Trying to setup an ABC alignment. A and B are no problem. Tried constructing a circle through C holes but ‘math failed’. X and Z are constrained with A and B. Y is a problem. Any ideas?
Much better!
C is the bolt hole pattern center defined by the basic dimension R18.400. Construct a mid point of the bolt holes using the basic angle of 8.75°. Then construct a line from the center to that "B" point.
In theory, an iterative alignment can handle it, but I've never tried without a complete bolt pattern.
A few ways to handle it, some versions of PC-DMIS won't be able to handle all of these
1) make a midpoint and but a line between part center line (datum B) and your midpoint, call that C.
2) make 2 preliminary ABC alignments each rotated by 8.75 degrees, so that they're nominally the same. Construct a theoretical point for C within each preliminary alignment, make a centroid, and clock to that.
Datum B is not a legal datum. ASME Y14.5-2018 clearly states in Paragraph 6.3.2: "... The datum feature symbol shall not be applied to center lines, center planes, or axes."
This placement of the datum feature symbol does not clearly indicate whether the actual datum is the center of the holes, or a center plane derived of the angled planes.
