yosemitebill

I recently acquired a direct-drive Craftsman 315.218050 table saw which works, but the motor shaft assembly rattles loudly when it spins down. My guess is that a shaft bearing is going out, and I want to replace it before it does more damage. I found that I can get an arbor shaft assembly for a reasonable price, but I don't know just how to install it. I have separated the motor from the cast (aluminum?) gearbox but don't know how to open it up to get to the shaft assembly inside. Here are two photos: As you can see from my photos, there is a retaining ring holding the shaft in place. It has a set of bump-outs on both "ends." I'm guessing that's there to allow a tool to unscrew it. But I tried to turn this piece counterclockwise several times and it's not moving in or out, as it would if the housing were threaded. Anybody have an idea how to get this open? Many thanks!