Reply by RussellAP

If you look at the link http://www.mastertoolrepair.com/images/RIDGID_parts_R4512_saw.pdf the problem sounds like it’s between parts number 52 and 63. Most likely an arbor bearing due to a bad bushing or shim letting some dust in there, or just a factory part problem. I’d call them and send the sound link in an email. They will likely send you some parts free.

-- Failure does not stop me, it makes me try harder..... because I'm crazy.