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GD&T question - Position of that slot

pab39
Hey,

I have to help some engineer for his drawings, and i wonder about something.
Here it is:

Admitting i have that part (picture), and the important thing on it is that the slot has to be well centered related to the Ø15 hole.
As the slot is already dimensionned with profile on the drawing, my fist idea would be to add A reference on the hole, and add A datum into the Profile (picture2)
But would this work ? and is this OK related to ASME ?

Someone proposed to add symetry to locate the slot (pisture3) but i guess this does the exact same thing. and btw, is it possible to dimension symetry related to an axis ?

How would you dimension that ?
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  • In this case, I would create the FCF with B|A instead of A|B.
    If B is the primary, then A becomes the projection of all hits of the cylinder on a plane perp to B, to construct a max inscribed circle.
    If A is the primary, then you have to search a mid plane containing the cylinder axis and minimizing the tangent external width (Maybe PC-DMIS can do it, but seems to be complicated ?)
    IMO
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  • In this case, I would create the FCF with B|A instead of A|B.
    If B is the primary, then A becomes the projection of all hits of the cylinder on a plane perp to B, to construct a max inscribed circle.
    If A is the primary, then you have to search a mid plane containing the cylinder axis and minimizing the tangent external width (Maybe PC-DMIS can do it, but seems to be complicated ?)
    IMO
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  • in reply to JEFMAN
    PC-Dmis (using the geometric tolerance command) would handle A|B fine. Cylinder A would constrain 4 degrees of freedom (2 rotation and 2 translation), plane B would constrain the third rotational degree of freedom, leaving translation along the axis of A unconstrained. Depending on the design intent, additional GD&T controls may be required - for example a tertiary datum to constrain translation along the axis of A and a perpendicularity of the slot walls to the uppermost surface (or parallelism to B).
  • in reply to JEFMAN
    Thanks, yeah that's also how i see it. Anyway the part showed is only a representation, the real part is a bit more complex and the slot design too, the engineer has dimensionned the slot position on the A axis with a tight linear dimension, i think we will let it like this for clarity.
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