On 2008-07-11, Stealth Pilot wrote:
On Thu, 10 Jul 2008 09:49:48 -0700 (PDT), Jim Wilkins
wrote:

[ ... ]

*At the end of the cut disengage the half nuts and back out the slide
exactly 0.100, ie to the next 0 at this point.

*Move the carriage back past the end of the work. Turn the slide in
one turn.

*Advance the compound a few thousandths. Engage the half nuts when the
proper line on the threading dial matches, or move the carriage to
meet it.

[ ... ]

thats the way to do it.
reversing the motor is awfully slow. on mine if I flip the switch into
reverse it just keeps running in the same direction.
If I stop it, then flip the switch I get reverse.
the stopping takes a while.

So you have a single phase motor. This is one of the places
where three phase wins -- you can "plug" reverse -- just switch into
reverse at the proper time (and quickly crank the cross-feed out during
the moment in which the spindle is stalled). Or -- if you have three
phase and a VFD, you can tune the ramp-down and ramp-up times to more
reasonably match the available power, and have a little more time to
crank out the cross slide -- if you *have* to run it in reverse instead
of disengaging the half nuts and cranking the carriage back. (You do
wind up in this situation when you're doing metric threads on an
imperial lathe, or vice versa.)

Enjoy,
DoN.

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