5/8"-16 Threaded Adapter?

[MONT204]

Been a lurker for some time but now have a question for all.
I need an thread adapter 1/2"-20 female by 5/8"-16 male approximately 3/4" long.
Yes it is in fact 5/8"-16 thread that is used on most electric drills.
looking to be able to put a special drill chuck that only comes in 5/8"-16 on a drill with a 1/2"-20 shaft.
I would be willing to pay to have a few made if possible.
Thanks for looking.

 

[rwm]

Looking at the thread chart the minor axis of the 5/8-16 only leaves about 0.025" of metal before you run into the 1/2-20. Unless you can accept lengthening the distance from the drill to the chuck and threading each end of a short bar. Also, what it the tolerance for runout? All of this will introduce error.
Robert