Diameter Size and Cylindricity

Question

Can you have an out of tolerance diameter but good cylindricity results?

Neil Challinor · Accepted Answer

For cylindricity the tolerance zone is dynamic, meaning it is two cylinders of perfect form that can both grow and shrink simultaneously. The upper boundary will contact the UAME (unrelated Actual Mating Envelope) - so it will be external to material, tangential to the high point(s). The lower boundary will be coaxial to the upper boundary and offset inwards by the cylindricity tolerance amount. 
 Under ASME, the form of the feature can not exceed the boundaries of size - which is why we report UAME and local size with the Geometric Tolerance command. UAME captures the mating envelope (largest size, external to material for and O/D) and local size captures the other size limit (smallest size for an O/D). The difference between the UAME and local size would be the form. If required, the designer can add a cylindricity requirement to further refine things and restrict the form by more than the size tolerance alone allows.

Zen Cat · Answer

The tolerance zone of what? 
 The tolerance zone of the diameter is based on whatever means it's communicated. It can be controlled by the blueprint callout, the CAD model if that model is used as the master definition, etc. That's drawing/company specific. 
 If you're talking about the cylindricity tolerance zone, see the image above that Malgorzata posted. It's 2 concentric cylinders spaced apart by the tolerance called out, best fit around the cylinder releasing all 6 degrees of freedom, which all points must lie within.