My older flat wheel wire brush from Menards was vibrating rather
wildly on my 1/2 HP motor. So a few days ago I asked a bunch of
questions about wire brushing, hoping to improve my situation.

Here's the outcome. I bought a 8" fine wire bruch from McMaster, item
4840A48. Also bought one extra motor arbor adaptor.

After replacing the previous brush and previous adapter with both new
brush and a new adapter, the difference is huge. The motor no longer
vibrates, the noise is gone, and it is all smooth and quiet.

I believe that 1/2 horsepower is fine for this fine bristle brush,
because the manual says do not press too much on it when brushing. If
I do not press too hard, then the motor keeps up with speed just
fine. This is a 50 year old Peerless motor that cost me just $2 (IIRC)
and if I can use it, I will be happy.

What I use this brush for, is I clean various gunky or slightly rusty
things.

i