circularity tolerance greater than the size tolerance without using "AVG"

[UchidaDS]

thread286-298925

I had look thru most of the thread but can't find the answer.
If I have a part diameter of 14.000" +/-.005", and the call out for circularity is .100 (F). I know this is a free state part, but there is no "AVG" called out for this feature.
So, for this case, what would be the max or min of the diameter? Or there is a typo in the print?
Thanks for the help!

 

[UchidaDS]

Let me give more detail:
As I notice from the ASME Y14, "AVG" comes with the size tolerance and the feature (circularity) tolerance is greater than size tolerance, it is "valid"; and we can have minimum 4 measurement and get the average. That I have no question about it.
Now, if the drawing is missing "AVG", and the feature tolerance is greater than size tolerance, what should be the acceptable diameter? Or this is a typo?

 

[powerhound]

If the part is a non-rigid part then I would be inclined to believe it is an inadvertent omission. If it is a rigid part then unless there is a circle I or a note that say "PERFECT FORM AT MMC NOT REQUIRED," it is just wrong. Can you show us the print?

John Acosta, GDTP S-0731
Engineering Technician
Inventor 2013
Mastercam X6
Smartcam 11.1
SSG, U.S. Army
Taji, Iraq OIF II

 

[UchidaDS]

Attached. The default size tolerance is +/-.005".
Nothing showing "PERFECT FORM AT MMC NOT REQUIRED".

-By the way, if it indicate "PERFECT FORM AT MMC NOT REQUIRED", what should be the spec of measurement?
-Regardless of the feature tolerance, if I make a "gage" to check the maximum diameter, and if the part does not fit in, can I say it is out-of-round? The gage is as simple as a block having a 14.006" diameter cutout.

 

[Belanger]

It might be OK because note #4 tells us that the size dimension is to be verified while the part is clamped. Even without the note "PERFECT FORM AT MMC NOT REQUIRED," the inherent circularity of .010 (from the diameter callout) is only within the restrained state.

The circularity tolerance of .100 is to be checked in the free state, so it's a different situation. In the Y14.5 standard (2009 edition, end of paragraph 5.5.1) it says that the F symbol "separates the free-state requirement from associated features having restrained requirements." Because of this separation, I see it as being a different requirement than Rule #1 and thus legal.

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

 

[UchidaDS]

1. So is that mean it has to fulfill either one of the requirement, or BOTH?

2. If for the second condition (circularity tolerance of .100", at free state), but it is without the "AVG" (as per drawing), what would be the max/min diameter? Is it still valid to use this AVG (average) method:

==taking at least four measurements and average it up and average value should be within the size tolerance; the data of measurement should fall in one of the condition:

Condition 1: 14.005+.100=14.105 (high) and 14.005-.100 = 13.905 (low)
OR
Condition 2: 13.995-.100 = 13.895 (low) and 13.995+.100 = 14.095 (high)

OR
???

Thanks for the help!

 

[Belanger]

All tolerances on the print have to be met on their own. There is no spec for the diameter of the part in the free state, so no concern about AVG. Just check the diameter (local size and envelope size) in the clamped state, the position in the clamped state, and the circularity in the free state.

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

 

[UchidaDS]

Thanks Belanger!
But why there is no spec for the diameter in the Free state? Is it because of the "NOTE"?

 

[Belanger]

If the part functions in the restrained condition, then that's really the only diameter they care about.
I think the purpose of the circularity in the free state here is just to make sure that the shape is somewhere in the ballpark of the correct shape, so that the part isn't overly stressed when restrained to its real, functional condition.

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