The bench arbor I had allowed me to have the belt go straight down.
This was helpful because the motor I used just hung on a hinge to
keep the tension on the belt.

My old one (it was made by Millers Falls) chattered. I discovered if I
pushed with a finger on the end of the spindle the chatter went away so
I diagnosed end play. I tore down the spindle and made up a shim. Ran
quiet. Couple of months later it started again. I gave up chasing that
chatter and just lived with it. I never used mine with a grinding wheel,
just a buffing wheel on one side and a rock polishing drum sander about
6" in diameter on the other. That was one awesome polishing setup. That
drum grabbed a carpet knife I was sharpening (the hook kind) and flung it
right in my face. I was wearing a face shield and it took the whole hit.
It destroyed the face shield but I was fine (although a little freaked out).
I hung that face shield in my shop for a few years to make sure my kids
got the point. And I never tried to sharpen a hook knife again.

GWE