I have an Advance cross slide rotary, and it does have its uses,(and yeah it's heavy...300ish pounds). There are way easier and faster methods to do this job. A chuck in a dividing head or an indexing head would be the way I'd go. The drawing appears to show that this is an assembly and there are multiple pieces, is that right?
If you don't have an indexer or dividing head you can use this table but there's no reason the table and vise need to be fully centered for a hole pattern. Use the cross slides to set the part zero (while rotating the table) with an indicator mounted on any solid part of the machine, then sweep the part with the spindle rotation (indicator mounted in spindle) to zero the spindle on center.
Calculate the hole offset to the first hole and move the milling machine table (not the rotary slide) to that location. Drill your first hole, then rotate the rotary table the correct number of degrees to the next hole, etc.
Appreciate the info. I'll give it a try very soon! Busy week!