Choice B isn't that bad.

Mounting a DC motor is trivial, and you can build a DC powersupply for
pretty cheap if you go the Variac and Diode route. Sure this dosen't give
you constant speed, you will slow down a bit when you take a cut but it's
just too easy and cheap. At low speed a simple microswitch with a bit of
overtravel will stop you in the same place every time and if you want to get
fancy you can make it trip a relay that will automaticaly reverse the motor.
Another cool thing about a DC motor on your lathe, is that you can just
increase the speed as you crank in on the crossfeed while doing cutoff or
facing work :-)
This is the URL to an article I wrote for our Live Steam web site about
doing DC motors..
http://www.ggls.org/DCPower/
I had several of those old tape spindle motors like the one I put on my
lathe, and just finished mounting it on my 1J Bridgeport... Works like a
charm.. I'n 1:1 pulley mode I go from dead stop to 3000RPM..
A friend just finished sticking a 1/4HP DC motor on his drill press, he's
happy as a clam and he's headed for a DC motor on his Bridgeport.

If you don't have a threaded on chuck (I do ) Threading and boring on
the 'backside' is the way to go.

Dave

Correct on a non-metric lathe. If you have a metric lead-screw that's a
different story.

I went the el-cheapo route when I got my lathe and didn't spring for the
version with the half-nut. In my case (and yours) the procedure is to
_never_ disengage the half-nut. Instead you have to push the button to
stop the lathe at the end of the cut, roll it back by hand, re-do the cut,
etc.

I'm thinking of making myself a selection of left-cutting threading tools
so I can make the cut on the backside of the work with the tool moving to
the right -- this will allow me to start the tool by hand where it makes a
difference, and let it run off the end where it doesn't.

My other thought is to (a) make a crank handle for my spindle or the idler
pulley and turn the spindle by hand while cutting threads or (b) install a
DC motor, put an encoder on the spindle, and use a controller to stop the
motor at the right spot each time. Choice (a) will take less time to
make, longer to use each time, and carries the risk of forgetting to
disengage the crank for that "special excitement" that we all want to
avoid. Choice (b) promises to be lots of work.

--

Tim Wescott
Wescott Design Services
http://www.wescottdesign.com