I have a Powermatic III that makes a rumbling noise when I turn it off. It sounds like a bearing or bushing, and the blade is wobbling as it slows down. It has enlarged the zero clearance plate from the movement. Any thoughts or suggestions would be appreciated. – Ed Sapp
Tim Inman: I’ll bet dollars to doughnuts you have a loose belt pulley in there somewhere. I have often experienced this over the years, working and teaching in many different shops. The little set screws that lock the pulleys down tight to the shafts work their way out, and let the pulleys wobble. It only “growls” when the machine is winding down to stop and the power source shifts from the motor driving the blade backwards, so the flywheel momentum of the blade begins to drive the motor. A new “link” type V-belt will really help quiet vibration, too.
Chris Marshall: I suspect Tim is right here about a loose pulley, in terms of the noise that develops when the machine slows down. But, you might also have a worn bearing or bearings in the arbor assembly if the blade is really wobbling enough to notice the effect — the arbor shaft should spin true even if the pulleys are loose. That’s not a good sign. Tighten the pulleys first and try a link belt. If the blade still wobbles, it might be time for new arbor bearings.