The microwave at our coworking space was missing the plastic part between the motor shaft and the knurls of the glass tray.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!