CYLINDRICITY

FORM

Controls the form of an entire cylindrical surface

✓ NO DATUM NEEDEDASME Y14.5-2018 §12.4

Cylindricity controls the form of a complete cylindrical surface — combining straightness, circularity, and taper into a single control. All points on the surface must fall within a tolerance zone defined by two coaxial cylinders. It is one of the most stringent form controls available.

WHEN TO USE IT

Use cylindricity when the entire cylindrical surface must be highly accurate — such as precision shafts, hydraulic pistons, or bearing journals where both roundness and straightness of the full surface are critical. Because it controls everything simultaneously, it is more restrictive than circularity or straightness alone.

COMMON MISTAKES

Adding a datum reference — cylindricity controls form only and never uses datums

Confusing cylindricity with circular runout or total runout — runout controls relative to a datum axis, cylindricity does not

Applying cylindricity to non-cylindrical features

Specifying a cylindricity tolerance larger than the size tolerance — conflicts with Rule #1

IS YOUR CALLOUT CORRECT?

Check these before releasing your drawing.

Is the FCF free of any datum reference letters?

Cylindricity is a form control. No datum reference should appear.

Is the feature a complete cylinder (not a partial arc or flat)?

Cylindricity only applies to full cylindrical surfaces.

Is cylindricity the right control, or would total runout serve better?

If the axis relationship to other features matters, runout controls relative to a datum.

RELATED SYMBOLS

OTHER FORM CONTROLS

⏥Flatness ⏤Straightness ○Circularity

Redprint checks cylindricity automatically

Redprint flags cylindricity FCFs with datum references and checks for conflicts with size tolerances on the same feature.

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