Thanks for the suggestions.

One issue I have with the coast method is that even using the slowest
rpm (70), and dry running to figure amount of drift (1/2" in this
case), it may not consistently coast that 1/2 an inch. With only a
small relief area being allowed, this runs a good chance of damaging
the part and tool. The hand crank method suggested by others seems
like viable option given the short distance required to be threaded.

Will check tonight on the reliability of consistent drift or try and
make a manual crank for the outboard section.

These responses are greatly appreciated.

Doug