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.

Sigh!

As already mentioned, adding an idler gear to the train (as long
as you can find a place on the crowsfoot to mount it (or whatever the
equivalent on the Enco lathe might be)) will accomplish the reversal, if
not as conveniently as the tumbler gears on larger lathes.

so, besides lh threads, what would this reverse mode be good for? probably
a dumb question(?). you could take cuts in both directions under power, what
else, tram under power? you can reverse the motor for that. Thanks! --Loren

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.

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
from the outside towards the center, I have to reverse the leadscrew.
(Same for a parting cut.) I think that this is so you can cut from the
end towards a shoulder, then face out to the edge just by switch from
power longitudinal to power crossfeed for a finish pass.

Enjoy,
DoN.
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