I am surprised no one commented on my post.
What I was trying to get across, is you do not
need a screw to make a screw. A lathe carriage
can be driven by a rack and pinion, even a
chain and sprockets. Heck, I have seen some
very old lathes that had their carriage driven
by what looked like ship anchor chain. LOL
Even rope on a spool could serve to drive a
carriage if the rope were strong enough
and the cut was light enough.
You guys just seem to be fixated on the notion
that you need a screw to make a screw.
I have an example of that not being true
right here in my shop with my Hendey lathe.
So don't believe everything you know.
---Doozer
On my Hendey Tool and Gaugemaker's lathe
I can cut threads with the feed rod, driving
the carriage through the rack and pinion.
It cuts threads just fine, just reverse the
spindle to back up and don't open the clutch.
There is some math involved, I forget the difference
between the leadscrew and feedrod ratio, but not
impossible to do. So yes, you can cut a thread
without a leadscrew, just use the feed rack and pinion.
--Doozer