Flatness and paralelism

[roberto1brazil]

Hello all
We have a part with two flanges. One of them is our datum X – see sketch – with a flatness of 0,02 mm max. The other opposite flange (surface) has the following indication: flatness of 0,02 and parallelism of 0,02 mm as showed in the sketch. My question is: Is it necessary to show the flatness of 0,02 mm in the flange opposite to “X”? In my mind just the parallelism of 0,02 mm would be enough. Is my supposition correct? Thanks for any help that you can give me.
Roberto

 

[pmarc]

Yes, you are right.
Flatness is indirectly controlled by parallelism callout. So it only makes sense if its value is smaller than parallelism tolerance, otherwise is redundant.

 

[GordyRC]

The parallel control reads like this. Al elements of the considered feature (surface) must lie within a tolerance zone having a width of 0,02 which is parallel to datum X. In this case the tolerance zone has a width of 0,02, so by definition flatness is controlled since all elements must lie within the 0,02 wide tolerance zone. Any additional flatness control must be less than the parallel requirement.

 

[roberto1brazil]

Thanks pmarc and GordyRC for the answers and explanations.
Regards
Roberto