This hole is initially aligned as one of my primary datums (A, B, C), but its unclear to me how I can measure it against UVW to make THAT my C datum and then use it to measure it again against itself?
I understand this is probably 101, but I'm just not processing it.
well, just a guess, but you measure & report the 'width' (direction shown) to UVW, that 'width' is then the "C" datum, then the 'length' of the hole is reported to ABC.
Yeah, it is a round hole, so no width or length, but lacking better terms, those are what I used.
I guess you could:
-Scan the hole
-Use variables to assign high points at the X+, X-, Y+, and Y-
-Make widths out of the points
-Call the "X Width" your "Datum -C-"
-Create alignment as needed
-Dimension accordingly
Looks to me like it's a diameter dimensioned from UVW first (maybe a cast datum alignment or similar?) Then you set up your ABC alignment as your main machined datums.
It two position callouts with planar tolerance zones (there is no Ø symbol preceding the 0.25 or 0.75 tolerance), relative to two different datum reference frames. One planar zone is orientated vertically to ABC and the other is orientated horizontally to UVW. Just measure the hole as a cylinder, create the respective UVW and ABC alignments and report the position of the hole relative to each one. If you're using legacy dimensioning then you will need to report the relevant axis (X,Y or Z depending on how you are aligned), if you are using XactMeasure (FCF dimensioning) you will need to set the planar zone orientation.
Not if you only select a single axis for the legacy position or remove the Ø symbol from the FCF (XactMeasure / Geometric Tolerance) and select the planar zone orientation.