Thanks, but I believe its a common problem even with brand new units. I can understand a small amount of wobble, but enough to actually cause a chainring or spider to scrape the plastic housing is disappointing. The play appears to be coming from the main gear and shaft connection.
All parts are made to be within a certain tolerance (machining metal with precise, exact sameness from one piece to the next is virtually impossible because the machine tools wear down or move a miniscule amount). So let's say two parts have to fit together, and the machining causes both to be on the high side (slightly larger than 'perfection'); they will fit together very tightly, with no slop whatsoever. But if the opposite occurs and both parts are on the low side, there will be a lot of slop. On average, most parts will fall close to the middle, so when they are mounted against each other there will be a very small bit of room but not enough to really notice.
The amount of the tolerance (and the quality control) will depend on the company. Sometimes a part that's outside of spec won't be caught and tossed, and they'll ship it for assembly anyway. If both parts are on the high side, they won't even fit against each other. On the low side, yikes the slop! But chances are, both won't be out of tolerance on the low side, although one part could be.
I guess the question in your case is, does the slop allow so much wiggle that it binds or throws the chain? If not, then at worst it might cause sidebar wear on the chain at a somewhat faster rate than normal, but other than buying a replacement chain a little more often there's no downside for riding. You could always buy parts to rebuild the assembly, though, and hope you get some from a different batch that will fit more tightly.
My chain ring deflects less than a millimeter under pressure, and there's no detectable "wiggle" in the shaft area. I guess I got a tight set.
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