I did not bore the roller bearing hole on the lathe.
The shaft surface that the roller bearing rides on is smooth (polished) with threads on the ends only.
The lathe I bought is the Shop Fox mini metal lathe from Northern Tools ($600).
It was a bit more than I wanted to invest in this project, but I hope I can use it for other things. I'm going to make a few of these (at least) to try to help lessen the wallet dent.
I'll have 3 shifters ready to ship next Friday if anyone wants one. I think
$135 shipped in the US is probably the lowest I can go. I'm not looking to turn a profit, so if that seems high, let me know.