MMC Position of Non-Feature of Size

[[To...]]

Any way to do this per any standard? Maybe with a formula?

Is there a profile option that would take its place?

Screenshot 2022-11-15 132317.jpg

[[Jo...]]

I'm not understanding which feature you want to control. If you wish to control the orientation with the Datum precedence, but want to use the Distance from the end....ASME allows custom FCF for that.

Or is the question, How to control the end from the Position ??

[[Th...]]

This doesn't make sense to me as dimensioned. Is the intent to control the location of the end plane relative to the center axis of the C feature? Would it make more sense to use an unequally disposed or unilateral profile to A|C|B then?

[[Ch...]]

I would create theoretical plane with X value (PCM) that is same as circle center - this along with the end plane, you should be able to create a symmetry plane which will allow MMC (watch ID/OD switch).

Symmetry plane might not like the theoretical plane created, if not; I would make a Theo symmetry plane then using the measured features.

Good luck !

[[ni...]]

Hi,

for me the draft is not-ok.
for large tolerance and with most of our customers
I 'll program both :
-localisation of the plan without maximum matiere but with the draft's referential
-localisation of the cylinder from the plan with orientation on B-C and X=0 on the plan
if the two are good the part is good for me.

in case of small tolerance or a "%#@" customer or if one of the two mesure is bad, i'll ask customer about this willing.

Slts

[[To...]]

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Sorry about that. It appears they are trying to control the location of the plane feature on the end. The dimension is not BASIC either.

[[To...]]

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You're on the right track as an alternative to the position callout. Can you be more specific with the correct profile usage?

[[Jo...]]

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I'm thinking this is probably the design intent. I still don't understand not having a Basic dimension, at least daisy chained to Datum structure. A Custom DRF ASME Y14.5-2018 7.23(figure 7.57) would be more flexible. Implementation is another challenge. If you use an alignment, and profile as suggested you can pick and choose origin. Pick the appropriate DRF and swap the position symbol for profile ? It is not a f.o.s and has a total width zone...

[[To...]]

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Using MIL standard, not ASME or ISO, so the rules are different, plus we all know how many times engineers put stuff on drawings that don't make sense...lol

Below is a much closer representation of the their drawing. I was trying to keep my original sketch more simple....

Screenshot 2022-11-16 111724.jpg

[[Th...]]

So this looks to me like it's a position tolerance applied to a distance, meaning it's tolerancing a center plane between the real plane in the center and a parallel theoretical one that passes through the center axis of the C feature. Is that an accurate view?

[[To...]]

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I think it was an attempt to say, if you make the distance greater (the plane has less material), you get more tolerance.

[[Ro...]]

Hi Tom,
You can't get more tolerance. It just ends up being a +/- dimension to some orientation. The tolerance is already defined by the linear callout. If you added bonus you'd violate that tolerance.

I get these on occasion and almost always end up converting them to profile and submitting a drawing change request.

[[Th...]]

I know. I was trying to figure out the design intent, but no matter how long I look at it I can't figure it out well enough to make suggestions.

[[To...]]

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My original post also inquired about profile alternatives but I haven't seen a suitable application.