GD&T - Cylindricity VS Rule 1

[[Ke...]]

Sanity check...

ASME Y14.5 at the current revision

Scenario:
A cylindrical feature has a specification of 22.0 +/- 0.02
There is also a Cylindricity callout for the feature of 0.05

Typically, the Cylindricity is a refinement of the form requirement (less than the total allowed deviation in size)

Q:
Does the Cylindricity callout override Rule 1, and allow a greater deviation of form?
or
Is the Cylindricity callout unnecessary, as Rule 1 controls form tighter than the stated Cylindricity requirement?

[[Ch...]]

Keith ,

EDIT : (quoted from GDT Basics)
Due to the Taylor’s/envelope principle your size cannot ever exceed your form meaning the largest envelope it could be would be is always the size tolerance. This is assuming you are using the ASME standard or the ISO standard with the Envelope rule (E with a circle around it) in your print.

Basically, the rule simply stated is : perfect form at MMC.


However - just for imagination - theoretically I think it's possible, if size applies 'locally', and someone machines a shaft more like a noodle.. 🤣

[[Th...]]

Assuming ASME didn't change this in 2018, the only form controls that override the envelope are straightness and flatness.