How to remove angle grinder gear

My $9, much used, HF 4-1/2" angle grinder has a bad bearing. To replace it I need to remove the spur gear on the end of the motor shaft. The
gear is threaded on, but has some sort of retainer, I think. It kind of looks like a key, but it's not: the shaft doesn't have a keyway & the shaft is threaded.
http://home.comcast.net/~bobengelhardt/GrinderGear.jpg
I haven't seen this before - could it be a wedge that was driven in to lock it? If so, I suppose there's no way in hell that I'm going to get it out (no access in the back and no EDM).
I hope I can fix it 'cause otherwise it's a perfectly good grinder & why should I spend $9 on another one? Although I haven't seen them for $9 in quite a while. $15 now, I think.
Bob
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Wait - it isn't threaded & it is keyed. A woodruff key, so the slot doesn't extend to the end. It pulled off & I'm all set.
As you were, Bob
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