Following the discussion in viewtopic.php?f=3&t=6307 I tried making a polar pattern around a datum line in the newly-updated assembly branch. It *almost* worked: during the polar pattern dialog the proper results are displayed, but confirming the dialog throws an error and the polar pattern feature cannot be created. It turns out that the wrong object was stored as the axis. https://github.com/timoore/FreeCAD_sf_m ... 616301553e fixes this bug; please pull and apply to jriegel/dev-assembly.
With this patch I can model the cylinder holes in my crankcase as a polar pattern rotated around the X-axis without creating any helper solid geometry, which I think is great!