"Grant Erwin" wrote in message
...
SteveF wrote:
.. in practice can this be done with enough accuracy for something
like a replacement lead screw for a lathe?

No.

Hey! Not true, at all!

It's something of a chore to re-index a piece of threading work, but it's
not that bad. Takes patience and time, that's all.

Consider: Mark a thin scribe line down the length of the work to show the
rotational indexing position. Position your tool in the thread very near
the chuck, and lock the half-nuts. Then unchuck, and re-index the work in
rotation by the scribe, and longitudinally by leaving a small amount of the
already-threaded portion remaining beyond the chuck jaws, and using the
(never moved) bit to find the correct longitudinal position in the chuck.

Keep lost motion in mind, and snug the tool to the "cutting" face of the
thread (by moving the work to the tool) before each re-chuck.

LLoyd