In article , DoN. Nichols wrote:
In article vzPDb.564096$HS4.4277225@attbi_s01,
Loren Coe wrote:
In article , DoN. Nichols wrote:
In article 8SpCb.323522$Dw6.1095317@attbi_s02,
[ ... ]
The tumbler gears reverse the leadscrew on any lathe fitted with
them (unfortunately, not the one in question).

nor my Grizzly 3n1 (4015), not too surprising, i guess, but never had
a reason to wonder until now. what i thought might be a reverse is
simply a clutch which allows you to do manual feed using the lead
screw.
....
so, besides lh threads, what would this reverse mode be good for?
.....
Well ... I sometimes use it for turning away from a shoulder
(after doing most of the work towards it, and moving by hand the last
few thousandths. Doing a finish pass in reverse makes sure that the
finish from the shoulder on out is the same -- which you lose with hand
feeding part of the distance.

interesting, and your manual feed likely doesn't use the lead screw, but
a linear toothed plate, right? this is a basic design feature that marks
the very low end machine, the lack of, i mean. my manual feed requires
turning a handwheel on the end of the lead screw. not very handy.

at least the 9X20 has this feature, but makes me wonder about the handle
at the head end of the lead screw, likely just a clutch like mine. this
makes some sense on my 3n1, since the handwheel turns with the screw.

Also -- if your lathe has power cross-feed, it allows you to
choose between facing from the outside towards the center, or from the
center towards the outside. On my 12x24" Clausing, if I want to face
.... Enjoy, DoN.

that's the reason for a 2nd "lead" screw, right? i swear i have seen
a 3rd, but don't know where/when. well, this thread has been good for
me, thanks to all. Happy Holidays, --Loren