Finish issues with single phase motors on an engine lathe? The rotating mass
of the motor, power transmission, gear train, spindle, chuck, & work will
negate any such issue. You guys are chasing windmills.

A 3/4 to 1 Hp motor would be fine. As for speed of 1140 vs 1725,
check/measure your all of the pulley reductions and see how the spindle
speeds compare to Southbends specs in "How to run a Lathe" or a old
Southbend brochure.

Single vs 3 phase? Single phase may be easier if it eliminates having to
start a converter every time. Wiring a drum switch for requires more wiring
with single, 7 leads as I recall. 3 phase makes for easier wiring. If you
have pushbutton start you will need to check the contactor for compatibility
either way, along with the coil voltage.

VFD on a Southbend, i thinks thats overkill, the three step pulley works
fine.

As for this oft mentioned theory of threaded spindle nose chucks unscrewing
when going into instant reverse... My 5 S/B's from 10" to 16" all with
threaded spindles this has never happened, and when I was in school many
years ago, our shop had 40 S/B heavy 10's with threaded spindles, and the
students often reversed rotating chucks, never saw a chuck come off, nor
were we warned not to do it.

With all the dire warnings I read here about threaded spindles, kinda makes
ya wonder how machinists survived until the advent of camlock spindles.....


Tony

"Steve Lusardi" wrote in message
...
Peter,
There have been a lot of replies to your post. I have a late model of your
machine. I bought it new from SB direct. I have changed motors. So my
experience is first hand. Anything more than 3/4 HP is a waste because it
won't couple to the chuck. The drive slips first. Most of those lathes
work
on single phase because of where they are used. This lathe is very light
and
flexes under load change. Single phase motors are not smooth. They
accelerate and decelerate under load at line frequency. This can be
observed
in finish cuts in high gear on your machine. Three phase motors are much
smoother and this finish problem goes away. I have a brand new OEM never
used 60 hz single phase motor for your machine that I will never use. You
are welcome to it, but I assure you a 3/4 HP 3 phase motor is much better.
Steve

"Peter Grey" wrote in message
ink.net...

Hello all,

I have a '33 11" SB lathe with a '31 Westinghouse 1/2 HP motor on it.
The
motor started acting up so I took it to my local motor shop who got it
running decently, but told me that it would cost a mint to do what needs
to be done to make it right (70 years of oil soaking into the winding
insulation and all that). While the motor works, it doesn't work as
well
as it should, and rather than spend more money than it's worth, I'd like
to replace it. The question is; with what?

I've been told that 1931 HP were bigger than 2006 HP and that I should
go
with a 3/4 or 1 HP motor to get similar work capacity. That's fine, and
my shop is wired for 110, 220 and I have both a rotary and static phase
converter. My lathe has a screw-on chuck so I don't have a need for
instant reversing (although the lathe is currently wired for reversing
and
I'd like to keep that capability). My question is, are there any
advantages to 220 or 220 3-phase over 110 when choosing a motor without
concern for instant reversing. IOW, do I get more real power with any
of
them, less power consumption, or smoother operation? Are there
advantages
or disadvantages that I haven't mentioned? Any types of motors I should
stay away from? Any types of motor that would be good for my
application?

I've done a RCM Google search and haven't been able to get these
questions
answered, but if anyone had a pointer to an appropriate web site, I'd be
happy to follow it. Keep in mind that I'm an electrical dunce (I had an
electrician install the RPC for my mill) so any conversation about
degaussing the flux capacitance in the field coil windings is likely to
leave me befuddled.

As usual, thanks for the advice and Happy New Year!

Regards,

Peter