How would you round out a 5 sided object?

[drrags]

I tore the guts out of an A/C compressor with 5/10 pistons. I want to round out the material around the bearing for some future use, but mostly, this is an exercise and learning opportunity.
* My lathe jaws are too large to fit in the hole
* 5 sides so I can't figure out how to fit it in my 4-jaw
* I can't figure out how to mount it in my rotary table and get it centered
So far, this is a fun puzzle, but I'm about to clamp the device in a vice and spin it with a flap disc on my angle grinder, but I'm not a neanderthal, or at least I don't want to be.
How would you turn this star-shape into a round shape? Pictured is one that I've been working on by milling the sides, one at a time, around and around, and the other, I haven't started on yet.

 

[Lo-Fi]

I'd press out the bearing and make an arbor. No shame in lopping off the excess caveman style first, though!

 

[mmcmdl]

Turn a " spud " down on your lathe to the ID diameter . Put a thread into it and bolt your part on .

 

[SLK001]

+1 on pressing out the bearing and making an arbor to fit. That's how it would be done in the industry.

 

[FOMOGO]

I would summon the power of the pentagram, but then I have a black magic woman. Mike

 

[T Bredehoft]

Yes, an arbor will do nicely. If not removing the bearings, put a nut in your three jaw and mount the piece on a bolt (turned to fit the bearing) and tighten the bejesus out of it.

 

[drrags]

Got it done. When I went to pull the bearing, I realized that the blind bearing puller itself would make a reasonable arbor (or whatever it's called). Not concentric, but good enough that I can now find center and fix to the table.
Thanks for all the ideas!