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  1. Sem_D220

    Phantom line gages as datum "features"?

    Then I suppose there are no important differences. Thank you pylfrm. It is great to look at familiar things differently from time to time.
  2. Sem_D220

    Validity

    I have an issue with the implied meaning of "not in the same way". I say that in the context of DOF constraints, different ways of constraining a DOF lead to an identical final result - not in terms of the consequential tolerance zones established, but in terms of what a DOF constraint is by...
  3. Sem_D220

    Validity

    I suppose that by the same interpretation, datum feature simulator of datum feature A in fig. 4-21 illustration (b) is involved (at the end result) in constraining the degree of freedom parallel to the A axis?
  4. Sem_D220

    Validity

    chez311, you probably missed the edited version of my opening statement which represents the idea better (sorry for not identifying the edit - but it was done pretty soon after the post): it says now: "It is not mandatory to start by constraining just v (or w) in order to finally constrain X...
  5. Sem_D220

    Validity

    Ok, I think I get it. pylfrm, chez311, It is not mandatory to start by constraining just v (or w) in order to finally constrain X "everywhere". Consider a simple case of 3 perpendicular planar datum features. A(primary), B(secondary), C(tertiary). XY plane is coincident with A. B perpendicular...
  6. Sem_D220

    Suppression of envelope - Thickness defined independently of shape of flexible part? (ASME Y14.5)

    greenimi, The OP showed in the first image that the part can be bent when not restrained. If this information is not provided and all you have is a drawing not showing the view with >= 1.005 limit in bent condition - how do you know a part is subjected to free state variation in the unrestrained...
  7. Sem_D220

    Validity

    This is why for fig. 4-9 I would say that once A, B and C are all involved - u and v are constrained by A B and C together. However, there are different opinions: Perhaps you missed the fact that my objection was regarding the involvement of the primary datum feature A in the constraint of w...
  8. Sem_D220

    Validity

    That can also be said about fig. 4-9: The set of constraints controlled by A is u, v, Z. The set of constraints controlled by B and C: when only B is involved - X, Y, only through the axis of B, once C is involved - X and Y everywhere, w. None of these are controlled by A - at least when only A...
  9. Sem_D220

    Phantom line gages as datum "features"?

    Nice to kbow know I'm on the right track with this. Could you tell what the quibbles regarding the "virtual fixture" be about?
  10. Sem_D220

    Validity

    pylfrm, can I conclude that since datum feature simulator A for the spherical component of the bearing doesn't impose a basic location or orientation relationship on the movable datum feature simulator B, it is not involved in the constraint of the degrees of freedom that start to become...
  11. Sem_D220

    Suppression of envelope - Thickness defined independently of shape of flexible part? (ASME Y14.5)

    "This is how the part should be allowed to look like this when not constrained" and the embedded image that follows imply Free State Variation. That means (b) in greenimi's quote is in force. It doesn't have to do with industry/government standards. Edit: rephrased for clarity.
  12. Sem_D220

    Validity

    chez311, I can not say that I fully grasp the concept you described it, but it is interesting. I suppose it will be up to pylfrm to confirm or deny. I guess I will just cling to my own perception which is that constraints of degrees of freedom as meant by the standard are such that each type of...
  13. Sem_D220

    Is a MMB callout on the datum of a feature control frame for perpendicularity of a plane illegal?

    After re-reading the described design intent in Ev-36Xpro post from 26 Apr 19 14:52, I suggest considering: * B as the primary datum feature. * Qualifying datum feature A with position perpendicularity MMC referencing B - as suggested in the second drawing in the OP. * Controlling the dowel...
  14. Sem_D220

    Is a MMB callout on the datum of a feature control frame for perpendicularity of a plane illegal?

    It sure is. I meant |B|A(M)|. Thank you for the correction. In case Ev-36Xpro will want to know: There is a difference between |A(M)| and |A(M)|B| in the feature control frame for the pin. For |A(M)| the full gap between the produced bore A and the gage shaft can be utilized for play...
  15. Sem_D220

    Is a MMB callout on the datum of a feature control frame for perpendicularity of a plane illegal?

    Recommended or not, it doesn't take an "expert" to tell that |A(M)|B| might reject some parts that would be acceptable for |A(M)|. The rest is a matter of what suits the function best. Without delving into details I would probably just through a guess that |B(M)|A| might be a better choice...
  16. Sem_D220

    Is a MMB callout on the datum of a feature control frame for perpendicularity of a plane illegal?

    greenimi, thank you for the reference. I don't want to hijack this thread but I am tempted to ask - what part of those quotes made you conclude that a secondary planar datum feature theoretically perpendicular to a primary datum feature of size specified MMB does not influence the outcome of...
  17. Sem_D220

    Phantom line gages as datum "features"?

    pylfrm, I think I'm finally starting to understand your approach. I'd like to explain it with my own words - please tell me if I'm on the right path. The drawing and everything related to it includes only the basic geometry with selected features designated as datum features, the required basic...
  18. Sem_D220

    Validity

    pmarc, I was convinced by each of these statements separately when they were posted but trying to understand the meaning of them in conjunction with each other I can't help but find them contradicting. Y14.5 defines w rotation as rotation around Z axis of the datum reference frame, not about any...
  19. Sem_D220

    Validity

    That is true only as long as everyone agrees that w is rotation about any axis parallel to Z, u is rotation about any axis parallel to X, and v is rotation about any axis parallel to Y, just as translation at X direction is caused by translation vector applied anywhere parallel to X, etc...
  20. Sem_D220

    Is a MMB callout on the datum of a feature control frame for perpendicularity of a plane illegal?

    greenimi, take a look at ASME Y14.5-2009 fig. 4-21 illustration (c). Are you sure that B secondary "does nothing"?

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