CYLINDRICITY

THE INSTITUTE FOR ENHANCEMENT OF TECHNOLOGY

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CYLINDRICITY


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Cylindricity

Cylindricity refers to a condition of a surface, whichforms a cylinder where the surface elements in crosssections parallel to the axis are straight and parallel and incross sections perpendicular to the axis are round.Cylindricity thus combines in one term geometrical formtolerances for roundness, straightness and parallelism ofthe surface elements.


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Cylindricity tolerances can only be applied to cylindrical

surface, such as round holes and shafts.

No specific geometrical tolerances have been devised for other

circular forms, which require the use of several geometrical

tolerances.

A conical surface, for example, must be controlled by a

combination of tolerances for roundness, straightness, and

angularity.

Cylindricity


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Cylindricity

Errors of Cylindricity may be caused by out of roundness, like ovality or

lobing

Errors of straightness caused by bending or by diametral variation

Errors of parallelism like conicity or taper

Random irregularities from a true cylindrical form.


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CYLINDRICITY SYMBOL

• The geometric characteristic symbol for cylindricity consists

of a circle with two tangent lines at 60.

• The circle diameter is 62% of the height of the feature

control symbol frame.


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• The Cylindricity tolerance symbol is used in a feature control symbol

• Directed to the cylindrical surface, in either the side view or end view

CYLINDRICITY TOLERANCE DIRECTED TO EITHER VIEW.

CYLINDRICITY TOLERANCE


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A Cylindricity tolerance specifies a tolerance zone consisting of the annular space between two coaxial cylinders, having a difference in radii equal to the specified tolerance zone of 0.05 on radial dimension.


PERMISSIBLE FORM ERRORS


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When the part is at the maximum diameter limit the major diameter of the Cylindricity tolerance zone would likely be larger than the maximum diameter limit.This may be due to lobing, and other irregularities or bending.

DIAMETER OF THE TOLERANCE ZONE MAY BE

LARGER THAN MAXIMUM DIAMETER OF THE PART


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Checked by revolving in vee-blocks while taking indicator readings on the

top surface, in a manner similar to methods described for the measurement of

roundness

The roundness near both ends is first checked by making indicator readings

directly over blocks of varying angles to ensure that lobing will not

significantly affect the results.

The part is then mounted in identical short length vee-blocks, which are

located at each end of the part

PART IN VEE – BLOCKS FOR CYLINDRICITY TESTS

MEASURING METHODS


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Cylindricity tolerances are applicable to internal cylindrical surfaces, such as round holes.

Measurement

• Large holes can be assessed by means of indicator or electronic gauges.

• Best method is to assess the holes with a plane round GO gauge of

length at least equal to the full length or depth of the hole and having the

diameter equal to the max. material size minus the specified tolerance

CYLINDRICITY OF HOLES

CYLINDRICITY

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