POSITION

POSITION

Circularity is the form tolerance. 

It’s 3D Tolerance.

It is independent of datum.

Cylindricity controls the surface of a cylindrical surface to lie within two concentric cylinders.

 GD&T Symbol:                 

Relative to Datum:              NO

MMC or LMC applicable: NO

 

Drawing Callout:

Feature control frame with Cylindricity symbol can be indicated by leader arrow pointing to the surface.

Feature control frame does not contain datum box.

Image: Drawing shows how to apply tolerance 

Tolerance Zone:

Entire referenced surface must lie within two concentric cylinders.

Image: Tolerance zone within the surface of the cylinder can lie 

.The blue zone in the above image shows, the allowable zone within which surface of the cylindrical part should be.

The Cylindricity is 3D version of Circularity, 

As circularity concern of measuring the points in one circle only, The Cylindricity concern of measuring the all points of the surface which fall in tolerance zone.