Parallelism + Square on the slot? 2

[JimmyOon]

Parallelism or Flatness + Square
How does it works here?
Does it means each "Square" block needs to control at 25.4? Or every "Square" block is 25.4 and need controlled at 0.03 Parallelism/Flatness?

Thanks.

 

[Burunduk]

The callout as it is does not conform to any standard, therefore only guessing is possible. There must be datum references for parallelism, or orientation controls in general. The first segment could attempt to specify parallelism of one surface to the other. According to old versions of an ISO standard, one leader had to end with a triangle to specify the datum feature. The second one could be an incorrect attempt to state a requirement on unit area basis (each 25.4 X 25.4 area needs to be within the smaller tolerance). The square area specification needs to be in the tolerance compartment, after the tolerance value. Not in the datum reference compartment.

For flatness, the closest thing documented in the ASME standard is this:

 

[JimmyOon]

@Burunduk
Thanks for your feedback.
I think, it should be Flatness, the total length slot is 250, so each every "Square Block" is 25x25 and with Flatness of 0.03?

 

[Burunduk]

I think each sample area of 25 X 25 must be within 0.03 would be the most probable interpretation of what they tried to communicate. I recommend clarifying it with the source of the drawing though.

 

[3DDave]

JimmyOon,

I expect profile of surface is the correct choice as it would link the two surfaces and not require a datum reference.

Suggest a profile of surface tolerance to the originator of the requirement. If a datum reference would help, then profile of surface can also be used to locate and orient these surfaces to that reference, a task which flatness cannot do.

One can also use the composite/multiple segment control with the area modifier for the profile of surface tolerance.

 

[DanStro]

I agree with 3DDave, I think profile of a surface is the way to go.

Here is a link that is kind of similar to your case, minus the per area:

https://www.tec-ease.com/gdt-tips-view.php?q=143