There is a very loud vibration or nocking while the saw is running.

Hello,

My dad has an old Rockwell cabinet table saw in his shop. It is a great saw except for the fact that it is extremely loud while it is running. It sounds like a washing machine on spin cycle with a brick in it. My dad told me that “that is what old saws sound like” after I told him that the cabinet saws in my old high school’s wood shop hummed quietly while running (they were much newer than his though). I was curious and I removed the table and examined the mechanism and found that the arbor bearings looked damaged. We had the bearings replaced and re-pressed into the arbor. Unfortunately the sound persisted after this repair. I read a good tip to run it without the belt on to see if it was a problem with the motor balance or something, when I am home next I will try that. I did notice as I was putting it back together the first time that when I spun the motor with the belt on (I pulled on the belt) I could feel a clunk or nock with every full rotation (approximately). My dad seemed to think that it was just noisy belts and getting a set of noise reducing belts would fix the noise. Im not convinced since I can hear the saw from inside the house when it is running in the basement of a garage that is separate from the house by 25ft. I will probably inherit this saw in the future and I would like to preserve this solid machine. 

I dont live at home anymore so I dont have model numbers or motor specs but 2.5hp sounds familiar. I think it may be a “Unisaw”. Do any of these problems ring a bell? I would be satisfied with “that is what old saws sound like” if that is truly the case.

Thanks for any input