limited inthe measuring plane perpendi-cular to the axis by two con-centric circles a distance apart.The measured circumferenceshall be contained in anyangular sector t starting fromthe profile centre within thetolerance zone.

ExampleThe “local“ roundness deviationshall be smaller than 0.012 inany angular sector starting fromthe profile centre and featuringa width of 15°.

NoteThe roundness deviation as perISO 1101 may be greater, ifnecessary, it can be tolerancedseparately.

Tolerance class H

Range of > 10 > 30 > 100 > 300 > 1,000

nom, lenght ... 10 ... 30 ... 100 ... 300 ... 1,000 ... 3,000

0.02 0.05 0.1 0.2 0.3 0.4

0.2 0.3 0.4 0.5

0.5

0.1

Tolerance class K

Range of > 10 > 30 > 100 > 300 > 1,000

nom, lenght ... 10 ... 30 ... 100 ... 300 ... 1,000 ... 3,000

0.05 0.1 0.2 0.4 0.6 0.8

0.4 0.6 0.8 1

0.6 0.8 1

0.2

Tolerance class L

Range of > 10 > 30 > 100 > 300 > 1,000

nom, lenght ... 10 ... 30 ... 100 ... 300 ... 1,000 ... 3,000

0.1 0.2 0.4 0.8 1.2 1.6

0.6 1 1.5 2

0.6 1 1.5 2

0.5

RoundnessThe general tolerance on roundness is the minimumformed by the diameter tolerance and the generaltolerance on run-out.

ParallelismThe general tolerance on parallelism is the maximumformed by the dimensional tolerance and the generaltolerance on straightness/flatness.

ROU N DNESSDIN ISO 1101

CYLI NDR ICITYDIN ISO 1101

AN G U LAR IT YDIN ISO 1101

PO SITIONDIN ISO 1101

LI NE PROFILEDIN ISO 1101

CONCENTR ICITY /COAXIALITYDIN ISO 1101

SURFACE PROFILEDIN ISO 1101

SYM METRYDIN ISO 1101

PARALLE LISMDIN ISO 1101

PERPENDICULARITYDIN ISO 1101

TOTAL RUN-OUTDIN ISO 1101

RADIAL RUN-OUTDIN ISO 1101

DefinitionThe tolerance zone is limited in themeasuring plane perpendicular tothe axis by two concentric circles adistance t apart.

ExampleThe circumference of any cross-section of the toleranced cylindricalsurface shall be contained betweentwo concentric circles 0.1 apart.

DefinitionThe tolerance zone is limited bytwo coaxial cylinders a distancet apart.

ExampleThe toleranced cylindrical surfaceshall be contained between twocoaxial cylinders 0.1 apart.

DefinitionThe tolerance zone is limited bytwo parallel planes a distance tapart and inclined at the specifiedangle to the surface.

ExampleThe tolerance surface shall becontained between two parallelplanes 0.05 apart which are in-clined at 12° to the datum axis A.

DefinitionIf the tolerance value is precededby the sign [, the tolerance zone islimited by a cylinder of diameter t,the axis of which is in thetheoretically exact position of thetoleranced line.

ExampleThis axis of the toleranced boreshall be contained within acylinder of diameter 0.02, the axisof which is in the theoreticallyexact position with respect to thesurfaces A and B.

NoteFor the positional tolerance of apoint or a plane, see DIN ISO 1101.

DefinitionThe tolerance zone is limited bytwo lines enveloping circles ofdiameter t, the centres of whichare situated on a line having thetrue geometrical form.

ExampleIn each section parallel to the planeof projection, the toleranced profileshall be contained between twolines enveloping circles of diameter0.04, the centres of which aresituated on a line having a truegeometrical form.

DefinitionThe tolerance zone is limited bytwo surfaces enveloping spheresof diameter t, the centres of whichare situated on a surface havingthe true geometrical form.

ExampleThe considered surface shall becontained between two surfacesenveloping spheres of diameter0.02 the centres of which aresituated on a surface having thetrue geometrical form.

Definition (coaxiality)The tolerance zone is limited by acylinder of diameter t, the axis ofwhich coincides with the datumaxis.

Example (coaxiality)The axis of the toleranced cylindershall be contained within a cylinderof diameter 0.08 coaxial with thedatum axis A.

NoteFor concentricity tolerance, seeDIN ISO 1101.

DefinitionThe tolerance zone is limited bytwo parallel planes a distance tapart and symmetrically disposedto the median plane with respectto the datum axis or datum plane.

ExampleThe median plane of a slot shall becontained between two parallelplanes which are 0.08 apart andsymmetrically disposed to themedian plane with respect to thedatum feature A.

NoteFor symmetry tolerance of a line oran axis, see DIN ISO 1101.

DefinitionThe tolerance zone is limited inthe measuring plane by twostraight lines a distance t apartand parallel to the datum.

ExampleAny generating line of thetoleranced surface shall becontained between two straightlines 0.1 apart and parallel to thedatum surface A.

NoteFor further parallelism tolerances,see DIN ISO 1101.

DefinitionThe tolerance zone is limited inthe measuring plane by twoparallel, straight lines a distancet apart and perpendicular to thedatum.

ExampleAny generating line of the toler-anced cylindrical surface shall becontained between two straightlines 0.1 apart and perpendicularto the datum surface.

NoteFor further perpendicular toler-ances, see DIN ISO 1101.

DefinitionThe tolerance zone is limited in themeasuring plane perpendicular tothe axis by two concentric circles adistance t apart, the common centreof which lies on the datum axis.

ExampleThe circumference of any cross-section of the toleranced cylindricalsurface shall be contained betweenconcentric circles 0.1 apart, thecommon centre of which lies onthe datum axis formed by A and B.

NoteWhen taking the measurement, theworkpiece has to be turned aboutthe datum axis. For axial run-outand run-out tolerances in any or aspecified direction, see DIN ISO 1101.

Definition (total axial run-out)The tolerance zone is limited bytwo parallel planes a distance tapart and perpendicular to thedatum axis.

Example (total axial run-out)The toleranced surface shall becontained between two parallelplanes 0.1 apart and perpendicularto the datum axis D.

NotesWhen taking the measurement,the workpiece has to be turnedaround the datum axis severaltimes. Workpiece and measuringinstrument have to move radiallyto each other.For total radial run-out, seeDIN ISO 1101.