gd&t cylindricity

8/10/2019 GD&T Cylindricity

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GD&T Form Table of ContentsReturn to the Previous Slide Slide 1 QuitMaster Table of ContentsGlossary

FORM CONTROLS

CYLINDRICITY
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CYLINDRICITY

Cylindricity: A condition of a surface of revolution in which all points on the surface are

perpendicular and equidistantfrom a common axis. Cylindricity can control

straightness and circulari ty

Cylindricity Tolerance: A 3D boundarydef ined by two theoretically perfect coaxial

cylinderswithin which all the elements of the specified surface must lie.

Cylindricity (3D) Tolerance Zone: The radial distance between the two coaxial cylinders

defines the tolerance zone and represents the amount that surface elements are allowed

to vary from a perfect cylinder. This numerical value (always less than one-half of the

diametrical tolerance) is specified in the tolerance cell of the feature control frame.

Note: As a surface form control, cylindricity is always considered RFS, and the physical

limits imposed by size dimensions cannot be violated. Datums are neither proper nor

allowed in the feature control frame, and the tolerance cannot be modified to consider

additional tolerance as departure from MMC occurs. A diameter symbol zone

descriptor cannot be used in the feature control frame.

Tolerances Of FormCylindricity

Definitions of Terms


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When cylindricity control is applied to an externalfeature, the outer boundary

(larger cylinder) is typically established by circumscribing the high points of thesurface. The inner boundary is radially smaller by the amount of the specified

tolerance. The feature, at any point of measurement (a plane, perpendicular to the

axis), must be within the limits of size.

Tolerances Of Form - Cylindricity


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When cylindricity control is applied to an internalfeature, the inner boundary (smaller

cylinder) is typically established by gage contact with the high points of the surface.

The outer boundary is radially larger by the amount of the specified tolerance. The

feature, at any point of measurement, must be within the limits of size.


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GEOMETRIC CONTROLFOR CYLINDRICITY


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The geometric control for cylindricity is a featureformtolerance which controls

circular, longitudinal, and parallel elements of the featuresurface elementsonly.

Because it is strictly a surface element control, datums are neither proper nor allowed.

As is the case with all surface controls, cylindricity always applies regardless of feature

size.

Because cylindricity can onlybe applied to features and cannot be applied to features

of size, material condition modifiers cannotbe used with a cylindricity specification.

The size envelope imposed by dimensional limits and Rule #1 are never overridden by

a geometric tolerance for cylindricity, and the geometric tolerance becomes the

controlling factor only when departure from MMC exceeds the cylindricity tolerancevalue. Therefore, the virtual conditionof the controlled feature is notaffected.


OVERVIEW


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0.4

A feature control frame describing cylindricity control may be called out in either

view and is applied by using a leader line, as shown.

0.4OR

Verifying Cylindricity Geometric Tolerance


8/15GD&T Form Table of ContentsReturn to the Previous Slide Slide 8 QuitMaster Table of ContentsGlossary

0.4

Tolerance zone is two

coaxialcylinders


Multiple-section

measurements are

taken just like the

measurements for

circularity, except thegauge is NOT reset

between sections.



0.4

Smallest true cylinder

that circumscribes

the high points

of the feature

diameter.

0.4 Radial Distance

Tolerance zone is two

coaxialcylinders




0.2

10.5

9.5

The size tolerance zone consists of two coaxial

cylinders, 0.5 mm apart. This tolerance defines

the actual local size limits.

Cylindricity Geometric ToleranceAlways RFS



0.2

10.5

9.5

The cylindricity tolerance zone consists of two

coaxial cylinders, 0.2 mm apart. This tolerance

can float within the larger size tolerance.


The size tolerance zone consists of two coaxial

cylinders, 0.5 mm apart. This tolerance defines

the actual local size limits.



Coaxial cylinders establish the

tolerance zone for feature cylindricity.


Feature size tolerance. (While

surface elements are restricted to

the refined tolerance zone, the

actual local [measured] sizeof

the cylindrical feature may vary

within the larger boundaries.)

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Coaxial cylinders establish the

tolerance zone for feature cylindricity

(RFS).

At any measuring position, allsurface elements must be within

the cylindricity tolerance zone.

They may vary within the zone,

and the entire zone may expand

or contract within the larger size

tolerance.


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The cylindricity tolerance zonemay extend beyond the lower

limit of the size tolerance, but

no elements on the surface can

be located outside of those

limits. That part of the tolerance

would be sacrificed.


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The geometric tolerance forcylindricity becomes the

controlling factor only when

departure from MMC exceeds

the cylindricity tolerance value.


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gd&t cylindricity

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