Hi folks. Here's the end of the story, and some of you will be aghast at what I've done.
Remember that the goal of this was to keep the expense to a minimum. As Jack says, "Go with what you've got." This little toy (though all of what we do are toys) will only run on air and then perhaps not more than a few dozen times.
I found a spiral flute reamer on Ebay for $20, but considering that in some 35 years of, as my sig line says, turning perfectly good metal into bits of useless scrap, I've never needed such a reamer and more than likely will never need one again. So that is set aside.
The steel bearing ball is a great idea, and I found a package of 10 of them on Ebay for about $6 and change. But, again, I'd have to spend six bucks and I'd end up with ten bearing balls that would just sit in my scrap — uh — parts — department until my heirs end up stuck with all the detritus in my shop. And the idea of just tossing them after I'm done with this is heresy.
The idea of burnishing it with a ball bearing is a good one but I was afraid of trying that because the forces I suspect would be required would not be tolerable by my Atlas lathe (a.k.a. The Flexible Flyer).
So I woke up about half past six the other day and while I was lying in bed waiting for the clock to chime seven (I'm retired. I do not get up early.) it dawned on me. If I made up a doohickey sort of like a boring bar, but with a spot on the end that would hold some abrasive paper, I could run that into the bore sort of like a one-legged brake cylinder hone. (You young'uns have probably never seen a brake cylinder hone....)
So below are the pix. The toolmarks from boring all went away and it all worked out fine. The cylinder did end up with a very slight taper, but only .004 (which is only .002 per wall) which is of no consequence in this case. (If it was something Really Important, I think I would have bought the reamer.)
Greg Lewis, Prop.
Eyeball Engineering — Home of the dull toolbit.
Our motto: "That looks about right."
Celebrating 35 years of turning perfectly good metal into bits of useless scrap.