Knocking Powermatic 66

I have a Powermatic 66 I bought new in 98. There seems to be a vibration or knocking sound that started a couple months ago. After finally getting around to investigating the sound the Sheave arbor (fan belt pulley) as they call it was lose. I removed the pulley did not see any damage remove the arbor assembly bearings seem alright. So I reassembled everything turned it on everything sounded fine once I installed the blade the sound returned , removing the blade did not help the sound was still there. I did the whole procedure twice both times the saw sounded fine until I installed the blade I did use another blade for the second test. I did run the motor each time by itself no belts it sounds fine. The arbor and bearing assembly fell fine but all I can think is that's were the problem is. So at this point I'm thinking replacing the Sheave as a starting point it was lose for quiet awhile. If anybody has any suggestion of what else might be wrong I'd appreciate it?
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Sac Dave wrote:

Is there a shear key associated with the sheave? If the sheave was loose the key may be worn and the problem is showing up only with the extra force required to overcome the inertia on spin up with the blade installed.
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Jack Novak
Buffalo, NY - USA
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That's a good point I'll try the key first it did slip in place pretty easy maybe to easy. Thanks
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If there are set screws in any of your pulleys, make sure that they are all *tight*. I had a problem where the thunk wouldn't happen unless the belt was on. And I couldn't wiggle the pulley on the shaft.
Just a suggestion.
D'ohBoy
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Be aware that you may have 2 set screws stacked on top of on another. The second one is to keep the first from vibrating loose. I'm sure you can figure out what to do from here. Art
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The fist time I took it apart the sheave set screw was lose. I even used lock-tight on it the second time .
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