After watching Mary fiddle with the shrunken presser foot screw, I tapered the tip as a guide into the hole:
A hint-and-tip (which I cannot, alas, find again) suggested making bushings to simplify trimming screws in the lathe. A rim on the bushing aligns it with the front of the jaws, the screw threads into the central hole with a jam nut locking it in place, then you can turn / shape / file the end of the screw just beyond bushing with great support and a total lack of drama.
For the moment, I just aligned the screw in the tailstock drill chuck, crunched the three-jaw spindle chuck on the screw head, backed off the tailstock, took unsupported sissy cuts, and it was all good:
Gotta make those bushings!
The Smell of Molten Projects in the Morning 
I did something like that for all-thread rod that needed to be turned into leadscrews. I took a length of 1″ brass hex stock, punched one facet to give me theta repeatability, faced, drilled and tapped full length. One bushing is 1/2″, while the other is 3/8″. I didn’t care about repeatability in the X direction&*, but by using the punch mark and hex stock, I could minimize the runout and still use a 3-jaw chuck.
When I needed 3/4″ jack screws, I used full-sized nuts to hold them. Worked all right and I didn’t have to worry about damaging the threads.
(*) A quick and dirty way to keep X registration would use a washer between the hex and the jam nut. Permanant solutions are left for the student..