Does Flatness or GD&T add to dimensional tolerance stacks? 2

[livloud]

I'm creating an RSS tolerance stack of an assembly and was told I have to include flatness callouts of each surface in my stack, whether it's on the drawing or not. I have never added flatness tolerance to my RSS tolerance stacks before. Is dimensional tolerance inclusive of any GD&T modifiers?

 

[weavedreamer]

Per ASME:
Flatness comes into play in with the "To or Thru Rule".
[ul]
[li]If the stack goes to a surface, the form of the surface must be accounted for in the stack.[/li]
[li]If the stack goes thru a surface, the form of the surface is automatically included in the limits of the dimension.[/li]
[/ul]

Think of two flat washers held together. If you can fit a feeler gage between them, you are checking surface to surface. Flatness would control the amount of gap.

If you set a micrometer to the outsides of the two washers, the flatness would already be included in the dimensional limits of the two thickness'.

 

[CheckerHater]

Are you operating in ISO or ASME world?

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