Runout with MMC/MMB on DRF? No. Profile with MMC/MMB on DRF? Yes
Runout with MMC/MMB on DRF? No. Profile with MMC/MMB on DRF? Yes
(OP)
What could be the reason that for profile tolerance, MMC/MMB modifier on the DRF (datum shift) is allowed per the standard, but for the runout using MMC/MMB in the same place (DRF-datum shift) is illegal (why the tolerance zone cannot be moved, translated/rotated with runout callout). Both GD and T tools we are checking the surface.
Thank you
Thank you





RE: Runout with MMC/MMB on DRF? No. Profile with MMC/MMB on DRF? Yes
Runout will control surface wrt axis. Apples and oranges?
RE: Runout with MMC/MMB on DRF? No. Profile with MMC/MMB on DRF? Yes
Others on this forum have pointed out that runout is a little unusual because it is defined in the standard based on its inspection method.
John-Paul Belanger
Certified Sr. GD&T Professional
Geometric Learning Systems
http://www.gdtseminars.com
RE: Runout with MMC/MMB on DRF? No. Profile with MMC/MMB on DRF? Yes
In 2009 world you can define profile wrt “complex shape” which doesn’t have an axis at all (at least position of axis is arbitrary).
Runout requires by definition axis derived RFS to begin with. This if what I meant.
We are talking two completely different tools used to achieve two completely different goals.
Is “why screwdriver is different from wrench?” legitimate question, or just troll?
And I simply cannot help but notice that runout is not unique; cylindricity / roundness also comes with inspection method attached; just because it is hidden in separate book, doesn’t make it less true. Also I would avoid such patronizing term as “wobbling”; depending on the design intent runout may be legitimate replacement for concentricity and position. In that sence runout is no less powerfull than profile.
Of course, if grandma had mustache, she’d be grandpa. If you somehow defined runout at MMB it would be not much different from profile.
RE: Runout with MMC/MMB on DRF? No. Profile with MMC/MMB on DRF? Yes
Profile itself can be applied to a complex shape, but that's getting to the point I was making: that runout has a more focused purpose than profile, which means that it's going to have more focused rules such as the RMB requirement.
And I don't see why wobble is a patronizing term; I was merely trying to use layman's terminology to muse about the differences between runout and other geometric characteristic controls. Certainly runout is more involved than such a casual term, but that's a perfectly valid way to explain the root intent of where runout came from. Profile is intended to be a more broad concept, so it doesn't need to have such a stringent rule about using modifiers on the datums.
The bottom line is that runout can't use MMB because that's the way they wrote the rulebook :)
John-Paul Belanger
Certified Sr. GD&T Professional
Geometric Learning Systems
http://www.gdtseminars.com
RE: Runout with MMC/MMB on DRF? No. Profile with MMC/MMB on DRF? Yes
From the top of my head I cannot find legitimate use for axis derived at MMB.
Is it even legal? Is there a good example somewhere?
I am not trying to pick a fight, just curious.
For example, any CAD data has 0 point and XYZ, so you always can derive point and three axis from any “mathematically defined” surface, no matter how ugly. But is there any good use for axis that shifts?
RE: Runout with MMC/MMB on DRF? No. Profile with MMC/MMB on DRF? Yes
I understand datum shift when controlling position of the bunch of holes.
Since OP was about runout, I am still thinking about controlling some sort of coaxiality / eccentricity condition.
What do we gain from controlling one axis in relation to another axis that is not really fixed in space?
RE: Runout with MMC/MMB on DRF? No. Profile with MMC/MMB on DRF? Yes
John-Paul Belanger
Certified Sr. GD&T Professional
Geometric Learning Systems
http://www.gdtseminars.com
RE: Runout with MMC/MMB on DRF? No. Profile with MMC/MMB on DRF? Yes
CH,
I think the same about concentricity, why do I not want to have the option of controlling an axis to an actual axis and not just an AME of a feature? I guess I should be German :) they seem to understand me.
RE: Runout with MMC/MMB on DRF? No. Profile with MMC/MMB on DRF? Yes
There isn’t much difference between two holes on top of each other and two holes side-by-side.
You probably wouldn’t apply runout to every counter-bored hole anyway
My problem is over-thinking. Too much of “devil’s advocate” play.
If somebody wants runout defined at MMB maybe there is some use for it, and we could learn something here... NOT.