Jack I have several straight, tapered and adjustable reamers that would fit the bill perfectly I use then for fixing shotguns chambering rifles and so forth.
I think you could find a used 9/16 reamer from a machine shop pretty cheap as they would have no use for it anymore.
Drill the hole a wee bit smaller and use the reamer to finish.
Probably over kill.
I cant be a smart ----- with out some help.
Worth