True position

[[Cl...]]

I have a true position callout on a slot to A & B, A is a plane, and B is a cylinder with a cone at one end. The slot is measured on the cone (cross section) The customer is asking for diametric T/P (2x) Wouldn't this be position in Z only for #13 & Y only for #15?

I'm interpreting the 4.25 (section CC) as a set value, so to me I don't understand why they are calling diametric T/P? Am I missing something here?

[[To...]]

What does your customer say? Probably a rookie mistake.

[[Me...]]

We have seen this on many of our customer prints as well and when we have asked our customer if that is truly what they wanted (Z for one and Y for the other) they did say yes. I think it as Tom said is a mistake but I guess the customer is always right correct? lol

[[Cl...]]

Thanks for the input guy's. When I see something called out on a print I generally ASSume it is correct. I just have to get some clarification sometimes.

[[Jo...]]

I'm more in agreement with what Tom mentioned. Regardless of what's on the print, the diameter symbol just doesn't make sense here. It's probably a rookie mistake. Not only that, the dimensions only apply in that slice of the section view since it cuts across a tapered surface. Position is just wrong to use here anyway. The best thing this will do is control the location of that 2D slice and leave the rest of the feature uncontrolled. Of course a customer will say "Yes, that's what we really want." You don't expect them to say something like "No, we actually don't know what we're doing." do you? They don't even have an MMC modifier in the FCF so there is no BOUNDARY.

[[Da...]]

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I have seen similar on some of our drawings in the past.
Guys/girls who make drawings are people too and just like everyone they make a mistake sometimes. It is interesting how difficult it is for us cmm people to decide whether to approach them or not (even when they are inside the same company).

[[An...]]

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[[Cl...]]

Thanks for the detailed explanation Andreas, I agree.

I have never seen the addition of "BOUNDRY" on
true position call outs as shown here?

[[Da...]]

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OK, Andreas, good point. I'm thinking, would similar apply if the sides weren't round (in other words, if the section would be square)?

[[Jo...]]

See Fig 7-34 along with the related paragraphs. It's a nice explanation with pertinent graphics. You'll notice that there is only support for the boundary concept at MMC. This is because it doesn't make sense any other way. There is support for position at MMC, LMC, and RFS but when the boundary concept is talked about, it's only MMC. Besides the other things I've already mentioned, the fix for this print is either modify the position tolerance at MMC or drop the word BOUNDARY from the callout. The diameter symbol is also wrong. No amount of graphics and imagination makes it right. Your first post about this was correct, Clarke. Report deviation in X and deviation in Z. I think that's the closest you can come to doing right, despite the print.

[[Cl...]]

Thanks for the input everyone.

[[An...]]

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[[Br...]]

What's even more goofy about this is that even if they did have an MMC or LMC modifier, the "BOUNDARY" is identifying the shape of the tolerance zone. So to say "BOUNDARY" and have a cylindrical tolerance zone specified in the FCF, completely contradict themselves.(Not to mention it makes no sense to have a cylindrical tolerance zone on a non-cylindrical feature anyway.)

BTW, is Datum feature B really the shaft and cone combined, or just the shaft? Maybe I just misunderstood your explanation of the Datum features, but I'd be surprised if it were really both combined as a single datum feature.

[[An...]]

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[[Jo...]]

Andreas,

What is your attachment showing? Are you saying that the diameter symbol is okay just because you can make Calypso evaluate it?

[[Cl...]]

Andreas, why don't you work for NASA, or MIT?

Looks like your talent is being wasted on CMM programming.

I'd be willing to bet it's because you have a real passion for doing this kind of work.

[[An...]]

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[[Jo...]]

I agree with your last sentence wholeheartedly but it's not really relevant to the issue at hand.

I kind of agree with your second to last sentence in that the standard can't possibly include every scenario that could exist, however there should be support for most interpretations even if it's through an extension of principle. So my question to you is this:

If you were to be asked where your interpretation of this callout is supported in the standard, what would be your answer? How would you reconcile the use of a diameter symbol and a BOUNDARY in the same callout? I've already posted my answer in a previous post. Your answer should not be "Show me where it says I can't." because the standard is a book of how things should be done, not a list of what not to do.

As far as your other statements go, whether or not you can think of these things and whether or not Calypso can evaluate them has nothing to do with whether or not the callout is compliant with the standard.

Respectfully (and I mean this),

John

[[Cl...]]

Andreas, are you stating that if you can prove your
method/theory to be true using Excel, then Calypso
should be able to do the same? Or did I misunderstand?

[[An...]]

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[[An...]]

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[[Br...]]

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ASME Y14.5-2009 para. 7.4.5:
Non Circular Features of Size
The fundamental principles of true position dimensioning
and positional tolerancing for circular features
of size, such as holes and bosses, apply also to noncircular
features of size, such as open-end slots, tabs, and
elongated holes. For such features of size, a positional
tolerance is used to locate the center plane established
by parallel surfaces of the feature of size. The tolerance
value represents a distance between two parallel planes.
The diameter symbol is omitted from the feature control
frame. See Figs. 7-30 and 7-31.

John, I know the point you are trying to make is that the standard isn't a rule book of what not to do,(and I totally agree) but in this specific case, it explicitly says it right there that you don't use the diameter symbol.

Note: Y14.5-1994 says the same thing word for word in para 5.10. I'm saying this because the drawing probably references the '94 standard due to the "BOUNDARY" statement.

[[Jo...]]

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How do you know it's an in house standard?

Well, if we are to the point where are just ignoring the standard then I guess I'm out of arguments.