Captured (blind) bearing holder

There are plenty of 608 bearing holders up here already. Why another one?

* Glued-on inner-race plug ensures the shaft doesn't touch the backing and cause drag.
* Strain relief on the press-fit means no cracking due to minor dimensional inaccuracies.
* Inner lip on the backing touches only the outer race, making it possible to properly pre-load the bearing.

I'm using this with a cone hub for a spool holder.