Sometimes split lines will allow you to form circular patterns and sometimes they give re-build errors.  I can't figure out why or what to do about it.  (First I had tried to use intersection with radial planes, since I already had them, but the split lines created that way wouldn't pattern.)  This time my work-around was to circular-pattern a radial line in a sketch and then to project that sketch onto the ring face that I wanted to split.  Even this is not straightforward, however, because it won't accept radials intersecting at the center -- I had to cut the inner parts of the lines off first.

All I can find in SW Help is the following cryptic comment under Split Lines:  "You can pattern split line features that were created using projected curves."  This suggests that the more useful forms of split lines, e.g., Intersection (say by a plane), won't pattern, but I'm not sure I'm not doing something else wrong.

Anybody really understand this issue? -- John Willett