Self centering idler bearing for Y-axis belt.

I did not like trying to make the belt run absolutely straight on the Y-idler. Using little pieces of paper on a steel printer just seemed wrong!
This made me think of old fashioned "crowned pullies".

They are "crowned", higher in the middle, and that makes the belt stay centered.

For a nice description, look here:
http://woodgears.ca/bandsaw/crowned_pulleys.html

I belt sanded the bearing, to make a "crowned bearing" to use as an idler.
You have to be careful, but once it us done