This is the second revision, didn't bring calipers to the office so just kind of eyeballed and iterated. There's still room for improvement: shaft outer diameter leaves it rubbing on the floor hole, and I didn't measure the correct inner dimensions either.

After test fitting I couldn't really pry it back off easily for adjustments, but the glass turns and we're no longer getting nuclear char spots in our leftovers, so I'll take it!