Is there a decent small format 3 phase motor that develops its best torque
and HP in the 30-120hz range? Typically small tools needing a compact motor
use a universal brush motor. For example your typical mini lathe. My
little 7x10 (now 7x16) has a universal brush motor. I've been tinkering on
and off over the last couple years with converting it to CNC. I finished
the Z motor and lead hardware a long time ago, and I finally figured out how
I want to do the X. I've got a few little trinket parts on order, and I'll
machine the saddle and brand new t-slot table (for gang tooling) to fit
shortly when they arrive.

One of the things I want to do is improve the spindle motor setup when I get
to that point. The universal brush motor with its Chinese speed control
works ok, but its not wonderful. For manual turning if it bogs down I just
reach over and turn the pot. An AC servo is a little more than I want to
put on the machine for a spindle motor. At about half the cost I can put on
a small VFD, a 3 phase motor, and a cooling fan. I think I know that there
are inherent reasons why AC induction motors tend to be much larger than
universal brush motors for similar gross power ratings, but I can't believe
a 1/3 to 1/2 hp 3 phase motor can't be made a lot smaller than say a 1 or 2
hp motor. I intend to make a mounting plate for the motor anyway, so I
could certainly use a physically larger motor, but it just feels so
"sledgehammer inelegant" to me.

Its a really light weight machine still so a spindle motor with any more
power (and I have a few laying around) might allow me to program code that
would allow the machine to tear itself apart. Its still just a light
weight, but I have a few parts I could make and sell for a small profit if I
could just semi-automate them and walk away. Besides, I am having fun
converting this little toy lathe over to CNC operation.