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Flatness w/ Perpedicularity and parallelism redundant?

Flatness w/ Perpedicularity and parallelism redundant?

Flatness w/ Perpedicularity and parallelism redundant?

(OP)
Hello all,

If I have a cylindrical part with a hole bored through the middle (the shaft spacer sleeve again), does it make sense to spec a flatness tolerance on one face (datum face) and a parallelism tolerance on the opposite face with respect to the first surface if there is also a perpendicularity callout on the center bore, or is the flatness in this case redundant? The length tolerance is 0.4mm total, and i spec'd the flatness and parallelism at 0.1mm each. Seems the perpendicularity tolerance would limit the flatness of the first (datum) surface if the tolerance was tight enough. Am i right about this? Again, working to ISO.

Thanks!

RE: Flatness w/ Perpedicularity and parallelism redundant?

Control of the actual datum feature is not applied, simply by its use as a datum, so it is not redundant.
Frank

RE: Flatness w/ Perpedicularity and parallelism redundant?

Keeping it short, perpendicularity on the bore has nothing to do with flatness of primary planar datum feature. No matter whether it is ISO or ASME.

RE: Flatness w/ Perpedicularity and parallelism redundant?

(OP)
Guys, thanks for the replies.

I realized that in all of the examples I was thinking of, I was imagining the surface with the flatness control to be inclined, and I was thinking of that inclination as the surface not being flat (although it actually was). After drawing a few simple pictures with wavy surfaces that still represented good parts this made sense.

Thanks!

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