The Howa / Vanguard has a metric barrel tenon thread that my lathe won't cut unless I leave the threading lever engaged. I can set the levers and dials for many metric threads, but once started, have to complete the thread without ever disengaging the carriage. I think that any lathe with an inch pattern leadscrew has this limitation.
I don't have the skill and agility to do this under power, so I have to put the spindle in neutral and turn the chuck by hand forward and reverse to avoid a wreck. The leadscrew transmission is in constant mesh with the spindle whether the motor is engaged or not, so in neutral, it saves me from having to turn the motor (and drive belts).
There are craftsmen out there that can do this at powered spindle speeds, but I'm not one of them.
Bottom line, it's a very slow process, and I'm old, fat, and lazy, and don't want to do it unless I have to.
Good question.
Tom
