Circular runout and other controls

[aniiben]

I got a question from one of the engineers:

When a circular runout (not total runout) is specified on the print (let's say circular runout within 0.1mm on a cylindrical surface to datum feature A) is the derived median line straightness also controlled (within the same tolerance value)?

What about the concentricity? Is the concentricity also controlled within the same tolerance value as the circular runout?

The reinforce: I am talking about the circular runout (not about total runout) comparison.

Not sure those two questions are “yes/no” questions (straight forward answers), but I am putting them up for discussion.

 

[Belanger]

Similar thing discussed here:
[URL unfurl="true"]https://www.eng-tips.com/viewthread.cfm?qid=422237[/url]



John-Paul Belanger
Certified Sr. GD&T Professional
Geometric Learning Systems

 

[aniiben]

Thank you J-P Belanger to the above link of a similar discussion.
I found it very evolved, but also enlightening.


What starts me to ask the initial question is a statement the engineer found in a reputable GD&T material for basic GD&T training.
The statement reads something like:
“When circular runout is specified then circularity, position, concentricity and derived median line are also being controlled”


Our senior engineer does not have any issues with circularity and position, but he is not quite sure about derived median line and concentricity, hence my questions.

What do you think about the above statement? Looks like can be misleading, at least from my point of view, since it is way too general and it is not mentioning the size tolerance………………………….
Am I correct?

 

[CheckerHater]

On the enclosed illustration the tighter runout tolerance is, the less space is left for part surface variation, and subsequently, for derived median play.


"For every expert there is an equal and opposite expert"
Arthur C. Clarke Profiles of the future

 

[greenimi]

https://www.youtube.com/watch?v=NArW09DFhf8

"GD&T Tip - Does Runout Equal Concentricity?

This video is talking about median points too (along with runout and concentricity and their relationship).
Hope it helps somehow.