Brian Lawson wrote:

Hey Wes,,

If threading fully to a shoulder is absolutely necessary, then
sometimes it is possible to add the shoulder later by some means.
Depending on the "meat" forming the shoulder, it is possible to do a
trepanning cut that allows the thread to actually go BEYOND the
shoulder face.

I'm considering adding a ring against the shoulder to get full length
engagement of threads. I'm still practicing my ID / OD threading skills
since I do not want to damage the article I'm trying to fix.

Wes