On Fri, 14 Jan 2011 15:35:21 -0600, Terry
wrote:

My 13" SB metal lathe has been retrofitted with a PM DC motor. It's
not a treadmill motor, it's continuous duty according to the tag and
can handle up to 180 V. I assembled a speed control from a
treadmill-type board. Unfortunately it doesn't appear that the
controller provides enough oomph.

What I'd like to try instead is a 120v 20amp variable transformer,
output to a bridge rectifier, then filter the DC and send it to the
motor. By happy coincidence I have all the parts, total cost will be
simply a bit of time.

In typical RCM fashion I'm ignoring your question and answering one
you didn't ask. g Speed regulation will be poor with a simple power
supply. You'd be much better off with a DC motor drive similar to
this:
http://www.galco.com/scripts/cgiip.e...um=KBIC-120-KB

--
Ned Simmons