This page talks about my failed anchor bolt mod to my stir crazy.
I replaced the plastic shaft threads with a 1/4″ anchor bolt. There isn’t a lot of “meat” for the wood threads to bite into so a generous amount of JB Weld secures them in.
Another hobby of mine is woodturning so it was fairly simple to drill a centered hole into the plastic piece, I gripped it in my #1 jaws and drilled the hole using the tailstock. I think that a person with a drill press and vise could do an adequate job on this, it’s not a high-speed part so some wobble is OK.
But eventually the plastic shaft melted because while pre-heating the oven I got distracted and the base overheated.