Converting an Orac lathe

Hi all,
If anyone is thinking of upgrading a Denford Orac to PC control, I recently
stripped mine and found out the following:

The steppers are 3V 3.1A, 200 step/rev, 8 wire.
The stepper drives are in a nice 19" rack and are made by Parker Hannifin,
model SD3. A data sheet can be found here:
http://www.compumotor.com/manuals/Digiplan/SD/SD.htm#SD2 Step and direction
signals go into the rack on two screened cables (convenient!)
Spindle is a standard 3 phase 240V 1/2hp motor driver by a rather strange
VFD. Pins on the VFD are
L,N,E - mains in
A,B,C - 3ph out
7,8 - connect these together via a relay to turn the drive on
9 - speed input gnd
10 - speed - 0V=min speed, 12V=max speed
If you don't have an isolated +12V then +12V can be stolen from pin 14 of
any of the 40xx chips on the top board.
WARNING: the inputs are at 120VDC above earth! They must be isolated from
any other electronics on pain of death (both yours and anything connected)

Resolution appears to be about 1/4 thou per step.

That is all so far. If you have any other questions, let me know.

Les