This seems like mana from heaven (or moonshine from down below)...
I've struggled with my Voyager's crank from the day I purchased it. I managed to get some respite from this foreign Jet arm I picked up somewhere, I tried to fabricate a connection that had me thinking what was I thinking, Your solution seems the best kid on the block... though being an imperial ignoramus and bamboozled with all your fractional quotes, is this socket, the 3/8" you were referring to? Being imperial, would it object to a metric (6mm) tap?
If your first cut is too short... Take the second cut from the longer end... LBD