Orientation of DRF not aligned with a datum feature

[Woosang]

Hi all,
I need your advise.
Please have a look at Y14.5 - 2009 Fig. 4-46. I will not talk about the customized DRF so let’s modify some features.
- Datum feature B is not a square cutout, it is a round hole with perpendicularity control w.r.t. Datum A
- Datum feature C is same as original feature, except that its DRF was customized.
- 3X hole is tagged with two single segment position control.
- DRF identification is same as original figure. Design intent requires one axis of DRF to be offset from datum feature C.

Case 1: 3X hole position upper segment is TP|∅0.5|A|B|C and lower segment is: TP|∅0.2|A|B.
Now what would the lower segment tolerance zone look like? Zone H or Zone V?
Case 2: Upper segment is same as 1st case and lower segment is: TP|∅0.2|A|C.
Now what would the lower segment tolerance zone look like? Zone H or Zone V?

(again, DRF's are not customized)

 

[3DDave]

Since an axis doesn't control rotation about the axis it should control the position in a radial direction from (case1) or [C] (case2).

 

[Woosang]

3DDave,
thank you for your reply.

My original thought was if we need the tolerance zone to be in horizontal or vertical direction, datum features should be aligned that way or we need a planar or center plane datum aligned that way.

However, I searched Y14.5 (1994, 2009, and 2018) to see by any chance an axis or a plane of the DRF not aligned with the datum feature could control the orientation of the tolerance zone - paragraphs like, inclined datum feature, datum plane from the datum targets on stepped surface, datum established from complex features, etc - but haven’t succeeded yet.

 

[chez311]

Woosang,

Just to build off what 3DDave said, the answer is neither. "Zone H" assumes [x] is unconstrained, "Zone V" assumes [y] is unconstrained. Neither of these is the case in your example, both B and C in your hypothetical case constrain BOTH [x,y], only [w] is left unconstrained. Your tolerance zone would move in an arc in the rotational [w] direction centered around B and C for cases 1 and 2 respectively.

 

[Woosang]

chez311,

Yes, you are right. Because what constrains the tolerance zone is the actual DATUM FEATURE, not x, y axis of DRF defined.
But I am looking for if there is any logic allowed by Y14.5 that imaginary axis of DRF associated with (like, offset from) datum features or portion of datum features can constrain the tolerance zone.
Please see my previous post. Do you think I can succeed?

 

[chez311]

But I am looking for if there is any logic allowed by Y14.5 that imaginary axis of DRF associated with (like, offset from) datum features or portion of datum features can constrain the tolerance zone

The derived axis is as you said - imaginary or theoretical. It does not constrain any DOF, your datum feature combined with its associated simulator does. It doesn't matter if you assumed a derived axis, or any theoretical feature for that matter - whether it be a point, line/axis, or plane, to coincide/be concentric with or be offset any arbitrary distance from your datum feature - it does not and cannot constrain any DOF. DOF are only constrained by the interaction between your physical datum feature and simulator/TGC.