[Photon]

What's a good way to hold this bearing in place?
Thought about glue, but I guess that will prevent me from replacing the bearing when needed.

[pminmo]

How about a small piece of dowel rod the same diameter as the hole with an appropriate sized hole in the middle?

[Photon]

It may work.
What would hold the dowel ring (dowel rod slice with a hole in the middle) in place?
Should it be made to fit the thickness of the MDF and then held in place by some piece of wood bolted to the MDF board?
Is there a more elegant solution?

[kong]

Or if you can move the bearing, you could make a metal plate to lock the bearing in place, like over here:
http://www.buildyouridea.com/cnc/tk-...6/phase_6.html

[HuFlungDung]

You could look for some bearing flangettes. This is a pair of stamped metal pieces designed to hold a spherically shaped OD bearing. This is very common on agricultural equipment. Cheap too...not as cheap as a hole in a piece of MDF, though

To mount these, you simple drill a couple of bolt holes for mounting bolts that go through the flangettes. It is kind of a self aligning face mount bearing fixture.

[Hobbiest]

If you are using MDF for your frame, bore into it with a forstner bit the correct OD of the bearing. If not using MDF, either bore in to your material a suitable amount, or make up a mounting block out of MDF or UHMW. Get a fender washer with a suitable hole size so that it won't constrict the motion of the bearing. Drill two holes on the flange, and secure it to the MDF base with screws.

[pminmo]

Use a fender washer (big washer available at hardware stores)and a glue the dowel to the washer. See pic.